]>
Commit | Line | Data |
---|---|---|
333d7d37 TA |
1 | Git User Manual |
2 | _______________ | |
99eaefdd BF |
3 | |
4 | Git is a fast distributed revision control system. | |
5 | ||
02783075 | 6 | This manual is designed to be readable by someone with basic UNIX |
2de9b711 | 7 | command-line skills, but no previous knowledge of Git. |
d19fbc3c | 8 | |
2624d9a5 BF |
9 | <<repositories-and-branches>> and <<exploring-git-history>> explain how |
10 | to fetch and study a project using git--read these chapters to learn how | |
11 | to build and test a particular version of a software project, search for | |
12 | regressions, and so on. | |
ef89f701 | 13 | |
2624d9a5 | 14 | People needing to do actual development will also want to read |
aa971cb9 | 15 | <<Developing-With-git>> and <<sharing-development>>. |
6bd9b682 BF |
16 | |
17 | Further chapters cover more specialized topics. | |
18 | ||
d19fbc3c | 19 | Comprehensive reference documentation is available through the man |
b3d98887 | 20 | pages, or linkgit:git-help[1] command. For example, for the command |
1249d8ad | 21 | `git clone <repo>`, you can either use: |
d19fbc3c BF |
22 | |
23 | ------------------------------------------------ | |
24 | $ man git-clone | |
25 | ------------------------------------------------ | |
26 | ||
b3d98887 CC |
27 | or: |
28 | ||
29 | ------------------------------------------------ | |
30 | $ git help clone | |
31 | ------------------------------------------------ | |
32 | ||
33 | With the latter, you can use the manual viewer of your choice; see | |
34 | linkgit:git-help[1] for more information. | |
35 | ||
2de9b711 | 36 | See also <<git-quick-start>> for a brief overview of Git commands, |
2624d9a5 | 37 | without any explanation. |
b181d57f | 38 | |
99f171bb | 39 | Finally, see <<todo>> for ways that you can help make this manual more |
2624d9a5 | 40 | complete. |
b181d57f | 41 | |
b181d57f | 42 | |
e34caace | 43 | [[repositories-and-branches]] |
d19fbc3c BF |
44 | Repositories and Branches |
45 | ========================= | |
46 | ||
e34caace | 47 | [[how-to-get-a-git-repository]] |
2de9b711 | 48 | How to get a Git repository |
d19fbc3c BF |
49 | --------------------------- |
50 | ||
2de9b711 | 51 | It will be useful to have a Git repository to experiment with as you |
d19fbc3c BF |
52 | read this manual. |
53 | ||
5162e697 | 54 | The best way to get one is by using the linkgit:git-clone[1] command to |
a5f90f31 BF |
55 | download a copy of an existing repository. If you don't already have a |
56 | project in mind, here are some interesting examples: | |
d19fbc3c BF |
57 | |
58 | ------------------------------------------------ | |
4b9ced27 | 59 | # Git itself (approx. 40MB download): |
d19fbc3c | 60 | $ git clone git://git.kernel.org/pub/scm/git/git.git |
4b9ced27 TK |
61 | # the Linux kernel (approx. 640MB download): |
62 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git | |
d19fbc3c BF |
63 | ------------------------------------------------ |
64 | ||
65 | The initial clone may be time-consuming for a large project, but you | |
66 | will only need to clone once. | |
67 | ||
283efb01 TK |
68 | The clone command creates a new directory named after the project |
69 | (`git` or `linux` in the examples above). After you cd into this | |
d19fbc3c | 70 | directory, you will see that it contains a copy of the project files, |
0c4a33b5 | 71 | called the <<def_working_tree,working tree>>, together with a special |
1249d8ad | 72 | top-level directory named `.git`, which contains all the information |
0c4a33b5 | 73 | about the history of the project. |
d19fbc3c | 74 | |
e34caace | 75 | [[how-to-check-out]] |
d19fbc3c BF |
76 | How to check out a different version of a project |
77 | ------------------------------------------------- | |
78 | ||
a2ef9d63 BF |
79 | Git is best thought of as a tool for storing the history of a collection |
80 | of files. It stores the history as a compressed collection of | |
2de9b711 | 81 | interrelated snapshots of the project's contents. In Git each such |
a2ef9d63 | 82 | version is called a <<def_commit,commit>>. |
d19fbc3c | 83 | |
0c4a33b5 BF |
84 | Those snapshots aren't necessarily all arranged in a single line from |
85 | oldest to newest; instead, work may simultaneously proceed along | |
57283291 | 86 | parallel lines of development, called <<def_branch,branches>>, which may |
0c4a33b5 BF |
87 | merge and diverge. |
88 | ||
2de9b711 | 89 | A single Git repository can track development on multiple branches. It |
0c4a33b5 | 90 | does this by keeping a list of <<def_head,heads>> which reference the |
5162e697 | 91 | latest commit on each branch; the linkgit:git-branch[1] command shows |
81b6c950 | 92 | you the list of branch heads: |
d19fbc3c BF |
93 | |
94 | ------------------------------------------------ | |
95 | $ git branch | |
96 | * master | |
97 | ------------------------------------------------ | |
98 | ||
4f752407 BF |
99 | A freshly cloned repository contains a single branch head, by default |
100 | named "master", with the working directory initialized to the state of | |
101 | the project referred to by that branch head. | |
d19fbc3c | 102 | |
81b6c950 BF |
103 | Most projects also use <<def_tag,tags>>. Tags, like heads, are |
104 | references into the project's history, and can be listed using the | |
5162e697 | 105 | linkgit:git-tag[1] command: |
d19fbc3c BF |
106 | |
107 | ------------------------------------------------ | |
108 | $ git tag -l | |
109 | v2.6.11 | |
110 | v2.6.11-tree | |
111 | v2.6.12 | |
112 | v2.6.12-rc2 | |
113 | v2.6.12-rc3 | |
114 | v2.6.12-rc4 | |
115 | v2.6.12-rc5 | |
116 | v2.6.12-rc6 | |
117 | v2.6.13 | |
118 | ... | |
119 | ------------------------------------------------ | |
120 | ||
fe4b3e59 | 121 | Tags are expected to always point at the same version of a project, |
81b6c950 | 122 | while heads are expected to advance as development progresses. |
fe4b3e59 | 123 | |
81b6c950 | 124 | Create a new branch head pointing to one of these versions and check it |
5162e697 | 125 | out using linkgit:git-checkout[1]: |
d19fbc3c BF |
126 | |
127 | ------------------------------------------------ | |
128 | $ git checkout -b new v2.6.13 | |
129 | ------------------------------------------------ | |
130 | ||
131 | The working directory then reflects the contents that the project had | |
5162e697 | 132 | when it was tagged v2.6.13, and linkgit:git-branch[1] shows two |
d19fbc3c BF |
133 | branches, with an asterisk marking the currently checked-out branch: |
134 | ||
135 | ------------------------------------------------ | |
136 | $ git branch | |
137 | master | |
138 | * new | |
139 | ------------------------------------------------ | |
140 | ||
141 | If you decide that you'd rather see version 2.6.17, you can modify | |
142 | the current branch to point at v2.6.17 instead, with | |
143 | ||
144 | ------------------------------------------------ | |
145 | $ git reset --hard v2.6.17 | |
146 | ------------------------------------------------ | |
147 | ||
81b6c950 | 148 | Note that if the current branch head was your only reference to a |
d19fbc3c | 149 | particular point in history, then resetting that branch may leave you |
81b6c950 BF |
150 | with no way to find the history it used to point to; so use this command |
151 | carefully. | |
d19fbc3c | 152 | |
e34caace | 153 | [[understanding-commits]] |
d19fbc3c BF |
154 | Understanding History: Commits |
155 | ------------------------------ | |
156 | ||
157 | Every change in the history of a project is represented by a commit. | |
5162e697 | 158 | The linkgit:git-show[1] command shows the most recent commit on the |
d19fbc3c BF |
159 | current branch: |
160 | ||
161 | ------------------------------------------------ | |
162 | $ git show | |
e2618ff4 BF |
163 | commit 17cf781661e6d38f737f15f53ab552f1e95960d7 |
164 | Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)> | |
165 | Date: Tue Apr 19 14:11:06 2005 -0700 | |
166 | ||
167 | Remove duplicate getenv(DB_ENVIRONMENT) call | |
168 | ||
169 | Noted by Tony Luck. | |
170 | ||
171 | diff --git a/init-db.c b/init-db.c | |
172 | index 65898fa..b002dc6 100644 | |
173 | --- a/init-db.c | |
174 | +++ b/init-db.c | |
175 | @@ -7,7 +7,7 @@ | |
d19fbc3c | 176 | |
e2618ff4 BF |
177 | int main(int argc, char **argv) |
178 | { | |
179 | - char *sha1_dir = getenv(DB_ENVIRONMENT), *path; | |
180 | + char *sha1_dir, *path; | |
181 | int len, i; | |
182 | ||
183 | if (mkdir(".git", 0755) < 0) { | |
d19fbc3c BF |
184 | ------------------------------------------------ |
185 | ||
186 | As you can see, a commit shows who made the latest change, what they | |
187 | did, and why. | |
188 | ||
35121930 | 189 | Every commit has a 40-hexdigit id, sometimes called the "object name" or the |
1249d8ad | 190 | "SHA-1 id", shown on the first line of the `git show` output. You can usually |
35121930 BF |
191 | refer to a commit by a shorter name, such as a tag or a branch name, but this |
192 | longer name can also be useful. Most importantly, it is a globally unique | |
193 | name for this commit: so if you tell somebody else the object name (for | |
194 | example in email), then you are guaranteed that name will refer to the same | |
195 | commit in their repository that it does in yours (assuming their repository | |
196 | has that commit at all). Since the object name is computed as a hash over the | |
197 | contents of the commit, you are guaranteed that the commit can never change | |
198 | without its name also changing. | |
199 | ||
2de9b711 | 200 | In fact, in <<git-concepts>> we shall see that everything stored in Git |
35121930 BF |
201 | history, including file data and directory contents, is stored in an object |
202 | with a name that is a hash of its contents. | |
d19fbc3c | 203 | |
e34caace | 204 | [[understanding-reachability]] |
d19fbc3c BF |
205 | Understanding history: commits, parents, and reachability |
206 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
207 | ||
208 | Every commit (except the very first commit in a project) also has a | |
209 | parent commit which shows what happened before this commit. | |
210 | Following the chain of parents will eventually take you back to the | |
211 | beginning of the project. | |
212 | ||
2de9b711 | 213 | However, the commits do not form a simple list; Git allows lines of |
d19fbc3c BF |
214 | development to diverge and then reconverge, and the point where two |
215 | lines of development reconverge is called a "merge". The commit | |
216 | representing a merge can therefore have more than one parent, with | |
217 | each parent representing the most recent commit on one of the lines | |
218 | of development leading to that point. | |
219 | ||
5162e697 | 220 | The best way to see how this works is using the linkgit:gitk[1] |
2de9b711 TA |
221 | command; running gitk now on a Git repository and looking for merge |
222 | commits will help understand how the Git organizes history. | |
d19fbc3c BF |
223 | |
224 | In the following, we say that commit X is "reachable" from commit Y | |
225 | if commit X is an ancestor of commit Y. Equivalently, you could say | |
02783075 | 226 | that Y is a descendant of X, or that there is a chain of parents |
d19fbc3c BF |
227 | leading from commit Y to commit X. |
228 | ||
e34caace | 229 | [[history-diagrams]] |
3dff5379 PR |
230 | Understanding history: History diagrams |
231 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 232 | |
2de9b711 | 233 | We will sometimes represent Git history using diagrams like the one |
d19fbc3c BF |
234 | below. Commits are shown as "o", and the links between them with |
235 | lines drawn with - / and \. Time goes left to right: | |
236 | ||
1dc71a91 BF |
237 | |
238 | ................................................ | |
d19fbc3c BF |
239 | o--o--o <-- Branch A |
240 | / | |
241 | o--o--o <-- master | |
242 | \ | |
243 | o--o--o <-- Branch B | |
1dc71a91 | 244 | ................................................ |
d19fbc3c BF |
245 | |
246 | If we need to talk about a particular commit, the character "o" may | |
247 | be replaced with another letter or number. | |
248 | ||
e34caace | 249 | [[what-is-a-branch]] |
d19fbc3c BF |
250 | Understanding history: What is a branch? |
251 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
252 | ||
81b6c950 BF |
253 | When we need to be precise, we will use the word "branch" to mean a line |
254 | of development, and "branch head" (or just "head") to mean a reference | |
255 | to the most recent commit on a branch. In the example above, the branch | |
256 | head named "A" is a pointer to one particular commit, but we refer to | |
257 | the line of three commits leading up to that point as all being part of | |
d19fbc3c BF |
258 | "branch A". |
259 | ||
81b6c950 BF |
260 | However, when no confusion will result, we often just use the term |
261 | "branch" both for branches and for branch heads. | |
d19fbc3c | 262 | |
e34caace | 263 | [[manipulating-branches]] |
d19fbc3c BF |
264 | Manipulating branches |
265 | --------------------- | |
266 | ||
267 | Creating, deleting, and modifying branches is quick and easy; here's | |
268 | a summary of the commands: | |
269 | ||
1249d8ad | 270 | `git branch`:: |
d19fbc3c | 271 | list all branches |
1249d8ad TK |
272 | `git branch <branch>`:: |
273 | create a new branch named `<branch>`, referencing the same | |
d19fbc3c | 274 | point in history as the current branch |
1249d8ad TK |
275 | `git branch <branch> <start-point>`:: |
276 | create a new branch named `<branch>`, referencing | |
277 | `<start-point>`, which may be specified any way you like, | |
d19fbc3c | 278 | including using a branch name or a tag name |
1249d8ad TK |
279 | `git branch -d <branch>`:: |
280 | delete the branch `<branch>`; if the branch you are deleting | |
c64415e2 BF |
281 | points to a commit which is not reachable from the current |
282 | branch, this command will fail with a warning. | |
1249d8ad | 283 | `git branch -D <branch>`:: |
d19fbc3c BF |
284 | even if the branch points to a commit not reachable |
285 | from the current branch, you may know that that commit | |
286 | is still reachable from some other branch or tag. In that | |
2de9b711 | 287 | case it is safe to use this command to force Git to delete |
d19fbc3c | 288 | the branch. |
1249d8ad TK |
289 | `git checkout <branch>`:: |
290 | make the current branch `<branch>`, updating the working | |
291 | directory to reflect the version referenced by `<branch>` | |
292 | `git checkout -b <new> <start-point>`:: | |
293 | create a new branch `<new>` referencing `<start-point>`, and | |
d19fbc3c BF |
294 | check it out. |
295 | ||
72a76c95 | 296 | The special symbol "HEAD" can always be used to refer to the current |
1249d8ad TK |
297 | branch. In fact, Git uses a file named `HEAD` in the `.git` directory |
298 | to remember which branch is current: | |
72a76c95 BF |
299 | |
300 | ------------------------------------------------ | |
301 | $ cat .git/HEAD | |
302 | ref: refs/heads/master | |
303 | ------------------------------------------------ | |
304 | ||
25d9f3fa | 305 | [[detached-head]] |
72a76c95 BF |
306 | Examining an old version without creating a new branch |
307 | ------------------------------------------------------ | |
308 | ||
6127c086 | 309 | The `git checkout` command normally expects a branch head, but will also |
72a76c95 BF |
310 | accept an arbitrary commit; for example, you can check out the commit |
311 | referenced by a tag: | |
312 | ||
313 | ------------------------------------------------ | |
314 | $ git checkout v2.6.17 | |
95f9be55 TA |
315 | Note: checking out 'v2.6.17'. |
316 | ||
317 | You are in 'detached HEAD' state. You can look around, make experimental | |
318 | changes and commit them, and you can discard any commits you make in this | |
319 | state without impacting any branches by performing another checkout. | |
320 | ||
321 | If you want to create a new branch to retain commits you create, you may | |
322 | do so (now or later) by using -b with the checkout command again. Example: | |
323 | ||
324 | git checkout -b new_branch_name | |
325 | ||
72a76c95 BF |
326 | HEAD is now at 427abfa... Linux v2.6.17 |
327 | ------------------------------------------------ | |
328 | ||
a6e5ef7d | 329 | The HEAD then refers to the SHA-1 of the commit instead of to a branch, |
72a76c95 BF |
330 | and git branch shows that you are no longer on a branch: |
331 | ||
332 | ------------------------------------------------ | |
333 | $ cat .git/HEAD | |
334 | 427abfa28afedffadfca9dd8b067eb6d36bac53f | |
953f3d6f | 335 | $ git branch |
95f9be55 | 336 | * (detached from v2.6.17) |
72a76c95 BF |
337 | master |
338 | ------------------------------------------------ | |
339 | ||
340 | In this case we say that the HEAD is "detached". | |
341 | ||
953f3d6f BF |
342 | This is an easy way to check out a particular version without having to |
343 | make up a name for the new branch. You can still create a new branch | |
344 | (or tag) for this version later if you decide to. | |
d19fbc3c | 345 | |
e34caace | 346 | [[examining-remote-branches]] |
d19fbc3c BF |
347 | Examining branches from a remote repository |
348 | ------------------------------------------- | |
349 | ||
350 | The "master" branch that was created at the time you cloned is a copy | |
351 | of the HEAD in the repository that you cloned from. That repository | |
352 | may also have had other branches, though, and your local repository | |
66a062a1 MM |
353 | keeps branches which track each of those remote branches, called |
354 | remote-tracking branches, which you | |
1249d8ad | 355 | can view using the `-r` option to linkgit:git-branch[1]: |
d19fbc3c BF |
356 | |
357 | ------------------------------------------------ | |
358 | $ git branch -r | |
359 | origin/HEAD | |
360 | origin/html | |
361 | origin/maint | |
362 | origin/man | |
363 | origin/master | |
364 | origin/next | |
365 | origin/pu | |
366 | origin/todo | |
367 | ------------------------------------------------ | |
368 | ||
66a062a1 MM |
369 | In this example, "origin" is called a remote repository, or "remote" |
370 | for short. The branches of this repository are called "remote | |
371 | branches" from our point of view. The remote-tracking branches listed | |
372 | above were created based on the remote branches at clone time and will | |
1249d8ad | 373 | be updated by `git fetch` (hence `git pull`) and `git push`. See |
66a062a1 MM |
374 | <<Updating-a-repository-With-git-fetch>> for details. |
375 | ||
45dfd403 JN |
376 | You might want to build on one of these remote-tracking branches |
377 | on a branch of your own, just as you would for a tag: | |
d19fbc3c BF |
378 | |
379 | ------------------------------------------------ | |
380 | $ git checkout -b my-todo-copy origin/todo | |
381 | ------------------------------------------------ | |
382 | ||
1249d8ad | 383 | You can also check out `origin/todo` directly to examine it or |
45dfd403 JN |
384 | write a one-off patch. See <<detached-head,detached head>>. |
385 | ||
2de9b711 | 386 | Note that the name "origin" is just the name that Git uses by default |
d19fbc3c BF |
387 | to refer to the repository that you cloned from. |
388 | ||
389 | [[how-git-stores-references]] | |
f60b9642 BF |
390 | Naming branches, tags, and other references |
391 | ------------------------------------------- | |
d19fbc3c BF |
392 | |
393 | Branches, remote-tracking branches, and tags are all references to | |
f60b9642 | 394 | commits. All references are named with a slash-separated path name |
1249d8ad | 395 | starting with `refs`; the names we've been using so far are actually |
f60b9642 | 396 | shorthand: |
d19fbc3c | 397 | |
1249d8ad TK |
398 | - The branch `test` is short for `refs/heads/test`. |
399 | - The tag `v2.6.18` is short for `refs/tags/v2.6.18`. | |
400 | - `origin/master` is short for `refs/remotes/origin/master`. | |
d19fbc3c | 401 | |
f60b9642 BF |
402 | The full name is occasionally useful if, for example, there ever |
403 | exists a tag and a branch with the same name. | |
d19fbc3c | 404 | |
1249d8ad | 405 | (Newly created refs are actually stored in the `.git/refs` directory, |
fc74ecc1 BF |
406 | under the path given by their name. However, for efficiency reasons |
407 | they may also be packed together in a single file; see | |
5162e697 | 408 | linkgit:git-pack-refs[1]). |
fc74ecc1 | 409 | |
c64415e2 BF |
410 | As another useful shortcut, the "HEAD" of a repository can be referred |
411 | to just using the name of that repository. So, for example, "origin" | |
412 | is usually a shortcut for the HEAD branch in the repository "origin". | |
d19fbc3c | 413 | |
2de9b711 | 414 | For the complete list of paths which Git checks for references, and |
f60b9642 BF |
415 | the order it uses to decide which to choose when there are multiple |
416 | references with the same shorthand name, see the "SPECIFYING | |
9d83e382 | 417 | REVISIONS" section of linkgit:gitrevisions[7]. |
d19fbc3c | 418 | |
aa971cb9 | 419 | [[Updating-a-repository-With-git-fetch]] |
6127c086 | 420 | Updating a repository with git fetch |
d19fbc3c BF |
421 | ------------------------------------ |
422 | ||
423 | Eventually the developer cloned from will do additional work in her | |
424 | repository, creating new commits and advancing the branches to point | |
425 | at the new commits. | |
426 | ||
1249d8ad | 427 | The command `git fetch`, with no arguments, will update all of the |
d19fbc3c BF |
428 | remote-tracking branches to the latest version found in her |
429 | repository. It will not touch any of your own branches--not even the | |
430 | "master" branch that was created for you on clone. | |
431 | ||
e34caace | 432 | [[fetching-branches]] |
d5cd5de4 BF |
433 | Fetching branches from other repositories |
434 | ----------------------------------------- | |
435 | ||
436 | You can also track branches from repositories other than the one you | |
5162e697 | 437 | cloned from, using linkgit:git-remote[1]: |
d5cd5de4 BF |
438 | |
439 | ------------------------------------------------- | |
34a25d4c TK |
440 | $ git remote add staging git://git.kernel.org/.../gregkh/staging.git |
441 | $ git fetch staging | |
442 | ... | |
443 | From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging | |
444 | * [new branch] master -> staging/master | |
445 | * [new branch] staging-linus -> staging/staging-linus | |
446 | * [new branch] staging-next -> staging/staging-next | |
d5cd5de4 BF |
447 | ------------------------------------------------- |
448 | ||
449 | New remote-tracking branches will be stored under the shorthand name | |
34a25d4c | 450 | that you gave `git remote add`, in this case `staging`: |
d5cd5de4 BF |
451 | |
452 | ------------------------------------------------- | |
453 | $ git branch -r | |
34a25d4c TK |
454 | origin/HEAD -> origin/master |
455 | origin/master | |
456 | staging/master | |
457 | staging/staging-linus | |
458 | staging/staging-next | |
d5cd5de4 BF |
459 | ------------------------------------------------- |
460 | ||
1249d8ad TK |
461 | If you run `git fetch <remote>` later, the remote-tracking branches |
462 | for the named `<remote>` will be updated. | |
d5cd5de4 | 463 | |
1249d8ad | 464 | If you examine the file `.git/config`, you will see that Git has added |
d5cd5de4 BF |
465 | a new stanza: |
466 | ||
467 | ------------------------------------------------- | |
468 | $ cat .git/config | |
469 | ... | |
34a25d4c TK |
470 | [remote "staging"] |
471 | url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git | |
472 | fetch = +refs/heads/*:refs/remotes/staging/* | |
d5cd5de4 BF |
473 | ... |
474 | ------------------------------------------------- | |
475 | ||
2de9b711 | 476 | This is what causes Git to track the remote's branches; you may modify |
1249d8ad | 477 | or delete these configuration options by editing `.git/config` with a |
fc90c536 | 478 | text editor. (See the "CONFIGURATION FILE" section of |
5162e697 | 479 | linkgit:git-config[1] for details.) |
d5cd5de4 | 480 | |
e34caace | 481 | [[exploring-git-history]] |
2de9b711 | 482 | Exploring Git history |
d19fbc3c BF |
483 | ===================== |
484 | ||
485 | Git is best thought of as a tool for storing the history of a | |
486 | collection of files. It does this by storing compressed snapshots of | |
1130845b | 487 | the contents of a file hierarchy, together with "commits" which show |
d19fbc3c BF |
488 | the relationships between these snapshots. |
489 | ||
490 | Git provides extremely flexible and fast tools for exploring the | |
491 | history of a project. | |
492 | ||
aacd404e | 493 | We start with one specialized tool that is useful for finding the |
d19fbc3c BF |
494 | commit that introduced a bug into a project. |
495 | ||
e34caace | 496 | [[using-bisect]] |
d19fbc3c BF |
497 | How to use bisect to find a regression |
498 | -------------------------------------- | |
499 | ||
500 | Suppose version 2.6.18 of your project worked, but the version at | |
501 | "master" crashes. Sometimes the best way to find the cause of such a | |
502 | regression is to perform a brute-force search through the project's | |
503 | history to find the particular commit that caused the problem. The | |
5162e697 | 504 | linkgit:git-bisect[1] command can help you do this: |
d19fbc3c BF |
505 | |
506 | ------------------------------------------------- | |
507 | $ git bisect start | |
508 | $ git bisect good v2.6.18 | |
509 | $ git bisect bad master | |
510 | Bisecting: 3537 revisions left to test after this | |
511 | [65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6] | |
512 | ------------------------------------------------- | |
513 | ||
1249d8ad | 514 | If you run `git branch` at this point, you'll see that Git has |
0e25790f CC |
515 | temporarily moved you in "(no branch)". HEAD is now detached from any |
516 | branch and points directly to a commit (with commit id 65934...) that | |
517 | is reachable from "master" but not from v2.6.18. Compile and test it, | |
518 | and see whether it crashes. Assume it does crash. Then: | |
d19fbc3c BF |
519 | |
520 | ------------------------------------------------- | |
521 | $ git bisect bad | |
522 | Bisecting: 1769 revisions left to test after this | |
523 | [7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings | |
524 | ------------------------------------------------- | |
525 | ||
2de9b711 | 526 | checks out an older version. Continue like this, telling Git at each |
d19fbc3c BF |
527 | stage whether the version it gives you is good or bad, and notice |
528 | that the number of revisions left to test is cut approximately in | |
529 | half each time. | |
530 | ||
531 | After about 13 tests (in this case), it will output the commit id of | |
532 | the guilty commit. You can then examine the commit with | |
5162e697 | 533 | linkgit:git-show[1], find out who wrote it, and mail them your bug |
d19fbc3c BF |
534 | report with the commit id. Finally, run |
535 | ||
536 | ------------------------------------------------- | |
537 | $ git bisect reset | |
538 | ------------------------------------------------- | |
539 | ||
0e25790f | 540 | to return you to the branch you were on before. |
d19fbc3c | 541 | |
6127c086 | 542 | Note that the version which `git bisect` checks out for you at each |
d19fbc3c BF |
543 | point is just a suggestion, and you're free to try a different |
544 | version if you think it would be a good idea. For example, | |
545 | occasionally you may land on a commit that broke something unrelated; | |
546 | run | |
547 | ||
548 | ------------------------------------------------- | |
04483524 | 549 | $ git bisect visualize |
d19fbc3c BF |
550 | ------------------------------------------------- |
551 | ||
552 | which will run gitk and label the commit it chose with a marker that | |
843c81dc | 553 | says "bisect". Choose a safe-looking commit nearby, note its commit |
d19fbc3c BF |
554 | id, and check it out with: |
555 | ||
556 | ------------------------------------------------- | |
557 | $ git reset --hard fb47ddb2db... | |
558 | ------------------------------------------------- | |
559 | ||
1249d8ad | 560 | then test, run `bisect good` or `bisect bad` as appropriate, and |
d19fbc3c BF |
561 | continue. |
562 | ||
1249d8ad TK |
563 | Instead of `git bisect visualize` and then `git reset --hard |
564 | fb47ddb2db...`, you might just want to tell Git that you want to skip | |
0e25790f CC |
565 | the current commit: |
566 | ||
567 | ------------------------------------------------- | |
568 | $ git bisect skip | |
569 | ------------------------------------------------- | |
570 | ||
2de9b711 | 571 | In this case, though, Git may not eventually be able to tell the first |
a0178ae2 | 572 | bad one between some first skipped commits and a later bad commit. |
0e25790f CC |
573 | |
574 | There are also ways to automate the bisecting process if you have a | |
575 | test script that can tell a good from a bad commit. See | |
1249d8ad TK |
576 | linkgit:git-bisect[1] for more information about this and other `git |
577 | bisect` features. | |
0e25790f | 578 | |
e34caace | 579 | [[naming-commits]] |
d19fbc3c BF |
580 | Naming commits |
581 | -------------- | |
582 | ||
583 | We have seen several ways of naming commits already: | |
584 | ||
d55ae921 | 585 | - 40-hexdigit object name |
d19fbc3c BF |
586 | - branch name: refers to the commit at the head of the given |
587 | branch | |
588 | - tag name: refers to the commit pointed to by the given tag | |
589 | (we've seen branches and tags are special cases of | |
590 | <<how-git-stores-references,references>>). | |
591 | - HEAD: refers to the head of the current branch | |
592 | ||
eb6ae7f4 | 593 | There are many more; see the "SPECIFYING REVISIONS" section of the |
9d83e382 | 594 | linkgit:gitrevisions[7] man page for the complete list of ways to |
d19fbc3c BF |
595 | name revisions. Some examples: |
596 | ||
597 | ------------------------------------------------- | |
d55ae921 | 598 | $ git show fb47ddb2 # the first few characters of the object name |
d19fbc3c BF |
599 | # are usually enough to specify it uniquely |
600 | $ git show HEAD^ # the parent of the HEAD commit | |
601 | $ git show HEAD^^ # the grandparent | |
602 | $ git show HEAD~4 # the great-great-grandparent | |
603 | ------------------------------------------------- | |
604 | ||
605 | Recall that merge commits may have more than one parent; by default, | |
1249d8ad | 606 | `^` and `~` follow the first parent listed in the commit, but you can |
d19fbc3c BF |
607 | also choose: |
608 | ||
609 | ------------------------------------------------- | |
610 | $ git show HEAD^1 # show the first parent of HEAD | |
611 | $ git show HEAD^2 # show the second parent of HEAD | |
612 | ------------------------------------------------- | |
613 | ||
614 | In addition to HEAD, there are several other special names for | |
615 | commits: | |
616 | ||
617 | Merges (to be discussed later), as well as operations such as | |
6127c086 | 618 | `git reset`, which change the currently checked-out commit, generally |
d19fbc3c BF |
619 | set ORIG_HEAD to the value HEAD had before the current operation. |
620 | ||
6127c086 FC |
621 | The `git fetch` operation always stores the head of the last fetched |
622 | branch in FETCH_HEAD. For example, if you run `git fetch` without | |
d19fbc3c BF |
623 | specifying a local branch as the target of the operation |
624 | ||
625 | ------------------------------------------------- | |
626 | $ git fetch git://example.com/proj.git theirbranch | |
627 | ------------------------------------------------- | |
628 | ||
629 | the fetched commits will still be available from FETCH_HEAD. | |
630 | ||
631 | When we discuss merges we'll also see the special name MERGE_HEAD, | |
632 | which refers to the other branch that we're merging in to the current | |
633 | branch. | |
634 | ||
5162e697 | 635 | The linkgit:git-rev-parse[1] command is a low-level command that is |
d55ae921 BF |
636 | occasionally useful for translating some name for a commit to the object |
637 | name for that commit: | |
aec053bb BF |
638 | |
639 | ------------------------------------------------- | |
640 | $ git rev-parse origin | |
641 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
642 | ------------------------------------------------- | |
643 | ||
e34caace | 644 | [[creating-tags]] |
d19fbc3c BF |
645 | Creating tags |
646 | ------------- | |
647 | ||
648 | We can also create a tag to refer to a particular commit; after | |
649 | running | |
650 | ||
651 | ------------------------------------------------- | |
04483524 | 652 | $ git tag stable-1 1b2e1d63ff |
d19fbc3c BF |
653 | ------------------------------------------------- |
654 | ||
1249d8ad | 655 | You can use `stable-1` to refer to the commit 1b2e1d63ff. |
d19fbc3c | 656 | |
c64415e2 BF |
657 | This creates a "lightweight" tag. If you would also like to include a |
658 | comment with the tag, and possibly sign it cryptographically, then you | |
5162e697 | 659 | should create a tag object instead; see the linkgit:git-tag[1] man page |
c64415e2 | 660 | for details. |
d19fbc3c | 661 | |
e34caace | 662 | [[browsing-revisions]] |
d19fbc3c BF |
663 | Browsing revisions |
664 | ------------------ | |
665 | ||
5162e697 | 666 | The linkgit:git-log[1] command can show lists of commits. On its |
d19fbc3c BF |
667 | own, it shows all commits reachable from the parent commit; but you |
668 | can also make more specific requests: | |
669 | ||
670 | ------------------------------------------------- | |
671 | $ git log v2.5.. # commits since (not reachable from) v2.5 | |
672 | $ git log test..master # commits reachable from master but not test | |
673 | $ git log master..test # ...reachable from test but not master | |
674 | $ git log master...test # ...reachable from either test or master, | |
675 | # but not both | |
676 | $ git log --since="2 weeks ago" # commits from the last 2 weeks | |
677 | $ git log Makefile # commits which modify Makefile | |
678 | $ git log fs/ # ... which modify any file under fs/ | |
679 | $ git log -S'foo()' # commits which add or remove any file data | |
680 | # matching the string 'foo()' | |
681 | ------------------------------------------------- | |
682 | ||
683 | And of course you can combine all of these; the following finds | |
1249d8ad | 684 | commits since v2.5 which touch the `Makefile` or any file under `fs`: |
d19fbc3c BF |
685 | |
686 | ------------------------------------------------- | |
687 | $ git log v2.5.. Makefile fs/ | |
688 | ------------------------------------------------- | |
689 | ||
690 | You can also ask git log to show patches: | |
691 | ||
692 | ------------------------------------------------- | |
693 | $ git log -p | |
694 | ------------------------------------------------- | |
695 | ||
1249d8ad | 696 | See the `--pretty` option in the linkgit:git-log[1] man page for more |
d19fbc3c BF |
697 | display options. |
698 | ||
699 | Note that git log starts with the most recent commit and works | |
2de9b711 | 700 | backwards through the parents; however, since Git history can contain |
3dff5379 | 701 | multiple independent lines of development, the particular order that |
d19fbc3c BF |
702 | commits are listed in may be somewhat arbitrary. |
703 | ||
e34caace | 704 | [[generating-diffs]] |
d19fbc3c BF |
705 | Generating diffs |
706 | ---------------- | |
707 | ||
708 | You can generate diffs between any two versions using | |
5162e697 | 709 | linkgit:git-diff[1]: |
d19fbc3c BF |
710 | |
711 | ------------------------------------------------- | |
712 | $ git diff master..test | |
713 | ------------------------------------------------- | |
714 | ||
5b98d9bc BF |
715 | That will produce the diff between the tips of the two branches. If |
716 | you'd prefer to find the diff from their common ancestor to test, you | |
717 | can use three dots instead of two: | |
718 | ||
719 | ------------------------------------------------- | |
720 | $ git diff master...test | |
721 | ------------------------------------------------- | |
722 | ||
723 | Sometimes what you want instead is a set of patches; for this you can | |
5162e697 | 724 | use linkgit:git-format-patch[1]: |
d19fbc3c BF |
725 | |
726 | ------------------------------------------------- | |
727 | $ git format-patch master..test | |
728 | ------------------------------------------------- | |
729 | ||
730 | will generate a file with a patch for each commit reachable from test | |
5b98d9bc | 731 | but not from master. |
d19fbc3c | 732 | |
e34caace | 733 | [[viewing-old-file-versions]] |
d19fbc3c BF |
734 | Viewing old file versions |
735 | ------------------------- | |
736 | ||
737 | You can always view an old version of a file by just checking out the | |
738 | correct revision first. But sometimes it is more convenient to be | |
739 | able to view an old version of a single file without checking | |
740 | anything out; this command does that: | |
741 | ||
742 | ------------------------------------------------- | |
743 | $ git show v2.5:fs/locks.c | |
744 | ------------------------------------------------- | |
745 | ||
746 | Before the colon may be anything that names a commit, and after it | |
2de9b711 | 747 | may be any path to a file tracked by Git. |
d19fbc3c | 748 | |
e34caace | 749 | [[history-examples]] |
aec053bb BF |
750 | Examples |
751 | -------- | |
752 | ||
46acd3fa BF |
753 | [[counting-commits-on-a-branch]] |
754 | Counting the number of commits on a branch | |
755 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
756 | ||
1249d8ad TK |
757 | Suppose you want to know how many commits you've made on `mybranch` |
758 | since it diverged from `origin`: | |
46acd3fa BF |
759 | |
760 | ------------------------------------------------- | |
761 | $ git log --pretty=oneline origin..mybranch | wc -l | |
762 | ------------------------------------------------- | |
763 | ||
764 | Alternatively, you may often see this sort of thing done with the | |
a6e5ef7d | 765 | lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's |
46acd3fa BF |
766 | of all the given commits: |
767 | ||
768 | ------------------------------------------------- | |
769 | $ git rev-list origin..mybranch | wc -l | |
770 | ------------------------------------------------- | |
771 | ||
e34caace | 772 | [[checking-for-equal-branches]] |
aec053bb | 773 | Check whether two branches point at the same history |
2f99710c | 774 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
aec053bb BF |
775 | |
776 | Suppose you want to check whether two branches point at the same point | |
777 | in history. | |
778 | ||
779 | ------------------------------------------------- | |
780 | $ git diff origin..master | |
781 | ------------------------------------------------- | |
782 | ||
69f7ad73 BF |
783 | will tell you whether the contents of the project are the same at the |
784 | two branches; in theory, however, it's possible that the same project | |
785 | contents could have been arrived at by two different historical | |
d55ae921 | 786 | routes. You could compare the object names: |
aec053bb BF |
787 | |
788 | ------------------------------------------------- | |
789 | $ git rev-list origin | |
790 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
791 | $ git rev-list master | |
792 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
793 | ------------------------------------------------- | |
794 | ||
1249d8ad | 795 | Or you could recall that the `...` operator selects all commits |
69f7ad73 | 796 | contained reachable from either one reference or the other but not |
ddd2369c | 797 | both; so |
aec053bb BF |
798 | |
799 | ------------------------------------------------- | |
800 | $ git log origin...master | |
801 | ------------------------------------------------- | |
802 | ||
803 | will return no commits when the two branches are equal. | |
804 | ||
e34caace | 805 | [[finding-tagged-descendants]] |
b181d57f BF |
806 | Find first tagged version including a given fix |
807 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
aec053bb | 808 | |
69f7ad73 BF |
809 | Suppose you know that the commit e05db0fd fixed a certain problem. |
810 | You'd like to find the earliest tagged release that contains that | |
811 | fix. | |
812 | ||
813 | Of course, there may be more than one answer--if the history branched | |
814 | after commit e05db0fd, then there could be multiple "earliest" tagged | |
815 | releases. | |
816 | ||
817 | You could just visually inspect the commits since e05db0fd: | |
818 | ||
819 | ------------------------------------------------- | |
820 | $ gitk e05db0fd.. | |
821 | ------------------------------------------------- | |
822 | ||
5162e697 | 823 | Or you can use linkgit:git-name-rev[1], which will give the commit a |
b181d57f BF |
824 | name based on any tag it finds pointing to one of the commit's |
825 | descendants: | |
826 | ||
827 | ------------------------------------------------- | |
04483524 | 828 | $ git name-rev --tags e05db0fd |
b181d57f BF |
829 | e05db0fd tags/v1.5.0-rc1^0~23 |
830 | ------------------------------------------------- | |
831 | ||
5162e697 | 832 | The linkgit:git-describe[1] command does the opposite, naming the |
b181d57f BF |
833 | revision using a tag on which the given commit is based: |
834 | ||
835 | ------------------------------------------------- | |
836 | $ git describe e05db0fd | |
04483524 | 837 | v1.5.0-rc0-260-ge05db0f |
b181d57f BF |
838 | ------------------------------------------------- |
839 | ||
840 | but that may sometimes help you guess which tags might come after the | |
841 | given commit. | |
842 | ||
843 | If you just want to verify whether a given tagged version contains a | |
5162e697 | 844 | given commit, you could use linkgit:git-merge-base[1]: |
b181d57f BF |
845 | |
846 | ------------------------------------------------- | |
847 | $ git merge-base e05db0fd v1.5.0-rc1 | |
848 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
849 | ------------------------------------------------- | |
850 | ||
851 | The merge-base command finds a common ancestor of the given commits, | |
852 | and always returns one or the other in the case where one is a | |
853 | descendant of the other; so the above output shows that e05db0fd | |
854 | actually is an ancestor of v1.5.0-rc1. | |
855 | ||
856 | Alternatively, note that | |
857 | ||
858 | ------------------------------------------------- | |
4a7979ca | 859 | $ git log v1.5.0-rc1..e05db0fd |
b181d57f BF |
860 | ------------------------------------------------- |
861 | ||
4a7979ca | 862 | will produce empty output if and only if v1.5.0-rc1 includes e05db0fd, |
b181d57f | 863 | because it outputs only commits that are not reachable from v1.5.0-rc1. |
aec053bb | 864 | |
5162e697 | 865 | As yet another alternative, the linkgit:git-show-branch[1] command lists |
4a7979ca BF |
866 | the commits reachable from its arguments with a display on the left-hand |
867 | side that indicates which arguments that commit is reachable from. So, | |
868 | you can run something like | |
869 | ||
870 | ------------------------------------------------- | |
871 | $ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2 | |
872 | ! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
873 | available | |
874 | ! [v1.5.0-rc0] GIT v1.5.0 preview | |
875 | ! [v1.5.0-rc1] GIT v1.5.0-rc1 | |
876 | ! [v1.5.0-rc2] GIT v1.5.0-rc2 | |
877 | ... | |
878 | ------------------------------------------------- | |
879 | ||
880 | then search for a line that looks like | |
881 | ||
882 | ------------------------------------------------- | |
883 | + ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
884 | available | |
885 | ------------------------------------------------- | |
886 | ||
887 | Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and | |
888 | from v1.5.0-rc2, but not from v1.5.0-rc0. | |
889 | ||
629d9f78 BF |
890 | [[showing-commits-unique-to-a-branch]] |
891 | Showing commits unique to a given branch | |
892 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
4a7979ca | 893 | |
629d9f78 | 894 | Suppose you would like to see all the commits reachable from the branch |
1249d8ad | 895 | head named `master` but not from any other head in your repository. |
d19fbc3c | 896 | |
629d9f78 | 897 | We can list all the heads in this repository with |
5162e697 | 898 | linkgit:git-show-ref[1]: |
d19fbc3c | 899 | |
629d9f78 BF |
900 | ------------------------------------------------- |
901 | $ git show-ref --heads | |
902 | bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial | |
903 | db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint | |
904 | a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master | |
905 | 24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2 | |
906 | 1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes | |
907 | ------------------------------------------------- | |
d19fbc3c | 908 | |
1249d8ad | 909 | We can get just the branch-head names, and remove `master`, with |
629d9f78 BF |
910 | the help of the standard utilities cut and grep: |
911 | ||
912 | ------------------------------------------------- | |
913 | $ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master' | |
914 | refs/heads/core-tutorial | |
915 | refs/heads/maint | |
916 | refs/heads/tutorial-2 | |
917 | refs/heads/tutorial-fixes | |
918 | ------------------------------------------------- | |
919 | ||
920 | And then we can ask to see all the commits reachable from master | |
921 | but not from these other heads: | |
922 | ||
923 | ------------------------------------------------- | |
924 | $ gitk master --not $( git show-ref --heads | cut -d' ' -f2 | | |
925 | grep -v '^refs/heads/master' ) | |
926 | ------------------------------------------------- | |
927 | ||
928 | Obviously, endless variations are possible; for example, to see all | |
929 | commits reachable from some head but not from any tag in the repository: | |
930 | ||
931 | ------------------------------------------------- | |
c78974f7 | 932 | $ gitk $( git show-ref --heads ) --not $( git show-ref --tags ) |
629d9f78 BF |
933 | ------------------------------------------------- |
934 | ||
9d83e382 | 935 | (See linkgit:gitrevisions[7] for explanations of commit-selecting |
629d9f78 BF |
936 | syntax such as `--not`.) |
937 | ||
82c8bf28 BF |
938 | [[making-a-release]] |
939 | Creating a changelog and tarball for a software release | |
940 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
941 | ||
5162e697 | 942 | The linkgit:git-archive[1] command can create a tar or zip archive from |
82c8bf28 BF |
943 | any version of a project; for example: |
944 | ||
945 | ------------------------------------------------- | |
7ed1690c | 946 | $ git archive -o latest.tar.gz --prefix=project/ HEAD |
82c8bf28 BF |
947 | ------------------------------------------------- |
948 | ||
7ed1690c TK |
949 | will use HEAD to produce a gzipped tar archive in which each filename |
950 | is preceded by `project/`. The output file format is inferred from | |
951 | the output file extension if possible, see linkgit:git-archive[1] for | |
952 | details. | |
953 | ||
1249d8ad | 954 | Versions of Git older than 1.7.7 don't know about the `tar.gz` format, |
7ed1690c TK |
955 | you'll need to use gzip explicitly: |
956 | ||
957 | ------------------------------------------------- | |
958 | $ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz | |
959 | ------------------------------------------------- | |
82c8bf28 BF |
960 | |
961 | If you're releasing a new version of a software project, you may want | |
962 | to simultaneously make a changelog to include in the release | |
963 | announcement. | |
964 | ||
965 | Linus Torvalds, for example, makes new kernel releases by tagging them, | |
966 | then running: | |
967 | ||
968 | ------------------------------------------------- | |
969 | $ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7 | |
970 | ------------------------------------------------- | |
971 | ||
972 | where release-script is a shell script that looks like: | |
973 | ||
974 | ------------------------------------------------- | |
975 | #!/bin/sh | |
976 | stable="$1" | |
977 | last="$2" | |
978 | new="$3" | |
979 | echo "# git tag v$new" | |
980 | echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz" | |
981 | echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz" | |
982 | echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new" | |
983 | echo "git shortlog --no-merges v$new ^v$last > ../ShortLog" | |
984 | echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new" | |
985 | ------------------------------------------------- | |
986 | ||
987 | and then he just cut-and-pastes the output commands after verifying that | |
988 | they look OK. | |
4a7979ca | 989 | |
e1ba4c32 | 990 | [[Finding-commits-With-given-Content]] |
187b0d80 | 991 | Finding commits referencing a file with given content |
d5821de2 | 992 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
187b0d80 BF |
993 | |
994 | Somebody hands you a copy of a file, and asks which commits modified a | |
995 | file such that it contained the given content either before or after the | |
996 | commit. You can find out with this: | |
997 | ||
998 | ------------------------------------------------- | |
477ff5b7 | 999 | $ git log --raw --abbrev=40 --pretty=oneline | |
187b0d80 BF |
1000 | grep -B 1 `git hash-object filename` |
1001 | ------------------------------------------------- | |
1002 | ||
1003 | Figuring out why this works is left as an exercise to the (advanced) | |
5162e697 DM |
1004 | student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and |
1005 | linkgit:git-hash-object[1] man pages may prove helpful. | |
187b0d80 | 1006 | |
aa971cb9 | 1007 | [[Developing-With-git]] |
2de9b711 | 1008 | Developing with Git |
d19fbc3c BF |
1009 | =================== |
1010 | ||
e34caace | 1011 | [[telling-git-your-name]] |
2de9b711 | 1012 | Telling Git your name |
d19fbc3c BF |
1013 | --------------------- |
1014 | ||
632cc3e6 TK |
1015 | Before creating any commits, you should introduce yourself to Git. |
1016 | The easiest way to do so is to use linkgit:git-config[1]: | |
1017 | ||
1018 | ------------------------------------------------ | |
1019 | $ git config --global user.name 'Your Name Comes Here' | |
1020 | $ git config --global user.email 'you@yourdomain.example.com' | |
1021 | ------------------------------------------------ | |
1022 | ||
1023 | Which will add the following to a file named `.gitconfig` in your | |
1024 | home directory: | |
d19fbc3c BF |
1025 | |
1026 | ------------------------------------------------ | |
d19fbc3c BF |
1027 | [user] |
1028 | name = Your Name Comes Here | |
1029 | email = you@yourdomain.example.com | |
d19fbc3c BF |
1030 | ------------------------------------------------ |
1031 | ||
632cc3e6 TK |
1032 | See the "CONFIGURATION FILE" section of linkgit:git-config[1] for |
1033 | details on the configuration file. The file is plain text, so you can | |
1034 | also edit it with your favorite editor. | |
fc90c536 | 1035 | |
d19fbc3c | 1036 | |
e34caace | 1037 | [[creating-a-new-repository]] |
d19fbc3c BF |
1038 | Creating a new repository |
1039 | ------------------------- | |
1040 | ||
1041 | Creating a new repository from scratch is very easy: | |
1042 | ||
1043 | ------------------------------------------------- | |
1044 | $ mkdir project | |
1045 | $ cd project | |
f1d2b477 | 1046 | $ git init |
d19fbc3c BF |
1047 | ------------------------------------------------- |
1048 | ||
1049 | If you have some initial content (say, a tarball): | |
1050 | ||
1051 | ------------------------------------------------- | |
0ddd93b2 | 1052 | $ tar xzvf project.tar.gz |
d19fbc3c | 1053 | $ cd project |
f1d2b477 | 1054 | $ git init |
d19fbc3c BF |
1055 | $ git add . # include everything below ./ in the first commit: |
1056 | $ git commit | |
1057 | ------------------------------------------------- | |
1058 | ||
1059 | [[how-to-make-a-commit]] | |
ae25c67a | 1060 | How to make a commit |
d19fbc3c BF |
1061 | -------------------- |
1062 | ||
1063 | Creating a new commit takes three steps: | |
1064 | ||
1065 | 1. Making some changes to the working directory using your | |
1066 | favorite editor. | |
2de9b711 TA |
1067 | 2. Telling Git about your changes. |
1068 | 3. Creating the commit using the content you told Git about | |
d19fbc3c BF |
1069 | in step 2. |
1070 | ||
1071 | In practice, you can interleave and repeat steps 1 and 2 as many | |
1072 | times as you want: in order to keep track of what you want committed | |
2de9b711 | 1073 | at step 3, Git maintains a snapshot of the tree's contents in a |
d19fbc3c BF |
1074 | special staging area called "the index." |
1075 | ||
01997b4a | 1076 | At the beginning, the content of the index will be identical to |
1249d8ad | 1077 | that of the HEAD. The command `git diff --cached`, which shows |
01997b4a BF |
1078 | the difference between the HEAD and the index, should therefore |
1079 | produce no output at that point. | |
eb6ae7f4 | 1080 | |
d19fbc3c BF |
1081 | Modifying the index is easy: |
1082 | ||
1083 | To update the index with the new contents of a modified file, use | |
1084 | ||
1085 | ------------------------------------------------- | |
1086 | $ git add path/to/file | |
1087 | ------------------------------------------------- | |
1088 | ||
1089 | To add the contents of a new file to the index, use | |
1090 | ||
1091 | ------------------------------------------------- | |
1092 | $ git add path/to/file | |
1093 | ------------------------------------------------- | |
1094 | ||
eb6ae7f4 | 1095 | To remove a file from the index and from the working tree, |
d19fbc3c BF |
1096 | |
1097 | ------------------------------------------------- | |
1098 | $ git rm path/to/file | |
1099 | ------------------------------------------------- | |
1100 | ||
1101 | After each step you can verify that | |
1102 | ||
1103 | ------------------------------------------------- | |
1104 | $ git diff --cached | |
1105 | ------------------------------------------------- | |
1106 | ||
1107 | always shows the difference between the HEAD and the index file--this | |
1108 | is what you'd commit if you created the commit now--and that | |
1109 | ||
1110 | ------------------------------------------------- | |
1111 | $ git diff | |
1112 | ------------------------------------------------- | |
1113 | ||
1114 | shows the difference between the working tree and the index file. | |
1115 | ||
1249d8ad | 1116 | Note that `git add` always adds just the current contents of a file |
d19fbc3c | 1117 | to the index; further changes to the same file will be ignored unless |
6127c086 | 1118 | you run `git add` on the file again. |
d19fbc3c BF |
1119 | |
1120 | When you're ready, just run | |
1121 | ||
1122 | ------------------------------------------------- | |
1123 | $ git commit | |
1124 | ------------------------------------------------- | |
1125 | ||
2de9b711 | 1126 | and Git will prompt you for a commit message and then create the new |
3dff5379 | 1127 | commit. Check to make sure it looks like what you expected with |
d19fbc3c BF |
1128 | |
1129 | ------------------------------------------------- | |
1130 | $ git show | |
1131 | ------------------------------------------------- | |
1132 | ||
1133 | As a special shortcut, | |
a6080a0a | 1134 | |
d19fbc3c BF |
1135 | ------------------------------------------------- |
1136 | $ git commit -a | |
1137 | ------------------------------------------------- | |
1138 | ||
1139 | will update the index with any files that you've modified or removed | |
1140 | and create a commit, all in one step. | |
1141 | ||
1142 | A number of commands are useful for keeping track of what you're | |
1143 | about to commit: | |
1144 | ||
1145 | ------------------------------------------------- | |
1146 | $ git diff --cached # difference between HEAD and the index; what | |
1130845b | 1147 | # would be committed if you ran "commit" now. |
d19fbc3c BF |
1148 | $ git diff # difference between the index file and your |
1149 | # working directory; changes that would not | |
1150 | # be included if you ran "commit" now. | |
c64415e2 BF |
1151 | $ git diff HEAD # difference between HEAD and working tree; what |
1152 | # would be committed if you ran "commit -a" now. | |
d19fbc3c BF |
1153 | $ git status # a brief per-file summary of the above. |
1154 | ------------------------------------------------- | |
1155 | ||
5162e697 | 1156 | You can also use linkgit:git-gui[1] to create commits, view changes in |
407c0c87 BF |
1157 | the index and the working tree files, and individually select diff hunks |
1158 | for inclusion in the index (by right-clicking on the diff hunk and | |
1159 | choosing "Stage Hunk For Commit"). | |
1160 | ||
e34caace | 1161 | [[creating-good-commit-messages]] |
ae25c67a | 1162 | Creating good commit messages |
d19fbc3c BF |
1163 | ----------------------------- |
1164 | ||
1165 | Though not required, it's a good idea to begin the commit message | |
1166 | with a single short (less than 50 character) line summarizing the | |
1167 | change, followed by a blank line and then a more thorough | |
52ffe995 JW |
1168 | description. The text up to the first blank line in a commit |
1169 | message is treated as the commit title, and that title is used | |
2de9b711 | 1170 | throughout Git. For example, linkgit:git-format-patch[1] turns a |
52ffe995 JW |
1171 | commit into email, and it uses the title on the Subject line and the |
1172 | rest of the commit in the body. | |
1173 | ||
d19fbc3c | 1174 | |
2dc53617 JH |
1175 | [[ignoring-files]] |
1176 | Ignoring files | |
1177 | -------------- | |
1178 | ||
2de9b711 | 1179 | A project will often generate files that you do 'not' want to track with Git. |
2dc53617 | 1180 | This typically includes files generated by a build process or temporary |
2de9b711 | 1181 | backup files made by your editor. Of course, 'not' tracking files with Git |
6127c086 | 1182 | is just a matter of 'not' calling `git add` on them. But it quickly becomes |
2dc53617 | 1183 | annoying to have these untracked files lying around; e.g. they make |
dcb11263 CJ |
1184 | `git add .` practically useless, and they keep showing up in the output of |
1185 | `git status`. | |
2dc53617 | 1186 | |
1249d8ad TK |
1187 | You can tell Git to ignore certain files by creating a file called |
1188 | `.gitignore` in the top level of your working directory, with contents | |
1189 | such as: | |
2dc53617 JH |
1190 | |
1191 | ------------------------------------------------- | |
1192 | # Lines starting with '#' are considered comments. | |
464a8a7a | 1193 | # Ignore any file named foo.txt. |
2dc53617 JH |
1194 | foo.txt |
1195 | # Ignore (generated) html files, | |
1196 | *.html | |
1197 | # except foo.html which is maintained by hand. | |
1198 | !foo.html | |
1199 | # Ignore objects and archives. | |
1200 | *.[oa] | |
1201 | ------------------------------------------------- | |
1202 | ||
5162e697 | 1203 | See linkgit:gitignore[5] for a detailed explanation of the syntax. You can |
464a8a7a BF |
1204 | also place .gitignore files in other directories in your working tree, and they |
1205 | will apply to those directories and their subdirectories. The `.gitignore` | |
1206 | files can be added to your repository like any other files (just run `git add | |
1207 | .gitignore` and `git commit`, as usual), which is convenient when the exclude | |
1208 | patterns (such as patterns matching build output files) would also make sense | |
1209 | for other users who clone your repository. | |
1210 | ||
1211 | If you wish the exclude patterns to affect only certain repositories | |
1212 | (instead of every repository for a given project), you may instead put | |
1249d8ad TK |
1213 | them in a file in your repository named `.git/info/exclude`, or in any |
1214 | file specified by the `core.excludesfile` configuration variable. | |
1215 | Some Git commands can also take exclude patterns directly on the | |
1216 | command line. See linkgit:gitignore[5] for the details. | |
2dc53617 | 1217 | |
e34caace | 1218 | [[how-to-merge]] |
ae25c67a | 1219 | How to merge |
d19fbc3c BF |
1220 | ------------ |
1221 | ||
1222 | You can rejoin two diverging branches of development using | |
5162e697 | 1223 | linkgit:git-merge[1]: |
d19fbc3c BF |
1224 | |
1225 | ------------------------------------------------- | |
1226 | $ git merge branchname | |
1227 | ------------------------------------------------- | |
1228 | ||
1249d8ad | 1229 | merges the development in the branch `branchname` into the current |
e63ec003 MM |
1230 | branch. |
1231 | ||
1249d8ad | 1232 | A merge is made by combining the changes made in `branchname` and the |
e63ec003 MM |
1233 | changes made up to the latest commit in your current branch since |
1234 | their histories forked. The work tree is overwritten by the result of | |
1235 | the merge when this combining is done cleanly, or overwritten by a | |
1236 | half-merged results when this combining results in conflicts. | |
1237 | Therefore, if you have uncommitted changes touching the same files as | |
1238 | the ones impacted by the merge, Git will refuse to proceed. Most of | |
1239 | the time, you will want to commit your changes before you can merge, | |
1240 | and if you don't, then linkgit:git-stash[1] can take these changes | |
1241 | away while you're doing the merge, and reapply them afterwards. | |
1242 | ||
6a5d0b0a | 1243 | If the changes are independent enough, Git will automatically complete |
e63ec003 MM |
1244 | the merge and commit the result (or reuse an existing commit in case |
1245 | of <<fast-forwards,fast-forward>>, see below). On the other hand, | |
1246 | if there are conflicts--for example, if the same file is | |
d19fbc3c BF |
1247 | modified in two different ways in the remote branch and the local |
1248 | branch--then you are warned; the output may look something like this: | |
1249 | ||
1250 | ------------------------------------------------- | |
fabbd8f6 BF |
1251 | $ git merge next |
1252 | 100% (4/4) done | |
1253 | Auto-merged file.txt | |
d19fbc3c BF |
1254 | CONFLICT (content): Merge conflict in file.txt |
1255 | Automatic merge failed; fix conflicts and then commit the result. | |
1256 | ------------------------------------------------- | |
1257 | ||
1258 | Conflict markers are left in the problematic files, and after | |
1259 | you resolve the conflicts manually, you can update the index | |
2de9b711 | 1260 | with the contents and run Git commit, as you normally would when |
d19fbc3c BF |
1261 | creating a new file. |
1262 | ||
1263 | If you examine the resulting commit using gitk, you will see that it | |
1264 | has two parents, one pointing to the top of the current branch, and | |
1265 | one to the top of the other branch. | |
1266 | ||
d19fbc3c BF |
1267 | [[resolving-a-merge]] |
1268 | Resolving a merge | |
1269 | ----------------- | |
1270 | ||
2de9b711 | 1271 | When a merge isn't resolved automatically, Git leaves the index and |
d19fbc3c BF |
1272 | the working tree in a special state that gives you all the |
1273 | information you need to help resolve the merge. | |
1274 | ||
1275 | Files with conflicts are marked specially in the index, so until you | |
5162e697 | 1276 | resolve the problem and update the index, linkgit:git-commit[1] will |
ef561ac7 | 1277 | fail: |
d19fbc3c BF |
1278 | |
1279 | ------------------------------------------------- | |
1280 | $ git commit | |
1281 | file.txt: needs merge | |
1282 | ------------------------------------------------- | |
1283 | ||
5162e697 | 1284 | Also, linkgit:git-status[1] will list those files as "unmerged", and the |
ef561ac7 BF |
1285 | files with conflicts will have conflict markers added, like this: |
1286 | ||
1287 | ------------------------------------------------- | |
1288 | <<<<<<< HEAD:file.txt | |
1289 | Hello world | |
1290 | ======= | |
1291 | Goodbye | |
1292 | >>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1293 | ------------------------------------------------- | |
1294 | ||
1295 | All you need to do is edit the files to resolve the conflicts, and then | |
1296 | ||
1297 | ------------------------------------------------- | |
1298 | $ git add file.txt | |
1299 | $ git commit | |
1300 | ------------------------------------------------- | |
1301 | ||
1302 | Note that the commit message will already be filled in for you with | |
1303 | some information about the merge. Normally you can just use this | |
1304 | default message unchanged, but you may add additional commentary of | |
1305 | your own if desired. | |
1306 | ||
2de9b711 | 1307 | The above is all you need to know to resolve a simple merge. But Git |
ef561ac7 BF |
1308 | also provides more information to help resolve conflicts: |
1309 | ||
e34caace | 1310 | [[conflict-resolution]] |
ef561ac7 BF |
1311 | Getting conflict-resolution help during a merge |
1312 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 1313 | |
2de9b711 | 1314 | All of the changes that Git was able to merge automatically are |
5162e697 | 1315 | already added to the index file, so linkgit:git-diff[1] shows only |
ef561ac7 | 1316 | the conflicts. It uses an unusual syntax: |
d19fbc3c BF |
1317 | |
1318 | ------------------------------------------------- | |
1319 | $ git diff | |
1320 | diff --cc file.txt | |
1321 | index 802992c,2b60207..0000000 | |
1322 | --- a/file.txt | |
1323 | +++ b/file.txt | |
1324 | @@@ -1,1 -1,1 +1,5 @@@ | |
1325 | ++<<<<<<< HEAD:file.txt | |
1326 | +Hello world | |
1327 | ++======= | |
1328 | + Goodbye | |
1329 | ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1330 | ------------------------------------------------- | |
1331 | ||
1130845b | 1332 | Recall that the commit which will be committed after we resolve this |
d19fbc3c BF |
1333 | conflict will have two parents instead of the usual one: one parent |
1334 | will be HEAD, the tip of the current branch; the other will be the | |
1335 | tip of the other branch, which is stored temporarily in MERGE_HEAD. | |
1336 | ||
ef561ac7 BF |
1337 | During the merge, the index holds three versions of each file. Each of |
1338 | these three "file stages" represents a different version of the file: | |
1339 | ||
1340 | ------------------------------------------------- | |
1341 | $ git show :1:file.txt # the file in a common ancestor of both branches | |
4209752d JH |
1342 | $ git show :2:file.txt # the version from HEAD. |
1343 | $ git show :3:file.txt # the version from MERGE_HEAD. | |
ef561ac7 BF |
1344 | ------------------------------------------------- |
1345 | ||
4209752d JH |
1346 | When you ask linkgit:git-diff[1] to show the conflicts, it runs a |
1347 | three-way diff between the conflicted merge results in the work tree with | |
1348 | stages 2 and 3 to show only hunks whose contents come from both sides, | |
1349 | mixed (in other words, when a hunk's merge results come only from stage 2, | |
1350 | that part is not conflicting and is not shown. Same for stage 3). | |
ef561ac7 BF |
1351 | |
1352 | The diff above shows the differences between the working-tree version of | |
1353 | file.txt and the stage 2 and stage 3 versions. So instead of preceding | |
1249d8ad | 1354 | each line by a single `+` or `-`, it now uses two columns: the first |
ef561ac7 BF |
1355 | column is used for differences between the first parent and the working |
1356 | directory copy, and the second for differences between the second parent | |
1357 | and the working directory copy. (See the "COMBINED DIFF FORMAT" section | |
5162e697 | 1358 | of linkgit:git-diff-files[1] for a details of the format.) |
ef561ac7 BF |
1359 | |
1360 | After resolving the conflict in the obvious way (but before updating the | |
1361 | index), the diff will look like: | |
d19fbc3c BF |
1362 | |
1363 | ------------------------------------------------- | |
1364 | $ git diff | |
1365 | diff --cc file.txt | |
1366 | index 802992c,2b60207..0000000 | |
1367 | --- a/file.txt | |
1368 | +++ b/file.txt | |
1369 | @@@ -1,1 -1,1 +1,1 @@@ | |
1370 | - Hello world | |
1371 | -Goodbye | |
1372 | ++Goodbye world | |
1373 | ------------------------------------------------- | |
1374 | ||
1375 | This shows that our resolved version deleted "Hello world" from the | |
1376 | first parent, deleted "Goodbye" from the second parent, and added | |
1377 | "Goodbye world", which was previously absent from both. | |
1378 | ||
ef561ac7 BF |
1379 | Some special diff options allow diffing the working directory against |
1380 | any of these stages: | |
1381 | ||
1382 | ------------------------------------------------- | |
1383 | $ git diff -1 file.txt # diff against stage 1 | |
1384 | $ git diff --base file.txt # same as the above | |
1385 | $ git diff -2 file.txt # diff against stage 2 | |
1386 | $ git diff --ours file.txt # same as the above | |
1387 | $ git diff -3 file.txt # diff against stage 3 | |
1388 | $ git diff --theirs file.txt # same as the above. | |
1389 | ------------------------------------------------- | |
1390 | ||
0cafe944 | 1391 | The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help |
ef561ac7 | 1392 | for merges: |
d19fbc3c BF |
1393 | |
1394 | ------------------------------------------------- | |
1395 | $ git log --merge | |
ef561ac7 | 1396 | $ gitk --merge |
d19fbc3c BF |
1397 | ------------------------------------------------- |
1398 | ||
ef561ac7 BF |
1399 | These will display all commits which exist only on HEAD or on |
1400 | MERGE_HEAD, and which touch an unmerged file. | |
d19fbc3c | 1401 | |
5162e697 | 1402 | You may also use linkgit:git-mergetool[1], which lets you merge the |
c7719fbe | 1403 | unmerged files using external tools such as Emacs or kdiff3. |
c64415e2 | 1404 | |
ef561ac7 | 1405 | Each time you resolve the conflicts in a file and update the index: |
d19fbc3c BF |
1406 | |
1407 | ------------------------------------------------- | |
1408 | $ git add file.txt | |
d19fbc3c BF |
1409 | ------------------------------------------------- |
1410 | ||
ef561ac7 | 1411 | the different stages of that file will be "collapsed", after which |
6127c086 | 1412 | `git diff` will (by default) no longer show diffs for that file. |
d19fbc3c BF |
1413 | |
1414 | [[undoing-a-merge]] | |
ae25c67a | 1415 | Undoing a merge |
d19fbc3c BF |
1416 | --------------- |
1417 | ||
1418 | If you get stuck and decide to just give up and throw the whole mess | |
1419 | away, you can always return to the pre-merge state with | |
1420 | ||
1421 | ------------------------------------------------- | |
1422 | $ git reset --hard HEAD | |
1423 | ------------------------------------------------- | |
1424 | ||
1130845b | 1425 | Or, if you've already committed the merge that you want to throw away, |
d19fbc3c BF |
1426 | |
1427 | ------------------------------------------------- | |
1c73bb0e | 1428 | $ git reset --hard ORIG_HEAD |
d19fbc3c BF |
1429 | ------------------------------------------------- |
1430 | ||
1431 | However, this last command can be dangerous in some cases--never | |
1432 | throw away a commit you have already committed if that commit may | |
1433 | itself have been merged into another branch, as doing so may confuse | |
1434 | further merges. | |
1435 | ||
e34caace | 1436 | [[fast-forwards]] |
d19fbc3c BF |
1437 | Fast-forward merges |
1438 | ------------------- | |
1439 | ||
1440 | There is one special case not mentioned above, which is treated | |
1441 | differently. Normally, a merge results in a merge commit, with two | |
1442 | parents, one pointing at each of the two lines of development that | |
1443 | were merged. | |
1444 | ||
59723040 | 1445 | However, if the current branch is a descendant of the other--so every |
2de9b711 | 1446 | commit present in the one is already contained in the other--then Git |
a75d7b54 | 1447 | just performs a "fast-forward"; the head of the current branch is moved |
59723040 BF |
1448 | forward to point at the head of the merged-in branch, without any new |
1449 | commits being created. | |
d19fbc3c | 1450 | |
e34caace | 1451 | [[fixing-mistakes]] |
b684f830 BF |
1452 | Fixing mistakes |
1453 | --------------- | |
1454 | ||
1455 | If you've messed up the working tree, but haven't yet committed your | |
1456 | mistake, you can return the entire working tree to the last committed | |
1457 | state with | |
1458 | ||
1459 | ------------------------------------------------- | |
1460 | $ git reset --hard HEAD | |
1461 | ------------------------------------------------- | |
1462 | ||
1463 | If you make a commit that you later wish you hadn't, there are two | |
1464 | fundamentally different ways to fix the problem: | |
1465 | ||
1466 | 1. You can create a new commit that undoes whatever was done | |
93cbbd71 | 1467 | by the old commit. This is the correct thing if your |
b684f830 BF |
1468 | mistake has already been made public. |
1469 | ||
1470 | 2. You can go back and modify the old commit. You should | |
1471 | never do this if you have already made the history public; | |
2de9b711 | 1472 | Git does not normally expect the "history" of a project to |
b684f830 BF |
1473 | change, and cannot correctly perform repeated merges from |
1474 | a branch that has had its history changed. | |
1475 | ||
e34caace | 1476 | [[reverting-a-commit]] |
b684f830 BF |
1477 | Fixing a mistake with a new commit |
1478 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1479 | ||
1480 | Creating a new commit that reverts an earlier change is very easy; | |
5162e697 | 1481 | just pass the linkgit:git-revert[1] command a reference to the bad |
b684f830 BF |
1482 | commit; for example, to revert the most recent commit: |
1483 | ||
1484 | ------------------------------------------------- | |
1485 | $ git revert HEAD | |
1486 | ------------------------------------------------- | |
1487 | ||
1488 | This will create a new commit which undoes the change in HEAD. You | |
1489 | will be given a chance to edit the commit message for the new commit. | |
1490 | ||
1491 | You can also revert an earlier change, for example, the next-to-last: | |
1492 | ||
1493 | ------------------------------------------------- | |
1494 | $ git revert HEAD^ | |
1495 | ------------------------------------------------- | |
1496 | ||
2de9b711 | 1497 | In this case Git will attempt to undo the old change while leaving |
b684f830 BF |
1498 | intact any changes made since then. If more recent changes overlap |
1499 | with the changes to be reverted, then you will be asked to fix | |
1500 | conflicts manually, just as in the case of <<resolving-a-merge, | |
1501 | resolving a merge>>. | |
1502 | ||
7cb192ea BF |
1503 | [[fixing-a-mistake-by-rewriting-history]] |
1504 | Fixing a mistake by rewriting history | |
b684f830 BF |
1505 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
1506 | ||
1507 | If the problematic commit is the most recent commit, and you have not | |
1508 | yet made that commit public, then you may just | |
6127c086 | 1509 | <<undoing-a-merge,destroy it using `git reset`>>. |
b684f830 BF |
1510 | |
1511 | Alternatively, you | |
1512 | can edit the working directory and update the index to fix your | |
1513 | mistake, just as if you were going to <<how-to-make-a-commit,create a | |
1514 | new commit>>, then run | |
1515 | ||
1516 | ------------------------------------------------- | |
1517 | $ git commit --amend | |
1518 | ------------------------------------------------- | |
1519 | ||
1520 | which will replace the old commit by a new commit incorporating your | |
1521 | changes, giving you a chance to edit the old commit message first. | |
1522 | ||
1523 | Again, you should never do this to a commit that may already have | |
5162e697 | 1524 | been merged into another branch; use linkgit:git-revert[1] instead in |
b684f830 BF |
1525 | that case. |
1526 | ||
7cb192ea | 1527 | It is also possible to replace commits further back in the history, but |
b684f830 BF |
1528 | this is an advanced topic to be left for |
1529 | <<cleaning-up-history,another chapter>>. | |
1530 | ||
e34caace | 1531 | [[checkout-of-path]] |
b684f830 BF |
1532 | Checking out an old version of a file |
1533 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1534 | ||
1535 | In the process of undoing a previous bad change, you may find it | |
1536 | useful to check out an older version of a particular file using | |
6127c086 | 1537 | linkgit:git-checkout[1]. We've used `git checkout` before to switch |
b684f830 BF |
1538 | branches, but it has quite different behavior if it is given a path |
1539 | name: the command | |
1540 | ||
1541 | ------------------------------------------------- | |
1542 | $ git checkout HEAD^ path/to/file | |
1543 | ------------------------------------------------- | |
1544 | ||
1545 | replaces path/to/file by the contents it had in the commit HEAD^, and | |
1546 | also updates the index to match. It does not change branches. | |
1547 | ||
1548 | If you just want to look at an old version of the file, without | |
1549 | modifying the working directory, you can do that with | |
5162e697 | 1550 | linkgit:git-show[1]: |
b684f830 BF |
1551 | |
1552 | ------------------------------------------------- | |
ed4eb0d8 | 1553 | $ git show HEAD^:path/to/file |
b684f830 BF |
1554 | ------------------------------------------------- |
1555 | ||
1556 | which will display the given version of the file. | |
1557 | ||
7a7cc594 JH |
1558 | [[interrupted-work]] |
1559 | Temporarily setting aside work in progress | |
1560 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1561 | ||
1562 | While you are in the middle of working on something complicated, you | |
1563 | find an unrelated but obvious and trivial bug. You would like to fix it | |
5162e697 | 1564 | before continuing. You can use linkgit:git-stash[1] to save the current |
7a7cc594 JH |
1565 | state of your work, and after fixing the bug (or, optionally after doing |
1566 | so on a different branch and then coming back), unstash the | |
1567 | work-in-progress changes. | |
1568 | ||
1569 | ------------------------------------------------ | |
7a85f6ae | 1570 | $ git stash save "work in progress for foo feature" |
7a7cc594 JH |
1571 | ------------------------------------------------ |
1572 | ||
1573 | This command will save your changes away to the `stash`, and | |
1574 | reset your working tree and the index to match the tip of your | |
1575 | current branch. Then you can make your fix as usual. | |
1576 | ||
1577 | ------------------------------------------------ | |
1578 | ... edit and test ... | |
1579 | $ git commit -a -m "blorpl: typofix" | |
1580 | ------------------------------------------------ | |
1581 | ||
1582 | After that, you can go back to what you were working on with | |
7b8988e1 | 1583 | `git stash pop`: |
7a7cc594 JH |
1584 | |
1585 | ------------------------------------------------ | |
7b8988e1 | 1586 | $ git stash pop |
7a7cc594 JH |
1587 | ------------------------------------------------ |
1588 | ||
1589 | ||
e34caace | 1590 | [[ensuring-good-performance]] |
d19fbc3c BF |
1591 | Ensuring good performance |
1592 | ------------------------- | |
1593 | ||
2de9b711 | 1594 | On large repositories, Git depends on compression to keep the history |
901fd180 | 1595 | information from taking up too much space on disk or in memory. Some |
e1ebf212 | 1596 | Git commands may automatically run linkgit:git-gc[1], so you don't |
901fd180 TK |
1597 | have to worry about running it manually. However, compressing a large |
1598 | repository may take a while, so you may want to call `gc` explicitly | |
1599 | to avoid automatic compression kicking in when it is not convenient. | |
d19fbc3c | 1600 | |
e34caace BF |
1601 | |
1602 | [[ensuring-reliability]] | |
11e016a3 BF |
1603 | Ensuring reliability |
1604 | -------------------- | |
1605 | ||
e34caace | 1606 | [[checking-for-corruption]] |
11e016a3 BF |
1607 | Checking the repository for corruption |
1608 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1609 | ||
5162e697 | 1610 | The linkgit:git-fsck[1] command runs a number of self-consistency checks |
1191ee18 | 1611 | on the repository, and reports on any problems. This may take some |
c6a13b2c | 1612 | time. |
21dcb3b7 BF |
1613 | |
1614 | ------------------------------------------------- | |
04e50e94 | 1615 | $ git fsck |
21dcb3b7 BF |
1616 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 |
1617 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1618 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1619 | dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb | |
1620 | dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f | |
1621 | dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e | |
1622 | dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085 | |
1623 | dangling tree b24c2473f1fd3d91352a624795be026d64c8841f | |
1624 | ... | |
1625 | ------------------------------------------------- | |
1626 | ||
c6a13b2c JH |
1627 | You will see informational messages on dangling objects. They are objects |
1628 | that still exist in the repository but are no longer referenced by any of | |
1249d8ad | 1629 | your branches, and can (and will) be removed after a while with `gc`. |
b4ab1980 | 1630 | You can run `git fsck --no-dangling` to suppress these messages, and still |
c6a13b2c | 1631 | view real errors. |
1cdade2c | 1632 | |
e34caace | 1633 | [[recovering-lost-changes]] |
11e016a3 BF |
1634 | Recovering lost changes |
1635 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1636 | ||
e34caace | 1637 | [[reflogs]] |
559e4d7a BF |
1638 | Reflogs |
1639 | ^^^^^^^ | |
1640 | ||
1249d8ad TK |
1641 | Say you modify a branch with <<fixing-mistakes,`git reset --hard`>>, |
1642 | and then realize that the branch was the only reference you had to | |
1643 | that point in history. | |
559e4d7a | 1644 | |
2de9b711 | 1645 | Fortunately, Git also keeps a log, called a "reflog", of all the |
559e4d7a | 1646 | previous values of each branch. So in this case you can still find the |
a6080a0a | 1647 | old history using, for example, |
559e4d7a BF |
1648 | |
1649 | ------------------------------------------------- | |
1650 | $ git log master@{1} | |
1651 | ------------------------------------------------- | |
1652 | ||
e502c2c3 | 1653 | This lists the commits reachable from the previous version of the |
1249d8ad TK |
1654 | `master` branch head. This syntax can be used with any Git command |
1655 | that accepts a commit, not just with `git log`. Some other examples: | |
559e4d7a BF |
1656 | |
1657 | ------------------------------------------------- | |
1658 | $ git show master@{2} # See where the branch pointed 2, | |
1659 | $ git show master@{3} # 3, ... changes ago. | |
1660 | $ gitk master@{yesterday} # See where it pointed yesterday, | |
1661 | $ gitk master@{"1 week ago"} # ... or last week | |
953f3d6f BF |
1662 | $ git log --walk-reflogs master # show reflog entries for master |
1663 | ------------------------------------------------- | |
1664 | ||
1665 | A separate reflog is kept for the HEAD, so | |
1666 | ||
1667 | ------------------------------------------------- | |
1668 | $ git show HEAD@{"1 week ago"} | |
559e4d7a BF |
1669 | ------------------------------------------------- |
1670 | ||
953f3d6f BF |
1671 | will show what HEAD pointed to one week ago, not what the current branch |
1672 | pointed to one week ago. This allows you to see the history of what | |
1673 | you've checked out. | |
1674 | ||
559e4d7a | 1675 | The reflogs are kept by default for 30 days, after which they may be |
5162e697 | 1676 | pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn |
559e4d7a | 1677 | how to control this pruning, and see the "SPECIFYING REVISIONS" |
9d83e382 | 1678 | section of linkgit:gitrevisions[7] for details. |
559e4d7a | 1679 | |
2de9b711 | 1680 | Note that the reflog history is very different from normal Git history. |
559e4d7a BF |
1681 | While normal history is shared by every repository that works on the |
1682 | same project, the reflog history is not shared: it tells you only about | |
1683 | how the branches in your local repository have changed over time. | |
1684 | ||
59723040 | 1685 | [[dangling-object-recovery]] |
559e4d7a BF |
1686 | Examining dangling objects |
1687 | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
1688 | ||
59723040 BF |
1689 | In some situations the reflog may not be able to save you. For example, |
1690 | suppose you delete a branch, then realize you need the history it | |
1691 | contained. The reflog is also deleted; however, if you have not yet | |
1692 | pruned the repository, then you may still be able to find the lost | |
6127c086 | 1693 | commits in the dangling objects that `git fsck` reports. See |
59723040 | 1694 | <<dangling-objects>> for the details. |
559e4d7a BF |
1695 | |
1696 | ------------------------------------------------- | |
1697 | $ git fsck | |
1698 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 | |
1699 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1700 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1701 | ... | |
1702 | ------------------------------------------------- | |
1703 | ||
aacd404e | 1704 | You can examine |
559e4d7a BF |
1705 | one of those dangling commits with, for example, |
1706 | ||
1707 | ------------------------------------------------ | |
1708 | $ gitk 7281251ddd --not --all | |
1709 | ------------------------------------------------ | |
1710 | ||
1711 | which does what it sounds like: it says that you want to see the commit | |
1712 | history that is described by the dangling commit(s), but not the | |
1713 | history that is described by all your existing branches and tags. Thus | |
1714 | you get exactly the history reachable from that commit that is lost. | |
1715 | (And notice that it might not be just one commit: we only report the | |
1716 | "tip of the line" as being dangling, but there might be a whole deep | |
79c96c57 | 1717 | and complex commit history that was dropped.) |
559e4d7a BF |
1718 | |
1719 | If you decide you want the history back, you can always create a new | |
1720 | reference pointing to it, for example, a new branch: | |
1721 | ||
1722 | ------------------------------------------------ | |
a6080a0a | 1723 | $ git branch recovered-branch 7281251ddd |
559e4d7a BF |
1724 | ------------------------------------------------ |
1725 | ||
59723040 BF |
1726 | Other types of dangling objects (blobs and trees) are also possible, and |
1727 | dangling objects can arise in other situations. | |
1728 | ||
11e016a3 | 1729 | |
e34caace | 1730 | [[sharing-development]] |
d19fbc3c | 1731 | Sharing development with others |
b684f830 | 1732 | =============================== |
d19fbc3c | 1733 | |
aa971cb9 | 1734 | [[getting-updates-With-git-pull]] |
6127c086 | 1735 | Getting updates with git pull |
b684f830 | 1736 | ----------------------------- |
d19fbc3c | 1737 | |
e63ec003 | 1738 | After you clone a repository and commit a few changes of your own, you |
d19fbc3c BF |
1739 | may wish to check the original repository for updates and merge them |
1740 | into your own work. | |
1741 | ||
aa971cb9 | 1742 | We have already seen <<Updating-a-repository-With-git-fetch,how to |
0e615b25 | 1743 | keep remote-tracking branches up to date>> with linkgit:git-fetch[1], |
d19fbc3c BF |
1744 | and how to merge two branches. So you can merge in changes from the |
1745 | original repository's master branch with: | |
1746 | ||
1747 | ------------------------------------------------- | |
1748 | $ git fetch | |
1749 | $ git merge origin/master | |
1750 | ------------------------------------------------- | |
1751 | ||
5162e697 | 1752 | However, the linkgit:git-pull[1] command provides a way to do this in |
d19fbc3c BF |
1753 | one step: |
1754 | ||
1755 | ------------------------------------------------- | |
1756 | $ git pull origin master | |
1757 | ------------------------------------------------- | |
1758 | ||
1249d8ad TK |
1759 | In fact, if you have `master` checked out, then this branch has been |
1760 | configured by `git clone` to get changes from the HEAD branch of the | |
66a062a1 | 1761 | origin repository. So often you can |
0eb4f7cd | 1762 | accomplish the above with just a simple |
d19fbc3c BF |
1763 | |
1764 | ------------------------------------------------- | |
1765 | $ git pull | |
1766 | ------------------------------------------------- | |
1767 | ||
66a062a1 MM |
1768 | This command will fetch changes from the remote branches to your |
1769 | remote-tracking branches `origin/*`, and merge the default branch into | |
1770 | the current branch. | |
1771 | ||
29b9a66f MM |
1772 | More generally, a branch that is created from a remote-tracking branch |
1773 | will pull | |
0eb4f7cd | 1774 | by default from that branch. See the descriptions of the |
1249d8ad | 1775 | `branch.<name>.remote` and `branch.<name>.merge` options in |
5162e697 DM |
1776 | linkgit:git-config[1], and the discussion of the `--track` option in |
1777 | linkgit:git-checkout[1], to learn how to control these defaults. | |
d19fbc3c | 1778 | |
1249d8ad | 1779 | In addition to saving you keystrokes, `git pull` also helps you by |
d19fbc3c BF |
1780 | producing a default commit message documenting the branch and |
1781 | repository that you pulled from. | |
1782 | ||
1783 | (But note that no such commit will be created in the case of a | |
a75d7b54 | 1784 | <<fast-forwards,fast-forward>>; instead, your branch will just be |
79c96c57 | 1785 | updated to point to the latest commit from the upstream branch.) |
d19fbc3c | 1786 | |
1249d8ad | 1787 | The `git pull` command can also be given `.` as the "remote" repository, |
1191ee18 | 1788 | in which case it just merges in a branch from the current repository; so |
4c63ff45 BF |
1789 | the commands |
1790 | ||
1791 | ------------------------------------------------- | |
1792 | $ git pull . branch | |
1793 | $ git merge branch | |
1794 | ------------------------------------------------- | |
1795 | ||
1796 | are roughly equivalent. The former is actually very commonly used. | |
1797 | ||
e34caace | 1798 | [[submitting-patches]] |
d19fbc3c | 1799 | Submitting patches to a project |
b684f830 | 1800 | ------------------------------- |
d19fbc3c BF |
1801 | |
1802 | If you just have a few changes, the simplest way to submit them may | |
1803 | just be to send them as patches in email: | |
1804 | ||
5162e697 | 1805 | First, use linkgit:git-format-patch[1]; for example: |
d19fbc3c BF |
1806 | |
1807 | ------------------------------------------------- | |
eb6ae7f4 | 1808 | $ git format-patch origin |
d19fbc3c BF |
1809 | ------------------------------------------------- |
1810 | ||
1811 | will produce a numbered series of files in the current directory, one | |
1249d8ad | 1812 | for each patch in the current branch but not in `origin/HEAD`. |
d19fbc3c | 1813 | |
d84cef18 PO |
1814 | `git format-patch` can include an initial "cover letter". You can insert |
1815 | commentary on individual patches after the three dash line which | |
1816 | `format-patch` places after the commit message but before the patch | |
1817 | itself. If you use `git notes` to track your cover letter material, | |
1818 | `git format-patch --notes` will include the commit's notes in a similar | |
1819 | manner. | |
1820 | ||
d19fbc3c BF |
1821 | You can then import these into your mail client and send them by |
1822 | hand. However, if you have a lot to send at once, you may prefer to | |
5162e697 | 1823 | use the linkgit:git-send-email[1] script to automate the process. |
d19fbc3c BF |
1824 | Consult the mailing list for your project first to determine how they |
1825 | prefer such patches be handled. | |
1826 | ||
e34caace | 1827 | [[importing-patches]] |
d19fbc3c | 1828 | Importing patches to a project |
b684f830 | 1829 | ------------------------------ |
d19fbc3c | 1830 | |
5162e697 | 1831 | Git also provides a tool called linkgit:git-am[1] (am stands for |
d19fbc3c BF |
1832 | "apply mailbox"), for importing such an emailed series of patches. |
1833 | Just save all of the patch-containing messages, in order, into a | |
1249d8ad | 1834 | single mailbox file, say `patches.mbox`, then run |
d19fbc3c BF |
1835 | |
1836 | ------------------------------------------------- | |
eb6ae7f4 | 1837 | $ git am -3 patches.mbox |
d19fbc3c BF |
1838 | ------------------------------------------------- |
1839 | ||
1840 | Git will apply each patch in order; if any conflicts are found, it | |
1841 | will stop, and you can fix the conflicts as described in | |
1249d8ad | 1842 | "<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells |
2de9b711 | 1843 | Git to perform a merge; if you would prefer it just to abort and |
01997b4a BF |
1844 | leave your tree and index untouched, you may omit that option.) |
1845 | ||
1846 | Once the index is updated with the results of the conflict | |
1847 | resolution, instead of creating a new commit, just run | |
d19fbc3c BF |
1848 | |
1849 | ------------------------------------------------- | |
8ceb6fbd | 1850 | $ git am --continue |
d19fbc3c BF |
1851 | ------------------------------------------------- |
1852 | ||
2de9b711 | 1853 | and Git will create the commit for you and continue applying the |
d19fbc3c BF |
1854 | remaining patches from the mailbox. |
1855 | ||
1856 | The final result will be a series of commits, one for each patch in | |
1857 | the original mailbox, with authorship and commit log message each | |
1858 | taken from the message containing each patch. | |
1859 | ||
eda69449 | 1860 | [[public-repositories]] |
2de9b711 | 1861 | Public Git repositories |
eda69449 | 1862 | ----------------------- |
d19fbc3c | 1863 | |
6e30fb0c DK |
1864 | Another way to submit changes to a project is to tell the maintainer |
1865 | of that project to pull the changes from your repository using | |
aa971cb9 | 1866 | linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull, |
6127c086 | 1867 | Getting updates with `git pull`>>" we described this as a way to get |
6e30fb0c DK |
1868 | updates from the "main" repository, but it works just as well in the |
1869 | other direction. | |
d19fbc3c | 1870 | |
eda69449 BF |
1871 | If you and the maintainer both have accounts on the same machine, then |
1872 | you can just pull changes from each other's repositories directly; | |
11d51533 | 1873 | commands that accept repository URLs as arguments will also accept a |
eda69449 | 1874 | local directory name: |
d19fbc3c BF |
1875 | |
1876 | ------------------------------------------------- | |
1877 | $ git clone /path/to/repository | |
1878 | $ git pull /path/to/other/repository | |
1879 | ------------------------------------------------- | |
1880 | ||
c9016158 | 1881 | or an ssh URL: |
11d51533 BF |
1882 | |
1883 | ------------------------------------------------- | |
1884 | $ git clone ssh://yourhost/~you/repository | |
1885 | ------------------------------------------------- | |
1886 | ||
1887 | For projects with few developers, or for synchronizing a few private | |
1888 | repositories, this may be all you need. | |
1889 | ||
eda69449 BF |
1890 | However, the more common way to do this is to maintain a separate public |
1891 | repository (usually on a different host) for others to pull changes | |
1892 | from. This is usually more convenient, and allows you to cleanly | |
1893 | separate private work in progress from publicly visible work. | |
d19fbc3c BF |
1894 | |
1895 | You will continue to do your day-to-day work in your personal | |
1896 | repository, but periodically "push" changes from your personal | |
1897 | repository into your public repository, allowing other developers to | |
1898 | pull from that repository. So the flow of changes, in a situation | |
1899 | where there is one other developer with a public repository, looks | |
1900 | like this: | |
1901 | ||
1902 | you push | |
1903 | your personal repo ------------------> your public repo | |
a6080a0a | 1904 | ^ | |
d19fbc3c BF |
1905 | | | |
1906 | | you pull | they pull | |
1907 | | | | |
1908 | | | | |
1909 | | they push V | |
1910 | their public repo <------------------- their repo | |
1911 | ||
11d51533 BF |
1912 | We explain how to do this in the following sections. |
1913 | ||
eda69449 BF |
1914 | [[setting-up-a-public-repository]] |
1915 | Setting up a public repository | |
1916 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1917 | ||
1249d8ad | 1918 | Assume your personal repository is in the directory `~/proj`. We |
6127c086 | 1919 | first create a new clone of the repository and tell `git daemon` that it |
eda69449 | 1920 | is meant to be public: |
d19fbc3c BF |
1921 | |
1922 | ------------------------------------------------- | |
52c80037 | 1923 | $ git clone --bare ~/proj proj.git |
eda69449 | 1924 | $ touch proj.git/git-daemon-export-ok |
d19fbc3c BF |
1925 | ------------------------------------------------- |
1926 | ||
52c80037 | 1927 | The resulting directory proj.git contains a "bare" git repository--it is |
1249d8ad | 1928 | just the contents of the `.git` directory, without any files checked out |
eda69449 | 1929 | around it. |
d19fbc3c | 1930 | |
1249d8ad | 1931 | Next, copy `proj.git` to the server where you plan to host the |
d19fbc3c BF |
1932 | public repository. You can use scp, rsync, or whatever is most |
1933 | convenient. | |
1934 | ||
eda69449 | 1935 | [[exporting-via-git]] |
2de9b711 | 1936 | Exporting a Git repository via the Git protocol |
eda69449 BF |
1937 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
1938 | ||
1939 | This is the preferred method. | |
1940 | ||
1941 | If someone else administers the server, they should tell you what | |
1249d8ad TK |
1942 | directory to put the repository in, and what `git://` URL it will |
1943 | appear at. You can then skip to the section | |
d19fbc3c BF |
1944 | "<<pushing-changes-to-a-public-repository,Pushing changes to a public |
1945 | repository>>", below. | |
1946 | ||
5162e697 | 1947 | Otherwise, all you need to do is start linkgit:git-daemon[1]; it will |
eda69449 | 1948 | listen on port 9418. By default, it will allow access to any directory |
2de9b711 | 1949 | that looks like a Git directory and contains the magic file |
6127c086 | 1950 | git-daemon-export-ok. Passing some directory paths as `git daemon` |
eda69449 BF |
1951 | arguments will further restrict the exports to those paths. |
1952 | ||
6127c086 | 1953 | You can also run `git daemon` as an inetd service; see the |
5162e697 | 1954 | linkgit:git-daemon[1] man page for details. (See especially the |
eda69449 | 1955 | examples section.) |
d19fbc3c BF |
1956 | |
1957 | [[exporting-via-http]] | |
de3f2c7b | 1958 | Exporting a git repository via HTTP |
eda69449 | 1959 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c | 1960 | |
2de9b711 | 1961 | The Git protocol gives better performance and reliability, but on a |
de3f2c7b | 1962 | host with a web server set up, HTTP exports may be simpler to set up. |
d19fbc3c | 1963 | |
2de9b711 | 1964 | All you need to do is place the newly created bare Git repository in |
d19fbc3c BF |
1965 | a directory that is exported by the web server, and make some |
1966 | adjustments to give web clients some extra information they need: | |
1967 | ||
1968 | ------------------------------------------------- | |
1969 | $ mv proj.git /home/you/public_html/proj.git | |
1970 | $ cd proj.git | |
c64415e2 | 1971 | $ git --bare update-server-info |
7dce9918 | 1972 | $ mv hooks/post-update.sample hooks/post-update |
d19fbc3c BF |
1973 | ------------------------------------------------- |
1974 | ||
1975 | (For an explanation of the last two lines, see | |
6998e4db | 1976 | linkgit:git-update-server-info[1] and linkgit:githooks[5].) |
d19fbc3c | 1977 | |
1249d8ad | 1978 | Advertise the URL of `proj.git`. Anybody else should then be able to |
c9016158 | 1979 | clone or pull from that URL, for example with a command line like: |
d19fbc3c BF |
1980 | |
1981 | ------------------------------------------------- | |
1982 | $ git clone http://yourserver.com/~you/proj.git | |
1983 | ------------------------------------------------- | |
1984 | ||
1985 | (See also | |
1986 | link:howto/setup-git-server-over-http.txt[setup-git-server-over-http] | |
1987 | for a slightly more sophisticated setup using WebDAV which also | |
de3f2c7b | 1988 | allows pushing over HTTP.) |
d19fbc3c | 1989 | |
d19fbc3c BF |
1990 | [[pushing-changes-to-a-public-repository]] |
1991 | Pushing changes to a public repository | |
eda69449 | 1992 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c | 1993 | |
eda69449 | 1994 | Note that the two techniques outlined above (exporting via |
d19fbc3c BF |
1995 | <<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other |
1996 | maintainers to fetch your latest changes, but they do not allow write | |
1997 | access, which you will need to update the public repository with the | |
1998 | latest changes created in your private repository. | |
1999 | ||
5162e697 | 2000 | The simplest way to do this is using linkgit:git-push[1] and ssh; to |
1249d8ad TK |
2001 | update the remote branch named `master` with the latest state of your |
2002 | branch named `master`, run | |
d19fbc3c BF |
2003 | |
2004 | ------------------------------------------------- | |
2005 | $ git push ssh://yourserver.com/~you/proj.git master:master | |
2006 | ------------------------------------------------- | |
2007 | ||
2008 | or just | |
2009 | ||
2010 | ------------------------------------------------- | |
2011 | $ git push ssh://yourserver.com/~you/proj.git master | |
2012 | ------------------------------------------------- | |
2013 | ||
6127c086 | 2014 | As with `git fetch`, `git push` will complain if this does not result in a |
a75d7b54 | 2015 | <<fast-forwards,fast-forward>>; see the following section for details on |
81eb417a | 2016 | handling this case. |
d19fbc3c | 2017 | |
1249d8ad | 2018 | Note that the target of a `push` is normally a |
11d51533 | 2019 | <<def_bare_repository,bare>> repository. You can also push to a |
d9be2485 TK |
2020 | repository that has a checked-out working tree, but a push to update the |
2021 | currently checked-out branch is denied by default to prevent confusion. | |
50995edd | 2022 | See the description of the receive.denyCurrentBranch option |
d9be2485 | 2023 | in linkgit:git-config[1] for details. |
11d51533 | 2024 | |
6127c086 | 2025 | As with `git fetch`, you may also set up configuration options to |
e9b49083 TK |
2026 | save typing; so, for example: |
2027 | ||
2028 | ------------------------------------------------- | |
2029 | $ git remote add public-repo ssh://yourserver.com/~you/proj.git | |
2030 | ------------------------------------------------- | |
2031 | ||
2032 | adds the following to `.git/config`: | |
d19fbc3c BF |
2033 | |
2034 | ------------------------------------------------- | |
d19fbc3c | 2035 | [remote "public-repo"] |
e9b49083 TK |
2036 | url = yourserver.com:proj.git |
2037 | fetch = +refs/heads/*:refs/remotes/example/* | |
d19fbc3c BF |
2038 | ------------------------------------------------- |
2039 | ||
e9b49083 | 2040 | which lets you do the same push with just |
d19fbc3c BF |
2041 | |
2042 | ------------------------------------------------- | |
2043 | $ git push public-repo master | |
2044 | ------------------------------------------------- | |
2045 | ||
1249d8ad TK |
2046 | See the explanations of the `remote.<name>.url`, |
2047 | `branch.<name>.remote`, and `remote.<name>.push` options in | |
2048 | linkgit:git-config[1] for details. | |
d19fbc3c | 2049 | |
81eb417a BF |
2050 | [[forcing-push]] |
2051 | What to do when a push fails | |
2052 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
2053 | ||
a75d7b54 | 2054 | If a push would not result in a <<fast-forwards,fast-forward>> of the |
81eb417a BF |
2055 | remote branch, then it will fail with an error like: |
2056 | ||
2057 | ------------------------------------------------- | |
2058 | error: remote 'refs/heads/master' is not an ancestor of | |
2059 | local 'refs/heads/master'. | |
2060 | Maybe you are not up-to-date and need to pull first? | |
2061 | error: failed to push to 'ssh://yourserver.com/~you/proj.git' | |
2062 | ------------------------------------------------- | |
2063 | ||
2064 | This can happen, for example, if you: | |
2065 | ||
6127c086 FC |
2066 | - use `git reset --hard` to remove already-published commits, or |
2067 | - use `git commit --amend` to replace already-published commits | |
7cb192ea | 2068 | (as in <<fixing-a-mistake-by-rewriting-history>>), or |
6127c086 | 2069 | - use `git rebase` to rebase any already-published commits (as |
81eb417a BF |
2070 | in <<using-git-rebase>>). |
2071 | ||
6127c086 | 2072 | You may force `git push` to perform the update anyway by preceding the |
81eb417a BF |
2073 | branch name with a plus sign: |
2074 | ||
2075 | ------------------------------------------------- | |
2076 | $ git push ssh://yourserver.com/~you/proj.git +master | |
2077 | ------------------------------------------------- | |
2078 | ||
d1471e06 TK |
2079 | Note the addition of the `+` sign. Alternatively, you can use the |
2080 | `-f` flag to force the remote update, as in: | |
2081 | ||
2082 | ------------------------------------------------- | |
2083 | $ git push -f ssh://yourserver.com/~you/proj.git master | |
2084 | ------------------------------------------------- | |
2085 | ||
81eb417a | 2086 | Normally whenever a branch head in a public repository is modified, it |
9e5d87d4 | 2087 | is modified to point to a descendant of the commit that it pointed to |
81eb417a | 2088 | before. By forcing a push in this situation, you break that convention. |
aa971cb9 | 2089 | (See <<problems-With-rewriting-history>>.) |
81eb417a BF |
2090 | |
2091 | Nevertheless, this is a common practice for people that need a simple | |
2092 | way to publish a work-in-progress patch series, and it is an acceptable | |
2093 | compromise as long as you warn other developers that this is how you | |
2094 | intend to manage the branch. | |
2095 | ||
2096 | It's also possible for a push to fail in this way when other people have | |
2097 | the right to push to the same repository. In that case, the correct | |
843c81dc EH |
2098 | solution is to retry the push after first updating your work: either by a |
2099 | pull, or by a fetch followed by a rebase; see the | |
81eb417a | 2100 | <<setting-up-a-shared-repository,next section>> and |
6998e4db | 2101 | linkgit:gitcvs-migration[7] for more. |
81eb417a | 2102 | |
e34caace | 2103 | [[setting-up-a-shared-repository]] |
d19fbc3c | 2104 | Setting up a shared repository |
eda69449 | 2105 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c BF |
2106 | |
2107 | Another way to collaborate is by using a model similar to that | |
2108 | commonly used in CVS, where several developers with special rights | |
2109 | all push to and pull from a single shared repository. See | |
6998e4db | 2110 | linkgit:gitcvs-migration[7] for instructions on how to |
d19fbc3c BF |
2111 | set this up. |
2112 | ||
2de9b711 | 2113 | However, while there is nothing wrong with Git's support for shared |
8fae2225 | 2114 | repositories, this mode of operation is not generally recommended, |
2de9b711 | 2115 | simply because the mode of collaboration that Git supports--by |
8fae2225 BF |
2116 | exchanging patches and pulling from public repositories--has so many |
2117 | advantages over the central shared repository: | |
2118 | ||
2119 | - Git's ability to quickly import and merge patches allows a | |
2120 | single maintainer to process incoming changes even at very | |
6127c086 | 2121 | high rates. And when that becomes too much, `git pull` provides |
8fae2225 BF |
2122 | an easy way for that maintainer to delegate this job to other |
2123 | maintainers while still allowing optional review of incoming | |
2124 | changes. | |
2125 | - Since every developer's repository has the same complete copy | |
2126 | of the project history, no repository is special, and it is | |
2127 | trivial for another developer to take over maintenance of a | |
2128 | project, either by mutual agreement, or because a maintainer | |
2129 | becomes unresponsive or difficult to work with. | |
2130 | - The lack of a central group of "committers" means there is | |
2131 | less need for formal decisions about who is "in" and who is | |
2132 | "out". | |
2133 | ||
e34caace | 2134 | [[setting-up-gitweb]] |
eda69449 BF |
2135 | Allowing web browsing of a repository |
2136 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 2137 | |
a8cd1402 | 2138 | The gitweb cgi script provides users an easy way to browse your |
2de9b711 TA |
2139 | project's files and history without having to install Git; see the file |
2140 | gitweb/INSTALL in the Git source tree for instructions on setting it up. | |
d19fbc3c | 2141 | |
e34caace | 2142 | [[sharing-development-examples]] |
b684f830 BF |
2143 | Examples |
2144 | -------- | |
d19fbc3c | 2145 | |
9e2163ea BF |
2146 | [[maintaining-topic-branches]] |
2147 | Maintaining topic branches for a Linux subsystem maintainer | |
2148 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
2149 | ||
2de9b711 | 2150 | This describes how Tony Luck uses Git in his role as maintainer of the |
9e2163ea BF |
2151 | IA64 architecture for the Linux kernel. |
2152 | ||
2153 | He uses two public branches: | |
2154 | ||
2155 | - A "test" tree into which patches are initially placed so that they | |
2156 | can get some exposure when integrated with other ongoing development. | |
2157 | This tree is available to Andrew for pulling into -mm whenever he | |
2158 | wants. | |
2159 | ||
2160 | - A "release" tree into which tested patches are moved for final sanity | |
2161 | checking, and as a vehicle to send them upstream to Linus (by sending | |
2162 | him a "please pull" request.) | |
2163 | ||
2164 | He also uses a set of temporary branches ("topic branches"), each | |
2165 | containing a logical grouping of patches. | |
2166 | ||
2167 | To set this up, first create your work tree by cloning Linus's public | |
2168 | tree: | |
2169 | ||
2170 | ------------------------------------------------- | |
283efb01 | 2171 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work |
9e2163ea BF |
2172 | $ cd work |
2173 | ------------------------------------------------- | |
2174 | ||
29b9a66f | 2175 | Linus's tree will be stored in the remote-tracking branch named origin/master, |
5162e697 DM |
2176 | and can be updated using linkgit:git-fetch[1]; you can track other |
2177 | public trees using linkgit:git-remote[1] to set up a "remote" and | |
2178 | linkgit:git-fetch[1] to keep them up-to-date; see | |
6e30fb0c | 2179 | <<repositories-and-branches>>. |
9e2163ea BF |
2180 | |
2181 | Now create the branches in which you are going to work; these start out | |
2182 | at the current tip of origin/master branch, and should be set up (using | |
1249d8ad | 2183 | the `--track` option to linkgit:git-branch[1]) to merge changes in from |
9e2163ea BF |
2184 | Linus by default. |
2185 | ||
2186 | ------------------------------------------------- | |
2187 | $ git branch --track test origin/master | |
2188 | $ git branch --track release origin/master | |
2189 | ------------------------------------------------- | |
2190 | ||
5162e697 | 2191 | These can be easily kept up to date using linkgit:git-pull[1]. |
9e2163ea BF |
2192 | |
2193 | ------------------------------------------------- | |
2194 | $ git checkout test && git pull | |
2195 | $ git checkout release && git pull | |
2196 | ------------------------------------------------- | |
2197 | ||
2198 | Important note! If you have any local changes in these branches, then | |
2199 | this merge will create a commit object in the history (with no local | |
2de9b711 | 2200 | changes Git will simply do a "fast-forward" merge). Many people dislike |
9e2163ea | 2201 | the "noise" that this creates in the Linux history, so you should avoid |
1249d8ad | 2202 | doing this capriciously in the `release` branch, as these noisy commits |
9e2163ea BF |
2203 | will become part of the permanent history when you ask Linus to pull |
2204 | from the release branch. | |
2205 | ||
5162e697 | 2206 | A few configuration variables (see linkgit:git-config[1]) can |
9e2163ea BF |
2207 | make it easy to push both branches to your public tree. (See |
2208 | <<setting-up-a-public-repository>>.) | |
2209 | ||
2210 | ------------------------------------------------- | |
2211 | $ cat >> .git/config <<EOF | |
2212 | [remote "mytree"] | |
283efb01 | 2213 | url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git |
9e2163ea BF |
2214 | push = release |
2215 | push = test | |
2216 | EOF | |
2217 | ------------------------------------------------- | |
2218 | ||
2219 | Then you can push both the test and release trees using | |
5162e697 | 2220 | linkgit:git-push[1]: |
9e2163ea BF |
2221 | |
2222 | ------------------------------------------------- | |
2223 | $ git push mytree | |
2224 | ------------------------------------------------- | |
2225 | ||
2226 | or push just one of the test and release branches using: | |
2227 | ||
2228 | ------------------------------------------------- | |
2229 | $ git push mytree test | |
2230 | ------------------------------------------------- | |
2231 | ||
2232 | or | |
2233 | ||
2234 | ------------------------------------------------- | |
2235 | $ git push mytree release | |
2236 | ------------------------------------------------- | |
2237 | ||
2238 | Now to apply some patches from the community. Think of a short | |
2239 | snappy name for a branch to hold this patch (or related group of | |
352953a5 TL |
2240 | patches), and create a new branch from a recent stable tag of |
2241 | Linus's branch. Picking a stable base for your branch will: | |
2242 | 1) help you: by avoiding inclusion of unrelated and perhaps lightly | |
2243 | tested changes | |
1249d8ad | 2244 | 2) help future bug hunters that use `git bisect` to find problems |
9e2163ea BF |
2245 | |
2246 | ------------------------------------------------- | |
352953a5 | 2247 | $ git checkout -b speed-up-spinlocks v2.6.35 |
9e2163ea BF |
2248 | ------------------------------------------------- |
2249 | ||
2250 | Now you apply the patch(es), run some tests, and commit the change(s). If | |
2251 | the patch is a multi-part series, then you should apply each as a separate | |
2252 | commit to this branch. | |
2253 | ||
2254 | ------------------------------------------------- | |
2255 | $ ... patch ... test ... commit [ ... patch ... test ... commit ]* | |
2256 | ------------------------------------------------- | |
2257 | ||
2258 | When you are happy with the state of this change, you can pull it into the | |
2259 | "test" branch in preparation to make it public: | |
2260 | ||
2261 | ------------------------------------------------- | |
2262 | $ git checkout test && git pull . speed-up-spinlocks | |
2263 | ------------------------------------------------- | |
2264 | ||
2265 | It is unlikely that you would have any conflicts here ... but you might if you | |
2266 | spent a while on this step and had also pulled new versions from upstream. | |
2267 | ||
2268 | Some time later when enough time has passed and testing done, you can pull the | |
1249d8ad | 2269 | same branch into the `release` tree ready to go upstream. This is where you |
9e2163ea | 2270 | see the value of keeping each patch (or patch series) in its own branch. It |
1249d8ad | 2271 | means that the patches can be moved into the `release` tree in any order. |
9e2163ea BF |
2272 | |
2273 | ------------------------------------------------- | |
2274 | $ git checkout release && git pull . speed-up-spinlocks | |
2275 | ------------------------------------------------- | |
2276 | ||
2277 | After a while, you will have a number of branches, and despite the | |
2278 | well chosen names you picked for each of them, you may forget what | |
2279 | they are for, or what status they are in. To get a reminder of what | |
2280 | changes are in a specific branch, use: | |
2281 | ||
2282 | ------------------------------------------------- | |
467c0197 | 2283 | $ git log linux..branchname | git shortlog |
9e2163ea BF |
2284 | ------------------------------------------------- |
2285 | ||
06ada152 | 2286 | To see whether it has already been merged into the test or release branches, |
9e2163ea BF |
2287 | use: |
2288 | ||
2289 | ------------------------------------------------- | |
2290 | $ git log test..branchname | |
2291 | ------------------------------------------------- | |
2292 | ||
2293 | or | |
2294 | ||
2295 | ------------------------------------------------- | |
2296 | $ git log release..branchname | |
2297 | ------------------------------------------------- | |
2298 | ||
06ada152 | 2299 | (If this branch has not yet been merged, you will see some log entries. |
9e2163ea BF |
2300 | If it has been merged, then there will be no output.) |
2301 | ||
2302 | Once a patch completes the great cycle (moving from test to release, | |
2303 | then pulled by Linus, and finally coming back into your local | |
1249d8ad | 2304 | `origin/master` branch), the branch for this change is no longer needed. |
9e2163ea BF |
2305 | You detect this when the output from: |
2306 | ||
2307 | ------------------------------------------------- | |
2308 | $ git log origin..branchname | |
2309 | ------------------------------------------------- | |
2310 | ||
2311 | is empty. At this point the branch can be deleted: | |
2312 | ||
2313 | ------------------------------------------------- | |
2314 | $ git branch -d branchname | |
2315 | ------------------------------------------------- | |
2316 | ||
2317 | Some changes are so trivial that it is not necessary to create a separate | |
2318 | branch and then merge into each of the test and release branches. For | |
1249d8ad TK |
2319 | these changes, just apply directly to the `release` branch, and then |
2320 | merge that into the `test` branch. | |
9e2163ea | 2321 | |
ae6ef554 TK |
2322 | After pushing your work to `mytree`, you can use |
2323 | linkgit:git-request-pull[1] to prepare a "please pull" request message | |
2324 | to send to Linus: | |
9e2163ea BF |
2325 | |
2326 | ------------------------------------------------- | |
ae6ef554 TK |
2327 | $ git push mytree |
2328 | $ git request-pull origin mytree release | |
9e2163ea BF |
2329 | ------------------------------------------------- |
2330 | ||
2331 | Here are some of the scripts that simplify all this even further. | |
2332 | ||
2333 | ------------------------------------------------- | |
2334 | ==== update script ==== | |
48a8c26c | 2335 | # Update a branch in my Git tree. If the branch to be updated |
9e2163ea BF |
2336 | # is origin, then pull from kernel.org. Otherwise merge |
2337 | # origin/master branch into test|release branch | |
2338 | ||
2339 | case "$1" in | |
2340 | test|release) | |
2341 | git checkout $1 && git pull . origin | |
2342 | ;; | |
2343 | origin) | |
fc74ecc1 | 2344 | before=$(git rev-parse refs/remotes/origin/master) |
9e2163ea | 2345 | git fetch origin |
fc74ecc1 | 2346 | after=$(git rev-parse refs/remotes/origin/master) |
9e2163ea BF |
2347 | if [ $before != $after ] |
2348 | then | |
2349 | git log $before..$after | git shortlog | |
2350 | fi | |
2351 | ;; | |
2352 | *) | |
1a2ba8b9 | 2353 | echo "usage: $0 origin|test|release" 1>&2 |
9e2163ea BF |
2354 | exit 1 |
2355 | ;; | |
2356 | esac | |
2357 | ------------------------------------------------- | |
2358 | ||
2359 | ------------------------------------------------- | |
2360 | ==== merge script ==== | |
2361 | # Merge a branch into either the test or release branch | |
2362 | ||
2363 | pname=$0 | |
2364 | ||
2365 | usage() | |
2366 | { | |
1a2ba8b9 | 2367 | echo "usage: $pname branch test|release" 1>&2 |
9e2163ea BF |
2368 | exit 1 |
2369 | } | |
2370 | ||
fc74ecc1 | 2371 | git show-ref -q --verify -- refs/heads/"$1" || { |
9e2163ea BF |
2372 | echo "Can't see branch <$1>" 1>&2 |
2373 | usage | |
fc74ecc1 | 2374 | } |
9e2163ea BF |
2375 | |
2376 | case "$2" in | |
2377 | test|release) | |
2378 | if [ $(git log $2..$1 | wc -c) -eq 0 ] | |
2379 | then | |
2380 | echo $1 already merged into $2 1>&2 | |
2381 | exit 1 | |
2382 | fi | |
2383 | git checkout $2 && git pull . $1 | |
2384 | ;; | |
2385 | *) | |
2386 | usage | |
2387 | ;; | |
2388 | esac | |
2389 | ------------------------------------------------- | |
2390 | ||
2391 | ------------------------------------------------- | |
2392 | ==== status script ==== | |
48a8c26c | 2393 | # report on status of my ia64 Git tree |
9e2163ea BF |
2394 | |
2395 | gb=$(tput setab 2) | |
2396 | rb=$(tput setab 1) | |
2397 | restore=$(tput setab 9) | |
2398 | ||
2399 | if [ `git rev-list test..release | wc -c` -gt 0 ] | |
2400 | then | |
2401 | echo $rb Warning: commits in release that are not in test $restore | |
2402 | git log test..release | |
2403 | fi | |
2404 | ||
fc74ecc1 | 2405 | for branch in `git show-ref --heads | sed 's|^.*/||'` |
9e2163ea BF |
2406 | do |
2407 | if [ $branch = test -o $branch = release ] | |
2408 | then | |
2409 | continue | |
2410 | fi | |
2411 | ||
2412 | echo -n $gb ======= $branch ====== $restore " " | |
2413 | status= | |
2414 | for ref in test release origin/master | |
2415 | do | |
2416 | if [ `git rev-list $ref..$branch | wc -c` -gt 0 ] | |
2417 | then | |
2418 | status=$status${ref:0:1} | |
2419 | fi | |
2420 | done | |
2421 | case $status in | |
2422 | trl) | |
2423 | echo $rb Need to pull into test $restore | |
2424 | ;; | |
2425 | rl) | |
2426 | echo "In test" | |
2427 | ;; | |
2428 | l) | |
2429 | echo "Waiting for linus" | |
2430 | ;; | |
2431 | "") | |
2432 | echo $rb All done $restore | |
2433 | ;; | |
2434 | *) | |
2435 | echo $rb "<$status>" $restore | |
2436 | ;; | |
2437 | esac | |
2438 | git log origin/master..$branch | git shortlog | |
2439 | done | |
2440 | ------------------------------------------------- | |
d19fbc3c | 2441 | |
d19fbc3c | 2442 | |
d19fbc3c | 2443 | [[cleaning-up-history]] |
4c63ff45 BF |
2444 | Rewriting history and maintaining patch series |
2445 | ============================================== | |
2446 | ||
2447 | Normally commits are only added to a project, never taken away or | |
2448 | replaced. Git is designed with this assumption, and violating it will | |
2de9b711 | 2449 | cause Git's merge machinery (for example) to do the wrong thing. |
4c63ff45 BF |
2450 | |
2451 | However, there is a situation in which it can be useful to violate this | |
2452 | assumption. | |
2453 | ||
e34caace | 2454 | [[patch-series]] |
4c63ff45 BF |
2455 | Creating the perfect patch series |
2456 | --------------------------------- | |
2457 | ||
2458 | Suppose you are a contributor to a large project, and you want to add a | |
2459 | complicated feature, and to present it to the other developers in a way | |
2460 | that makes it easy for them to read your changes, verify that they are | |
2461 | correct, and understand why you made each change. | |
2462 | ||
b181d57f | 2463 | If you present all of your changes as a single patch (or commit), they |
79c96c57 | 2464 | may find that it is too much to digest all at once. |
4c63ff45 BF |
2465 | |
2466 | If you present them with the entire history of your work, complete with | |
2467 | mistakes, corrections, and dead ends, they may be overwhelmed. | |
2468 | ||
2469 | So the ideal is usually to produce a series of patches such that: | |
2470 | ||
2471 | 1. Each patch can be applied in order. | |
2472 | ||
2473 | 2. Each patch includes a single logical change, together with a | |
2474 | message explaining the change. | |
2475 | ||
2476 | 3. No patch introduces a regression: after applying any initial | |
2477 | part of the series, the resulting project still compiles and | |
2478 | works, and has no bugs that it didn't have before. | |
2479 | ||
2480 | 4. The complete series produces the same end result as your own | |
2481 | (probably much messier!) development process did. | |
2482 | ||
b181d57f BF |
2483 | We will introduce some tools that can help you do this, explain how to |
2484 | use them, and then explain some of the problems that can arise because | |
2485 | you are rewriting history. | |
4c63ff45 | 2486 | |
e34caace | 2487 | [[using-git-rebase]] |
6127c086 | 2488 | Keeping a patch series up to date using git rebase |
4c63ff45 BF |
2489 | -------------------------------------------------- |
2490 | ||
1249d8ad TK |
2491 | Suppose that you create a branch `mywork` on a remote-tracking branch |
2492 | `origin`, and create some commits on top of it: | |
4c63ff45 BF |
2493 | |
2494 | ------------------------------------------------- | |
2495 | $ git checkout -b mywork origin | |
2496 | $ vi file.txt | |
2497 | $ git commit | |
2498 | $ vi otherfile.txt | |
2499 | $ git commit | |
2500 | ... | |
2501 | ------------------------------------------------- | |
2502 | ||
2503 | You have performed no merges into mywork, so it is just a simple linear | |
1249d8ad | 2504 | sequence of patches on top of `origin`: |
4c63ff45 | 2505 | |
1dc71a91 | 2506 | ................................................ |
fa8347b8 | 2507 | o--o--O <-- origin |
4c63ff45 | 2508 | \ |
fa8347b8 | 2509 | a--b--c <-- mywork |
1dc71a91 | 2510 | ................................................ |
4c63ff45 BF |
2511 | |
2512 | Some more interesting work has been done in the upstream project, and | |
1249d8ad | 2513 | `origin` has advanced: |
4c63ff45 | 2514 | |
1dc71a91 | 2515 | ................................................ |
4c63ff45 BF |
2516 | o--o--O--o--o--o <-- origin |
2517 | \ | |
2518 | a--b--c <-- mywork | |
1dc71a91 | 2519 | ................................................ |
4c63ff45 | 2520 | |
1249d8ad | 2521 | At this point, you could use `pull` to merge your changes back in; |
4c63ff45 BF |
2522 | the result would create a new merge commit, like this: |
2523 | ||
1dc71a91 | 2524 | ................................................ |
4c63ff45 BF |
2525 | o--o--O--o--o--o <-- origin |
2526 | \ \ | |
2527 | a--b--c--m <-- mywork | |
1dc71a91 | 2528 | ................................................ |
a6080a0a | 2529 | |
4c63ff45 BF |
2530 | However, if you prefer to keep the history in mywork a simple series of |
2531 | commits without any merges, you may instead choose to use | |
5162e697 | 2532 | linkgit:git-rebase[1]: |
4c63ff45 BF |
2533 | |
2534 | ------------------------------------------------- | |
2535 | $ git checkout mywork | |
2536 | $ git rebase origin | |
2537 | ------------------------------------------------- | |
2538 | ||
b181d57f | 2539 | This will remove each of your commits from mywork, temporarily saving |
1249d8ad | 2540 | them as patches (in a directory named `.git/rebase-apply`), update mywork to |
b181d57f BF |
2541 | point at the latest version of origin, then apply each of the saved |
2542 | patches to the new mywork. The result will look like: | |
4c63ff45 BF |
2543 | |
2544 | ||
1dc71a91 | 2545 | ................................................ |
4c63ff45 BF |
2546 | o--o--O--o--o--o <-- origin |
2547 | \ | |
2548 | a'--b'--c' <-- mywork | |
1dc71a91 | 2549 | ................................................ |
4c63ff45 | 2550 | |
b181d57f | 2551 | In the process, it may discover conflicts. In that case it will stop |
6127c086 | 2552 | and allow you to fix the conflicts; after fixing conflicts, use `git add` |
7a7d4ef6 | 2553 | to update the index with those contents, and then, instead of |
6127c086 | 2554 | running `git commit`, just run |
4c63ff45 BF |
2555 | |
2556 | ------------------------------------------------- | |
2557 | $ git rebase --continue | |
2558 | ------------------------------------------------- | |
2559 | ||
2de9b711 | 2560 | and Git will continue applying the rest of the patches. |
4c63ff45 | 2561 | |
b6cbca38 | 2562 | At any point you may use the `--abort` option to abort this process and |
4c63ff45 BF |
2563 | return mywork to the state it had before you started the rebase: |
2564 | ||
2565 | ------------------------------------------------- | |
2566 | $ git rebase --abort | |
2567 | ------------------------------------------------- | |
2568 | ||
6c26bf4d TK |
2569 | If you need to reorder or edit a number of commits in a branch, it may |
2570 | be easier to use `git rebase -i`, which allows you to reorder and | |
2571 | squash commits, as well as marking them for individual editing during | |
2572 | the rebase. See <<interactive-rebase>> for details, and | |
2573 | <<reordering-patch-series>> for alternatives. | |
2574 | ||
7cb192ea BF |
2575 | [[rewriting-one-commit]] |
2576 | Rewriting a single commit | |
365aa199 BF |
2577 | ------------------------- |
2578 | ||
7cb192ea | 2579 | We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the |
365aa199 BF |
2580 | most recent commit using |
2581 | ||
2582 | ------------------------------------------------- | |
2583 | $ git commit --amend | |
2584 | ------------------------------------------------- | |
2585 | ||
2586 | which will replace the old commit by a new commit incorporating your | |
2587 | changes, giving you a chance to edit the old commit message first. | |
6c26bf4d TK |
2588 | This is useful for fixing typos in your last commit, or for adjusting |
2589 | the patch contents of a poorly staged commit. | |
365aa199 | 2590 | |
6c26bf4d TK |
2591 | If you need to amend commits from deeper in your history, you can |
2592 | use <<interactive-rebase,interactive rebase's `edit` instruction>>. | |
365aa199 | 2593 | |
6c26bf4d TK |
2594 | [[reordering-patch-series]] |
2595 | Reordering or selecting from a patch series | |
2596 | ------------------------------------------- | |
365aa199 | 2597 | |
6c26bf4d TK |
2598 | Sometimes you want to edit a commit deeper in your history. One |
2599 | approach is to use `git format-patch` to create a series of patches | |
2600 | and then reset the state to before the patches: | |
365aa199 BF |
2601 | |
2602 | ------------------------------------------------- | |
6c26bf4d TK |
2603 | $ git format-patch origin |
2604 | $ git reset --hard origin | |
365aa199 BF |
2605 | ------------------------------------------------- |
2606 | ||
6c26bf4d TK |
2607 | Then modify, reorder, or eliminate patches as needed before applying |
2608 | them again with linkgit:git-am[1]: | |
365aa199 BF |
2609 | |
2610 | ------------------------------------------------- | |
6c26bf4d | 2611 | $ git am *.patch |
365aa199 BF |
2612 | ------------------------------------------------- |
2613 | ||
6c26bf4d TK |
2614 | [[interactive-rebase]] |
2615 | Using interactive rebases | |
2616 | ------------------------- | |
365aa199 | 2617 | |
6c26bf4d TK |
2618 | You can also edit a patch series with an interactive rebase. This is |
2619 | the same as <<reordering-patch-series,reordering a patch series using | |
2620 | `format-patch`>>, so use whichever interface you like best. | |
4c63ff45 | 2621 | |
6c26bf4d TK |
2622 | Rebase your current HEAD on the last commit you want to retain as-is. |
2623 | For example, if you want to reorder the last 5 commits, use: | |
b181d57f BF |
2624 | |
2625 | ------------------------------------------------- | |
6c26bf4d | 2626 | $ git rebase -i HEAD~5 |
b181d57f BF |
2627 | ------------------------------------------------- |
2628 | ||
6c26bf4d TK |
2629 | This will open your editor with a list of steps to be taken to perform |
2630 | your rebase. | |
4c63ff45 | 2631 | |
b181d57f | 2632 | ------------------------------------------------- |
6c26bf4d TK |
2633 | pick deadbee The oneline of this commit |
2634 | pick fa1afe1 The oneline of the next commit | |
2635 | ... | |
4c63ff45 | 2636 | |
6c26bf4d TK |
2637 | # Rebase c0ffeee..deadbee onto c0ffeee |
2638 | # | |
2639 | # Commands: | |
2640 | # p, pick = use commit | |
2641 | # r, reword = use commit, but edit the commit message | |
2642 | # e, edit = use commit, but stop for amending | |
2643 | # s, squash = use commit, but meld into previous commit | |
2644 | # f, fixup = like "squash", but discard this commit's log message | |
2645 | # x, exec = run command (the rest of the line) using shell | |
2646 | # | |
2647 | # These lines can be re-ordered; they are executed from top to bottom. | |
2648 | # | |
2649 | # If you remove a line here THAT COMMIT WILL BE LOST. | |
2650 | # | |
2651 | # However, if you remove everything, the rebase will be aborted. | |
2652 | # | |
2653 | # Note that empty commits are commented out | |
2654 | ------------------------------------------------- | |
2655 | ||
2656 | As explained in the comments, you can reorder commits, squash them | |
2657 | together, edit commit messages, etc. by editing the list. Once you | |
2658 | are satisfied, save the list and close your editor, and the rebase | |
2659 | will begin. | |
2660 | ||
2661 | The rebase will stop where `pick` has been replaced with `edit` or | |
2662 | when a step in the list fails to mechanically resolve conflicts and | |
2663 | needs your help. When you are done editing and/or resolving conflicts | |
2664 | you can continue with `git rebase --continue`. If you decide that | |
2665 | things are getting too hairy, you can always bail out with `git rebase | |
2666 | --abort`. Even after the rebase is complete, you can still recover | |
2667 | the original branch by using the <<reflogs,reflog>>. | |
2668 | ||
2669 | For a more detailed discussion of the procedure and additional tips, | |
2670 | see the "INTERACTIVE MODE" section of linkgit:git-rebase[1]. | |
4c63ff45 | 2671 | |
e34caace | 2672 | [[patch-series-tools]] |
4c63ff45 BF |
2673 | Other tools |
2674 | ----------- | |
2675 | ||
73a1d050 | 2676 | There are numerous other tools, such as StGit, which exist for the |
79c96c57 | 2677 | purpose of maintaining a patch series. These are outside of the scope of |
b181d57f | 2678 | this manual. |
4c63ff45 | 2679 | |
aa971cb9 | 2680 | [[problems-With-rewriting-history]] |
4c63ff45 BF |
2681 | Problems with rewriting history |
2682 | ------------------------------- | |
2683 | ||
b181d57f BF |
2684 | The primary problem with rewriting the history of a branch has to do |
2685 | with merging. Suppose somebody fetches your branch and merges it into | |
2686 | their branch, with a result something like this: | |
2687 | ||
1dc71a91 | 2688 | ................................................ |
b181d57f BF |
2689 | o--o--O--o--o--o <-- origin |
2690 | \ \ | |
2691 | t--t--t--m <-- their branch: | |
1dc71a91 | 2692 | ................................................ |
b181d57f BF |
2693 | |
2694 | Then suppose you modify the last three commits: | |
2695 | ||
1dc71a91 | 2696 | ................................................ |
b181d57f BF |
2697 | o--o--o <-- new head of origin |
2698 | / | |
2699 | o--o--O--o--o--o <-- old head of origin | |
1dc71a91 | 2700 | ................................................ |
b181d57f BF |
2701 | |
2702 | If we examined all this history together in one repository, it will | |
2703 | look like: | |
2704 | ||
1dc71a91 | 2705 | ................................................ |
b181d57f BF |
2706 | o--o--o <-- new head of origin |
2707 | / | |
2708 | o--o--O--o--o--o <-- old head of origin | |
2709 | \ \ | |
2710 | t--t--t--m <-- their branch: | |
1dc71a91 | 2711 | ................................................ |
b181d57f BF |
2712 | |
2713 | Git has no way of knowing that the new head is an updated version of | |
2714 | the old head; it treats this situation exactly the same as it would if | |
2715 | two developers had independently done the work on the old and new heads | |
2716 | in parallel. At this point, if someone attempts to merge the new head | |
2de9b711 | 2717 | in to their branch, Git will attempt to merge together the two (old and |
b181d57f BF |
2718 | new) lines of development, instead of trying to replace the old by the |
2719 | new. The results are likely to be unexpected. | |
2720 | ||
2721 | You may still choose to publish branches whose history is rewritten, | |
2722 | and it may be useful for others to be able to fetch those branches in | |
2723 | order to examine or test them, but they should not attempt to pull such | |
2724 | branches into their own work. | |
2725 | ||
2726 | For true distributed development that supports proper merging, | |
2727 | published branches should never be rewritten. | |
2728 | ||
3fb00282 SP |
2729 | [[bisect-merges]] |
2730 | Why bisecting merge commits can be harder than bisecting linear history | |
2731 | ----------------------------------------------------------------------- | |
2732 | ||
5162e697 | 2733 | The linkgit:git-bisect[1] command correctly handles history that |
3fb00282 SP |
2734 | includes merge commits. However, when the commit that it finds is a |
2735 | merge commit, the user may need to work harder than usual to figure out | |
2736 | why that commit introduced a problem. | |
2737 | ||
2738 | Imagine this history: | |
2739 | ||
2740 | ................................................ | |
2741 | ---Z---o---X---...---o---A---C---D | |
2742 | \ / | |
2743 | o---o---Y---...---o---B | |
2744 | ................................................ | |
2745 | ||
2746 | Suppose that on the upper line of development, the meaning of one | |
2747 | of the functions that exists at Z is changed at commit X. The | |
2748 | commits from Z leading to A change both the function's | |
2749 | implementation and all calling sites that exist at Z, as well | |
2750 | as new calling sites they add, to be consistent. There is no | |
2751 | bug at A. | |
2752 | ||
2753 | Suppose that in the meantime on the lower line of development somebody | |
2754 | adds a new calling site for that function at commit Y. The | |
2755 | commits from Z leading to B all assume the old semantics of that | |
2756 | function and the callers and the callee are consistent with each | |
2757 | other. There is no bug at B, either. | |
2758 | ||
2759 | Suppose further that the two development lines merge cleanly at C, | |
2760 | so no conflict resolution is required. | |
2761 | ||
2762 | Nevertheless, the code at C is broken, because the callers added | |
2763 | on the lower line of development have not been converted to the new | |
2764 | semantics introduced on the upper line of development. So if all | |
2765 | you know is that D is bad, that Z is good, and that | |
5162e697 | 2766 | linkgit:git-bisect[1] identifies C as the culprit, how will you |
3fb00282 SP |
2767 | figure out that the problem is due to this change in semantics? |
2768 | ||
6127c086 | 2769 | When the result of a `git bisect` is a non-merge commit, you should |
3fb00282 SP |
2770 | normally be able to discover the problem by examining just that commit. |
2771 | Developers can make this easy by breaking their changes into small | |
2772 | self-contained commits. That won't help in the case above, however, | |
2773 | because the problem isn't obvious from examination of any single | |
2774 | commit; instead, a global view of the development is required. To | |
2775 | make matters worse, the change in semantics in the problematic | |
2776 | function may be just one small part of the changes in the upper | |
2777 | line of development. | |
2778 | ||
2779 | On the other hand, if instead of merging at C you had rebased the | |
2780 | history between Z to B on top of A, you would have gotten this | |
2781 | linear history: | |
2782 | ||
2783 | ................................................................ | |
2784 | ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D* | |
2785 | ................................................................ | |
2786 | ||
2787 | Bisecting between Z and D* would hit a single culprit commit Y*, | |
2788 | and understanding why Y* was broken would probably be easier. | |
2789 | ||
2de9b711 | 2790 | Partly for this reason, many experienced Git users, even when |
3fb00282 SP |
2791 | working on an otherwise merge-heavy project, keep the history |
2792 | linear by rebasing against the latest upstream version before | |
2793 | publishing. | |
2794 | ||
e34caace | 2795 | [[advanced-branch-management]] |
b181d57f BF |
2796 | Advanced branch management |
2797 | ========================== | |
4c63ff45 | 2798 | |
e34caace | 2799 | [[fetching-individual-branches]] |
b181d57f BF |
2800 | Fetching individual branches |
2801 | ---------------------------- | |
2802 | ||
5162e697 | 2803 | Instead of using linkgit:git-remote[1], you can also choose just |
b181d57f BF |
2804 | to update one branch at a time, and to store it locally under an |
2805 | arbitrary name: | |
2806 | ||
2807 | ------------------------------------------------- | |
2808 | $ git fetch origin todo:my-todo-work | |
2809 | ------------------------------------------------- | |
2810 | ||
1249d8ad | 2811 | The first argument, `origin`, just tells Git to fetch from the |
2de9b711 | 2812 | repository you originally cloned from. The second argument tells Git |
1249d8ad TK |
2813 | to fetch the branch named `todo` from the remote repository, and to |
2814 | store it locally under the name `refs/heads/my-todo-work`. | |
b181d57f BF |
2815 | |
2816 | You can also fetch branches from other repositories; so | |
2817 | ||
2818 | ------------------------------------------------- | |
2819 | $ git fetch git://example.com/proj.git master:example-master | |
2820 | ------------------------------------------------- | |
2821 | ||
1249d8ad TK |
2822 | will create a new branch named `example-master` and store in it the |
2823 | branch named `master` from the repository at the given URL. If you | |
b181d57f | 2824 | already have a branch named example-master, it will attempt to |
59723040 BF |
2825 | <<fast-forwards,fast-forward>> to the commit given by example.com's |
2826 | master branch. In more detail: | |
b181d57f | 2827 | |
59723040 BF |
2828 | [[fetch-fast-forwards]] |
2829 | git fetch and fast-forwards | |
2830 | --------------------------- | |
b181d57f | 2831 | |
1249d8ad | 2832 | In the previous example, when updating an existing branch, `git fetch` |
7a7d4ef6 | 2833 | checks to make sure that the most recent commit on the remote |
b181d57f BF |
2834 | branch is a descendant of the most recent commit on your copy of the |
2835 | branch before updating your copy of the branch to point at the new | |
a75d7b54 | 2836 | commit. Git calls this process a <<fast-forwards,fast-forward>>. |
b181d57f | 2837 | |
a75d7b54 | 2838 | A fast-forward looks something like this: |
b181d57f | 2839 | |
1dc71a91 | 2840 | ................................................ |
b181d57f BF |
2841 | o--o--o--o <-- old head of the branch |
2842 | \ | |
2843 | o--o--o <-- new head of the branch | |
1dc71a91 | 2844 | ................................................ |
b181d57f BF |
2845 | |
2846 | ||
2847 | In some cases it is possible that the new head will *not* actually be | |
2848 | a descendant of the old head. For example, the developer may have | |
2849 | realized she made a serious mistake, and decided to backtrack, | |
2850 | resulting in a situation like: | |
2851 | ||
1dc71a91 | 2852 | ................................................ |
b181d57f BF |
2853 | o--o--o--o--a--b <-- old head of the branch |
2854 | \ | |
2855 | o--o--o <-- new head of the branch | |
1dc71a91 | 2856 | ................................................ |
b181d57f | 2857 | |
1249d8ad | 2858 | In this case, `git fetch` will fail, and print out a warning. |
b181d57f | 2859 | |
2de9b711 | 2860 | In that case, you can still force Git to update to the new head, as |
b181d57f | 2861 | described in the following section. However, note that in the |
1249d8ad | 2862 | situation above this may mean losing the commits labeled `a` and `b`, |
b181d57f BF |
2863 | unless you've already created a reference of your own pointing to |
2864 | them. | |
2865 | ||
e34caace | 2866 | [[forcing-fetch]] |
6127c086 | 2867 | Forcing git fetch to do non-fast-forward updates |
b181d57f BF |
2868 | ------------------------------------------------ |
2869 | ||
2870 | If git fetch fails because the new head of a branch is not a | |
2871 | descendant of the old head, you may force the update with: | |
2872 | ||
2873 | ------------------------------------------------- | |
2874 | $ git fetch git://example.com/proj.git +master:refs/remotes/example/master | |
2875 | ------------------------------------------------- | |
2876 | ||
1249d8ad | 2877 | Note the addition of the `+` sign. Alternatively, you can use the `-f` |
c64415e2 BF |
2878 | flag to force updates of all the fetched branches, as in: |
2879 | ||
2880 | ------------------------------------------------- | |
2881 | $ git fetch -f origin | |
2882 | ------------------------------------------------- | |
2883 | ||
2884 | Be aware that commits that the old version of example/master pointed at | |
2885 | may be lost, as we saw in the previous section. | |
b181d57f | 2886 | |
e34caace | 2887 | [[remote-branch-configuration]] |
29b9a66f MM |
2888 | Configuring remote-tracking branches |
2889 | ------------------------------------ | |
b181d57f | 2890 | |
1249d8ad | 2891 | We saw above that `origin` is just a shortcut to refer to the |
79c96c57 | 2892 | repository that you originally cloned from. This information is |
2de9b711 | 2893 | stored in Git configuration variables, which you can see using |
5162e697 | 2894 | linkgit:git-config[1]: |
b181d57f BF |
2895 | |
2896 | ------------------------------------------------- | |
9d13bda3 | 2897 | $ git config -l |
b181d57f BF |
2898 | core.repositoryformatversion=0 |
2899 | core.filemode=true | |
2900 | core.logallrefupdates=true | |
2901 | remote.origin.url=git://git.kernel.org/pub/scm/git/git.git | |
2902 | remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* | |
2903 | branch.master.remote=origin | |
2904 | branch.master.merge=refs/heads/master | |
2905 | ------------------------------------------------- | |
2906 | ||
2907 | If there are other repositories that you also use frequently, you can | |
2908 | create similar configuration options to save typing; for example, | |
b181d57f BF |
2909 | |
2910 | ------------------------------------------------- | |
47adb8ac | 2911 | $ git remote add example git://example.com/proj.git |
b181d57f BF |
2912 | ------------------------------------------------- |
2913 | ||
47adb8ac | 2914 | adds the following to `.git/config`: |
b181d57f BF |
2915 | |
2916 | ------------------------------------------------- | |
47adb8ac TK |
2917 | [remote "example"] |
2918 | url = git://example.com/proj.git | |
2919 | fetch = +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2920 | ------------------------------------------------- |
2921 | ||
47adb8ac TK |
2922 | Also note that the above configuration can be performed by directly |
2923 | editing the file `.git/config` instead of using linkgit:git-remote[1]. | |
b181d57f | 2924 | |
47adb8ac TK |
2925 | After configuring the remote, the following three commands will do the |
2926 | same thing: | |
b181d57f BF |
2927 | |
2928 | ------------------------------------------------- | |
47adb8ac TK |
2929 | $ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/* |
2930 | $ git fetch example +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2931 | $ git fetch example |
2932 | ------------------------------------------------- | |
2933 | ||
5162e697 | 2934 | See linkgit:git-config[1] for more details on the configuration |
47adb8ac TK |
2935 | options mentioned above and linkgit:git-fetch[1] for more details on |
2936 | the refspec syntax. | |
d19fbc3c | 2937 | |
d19fbc3c | 2938 | |
036f8199 BF |
2939 | [[git-concepts]] |
2940 | Git concepts | |
2941 | ============ | |
d19fbc3c | 2942 | |
036f8199 BF |
2943 | Git is built on a small number of simple but powerful ideas. While it |
2944 | is possible to get things done without understanding them, you will find | |
2de9b711 | 2945 | Git much more intuitive if you do. |
036f8199 BF |
2946 | |
2947 | We start with the most important, the <<def_object_database,object | |
2948 | database>> and the <<def_index,index>>. | |
b181d57f | 2949 | |
e34caace | 2950 | [[the-object-database]] |
b181d57f BF |
2951 | The Object Database |
2952 | ------------------- | |
2953 | ||
1bbf1c79 BF |
2954 | |
2955 | We already saw in <<understanding-commits>> that all commits are stored | |
2956 | under a 40-digit "object name". In fact, all the information needed to | |
2957 | represent the history of a project is stored in objects with such names. | |
a6e5ef7d FC |
2958 | In each case the name is calculated by taking the SHA-1 hash of the |
2959 | contents of the object. The SHA-1 hash is a cryptographic hash function. | |
1bbf1c79 BF |
2960 | What that means to us is that it is impossible to find two different |
2961 | objects with the same name. This has a number of advantages; among | |
2962 | others: | |
2963 | ||
2964 | - Git can quickly determine whether two objects are identical or not, | |
2965 | just by comparing names. | |
06ada152 | 2966 | - Since object names are computed the same way in every repository, the |
1bbf1c79 BF |
2967 | same content stored in two repositories will always be stored under |
2968 | the same name. | |
2969 | - Git can detect errors when it reads an object, by checking that the | |
a6e5ef7d | 2970 | object's name is still the SHA-1 hash of its contents. |
1bbf1c79 BF |
2971 | |
2972 | (See <<object-details>> for the details of the object formatting and | |
a6e5ef7d | 2973 | SHA-1 calculation.) |
1bbf1c79 BF |
2974 | |
2975 | There are four different types of objects: "blob", "tree", "commit", and | |
2976 | "tag". | |
2977 | ||
2978 | - A <<def_blob_object,"blob" object>> is used to store file data. | |
843c81dc | 2979 | - A <<def_tree_object,"tree" object>> ties one or more |
1bbf1c79 BF |
2980 | "blob" objects into a directory structure. In addition, a tree object |
2981 | can refer to other tree objects, thus creating a directory hierarchy. | |
2982 | - A <<def_commit_object,"commit" object>> ties such directory hierarchies | |
2ef8ac1b | 2983 | together into a <<def_DAG,directed acyclic graph>> of revisions--each |
1bbf1c79 BF |
2984 | commit contains the object name of exactly one tree designating the |
2985 | directory hierarchy at the time of the commit. In addition, a commit | |
2986 | refers to "parent" commit objects that describe the history of how we | |
2987 | arrived at that directory hierarchy. | |
2988 | - A <<def_tag_object,"tag" object>> symbolically identifies and can be | |
2989 | used to sign other objects. It contains the object name and type of | |
2990 | another object, a symbolic name (of course!) and, optionally, a | |
2991 | signature. | |
b181d57f | 2992 | |
b181d57f BF |
2993 | The object types in some more detail: |
2994 | ||
513d419c BF |
2995 | [[commit-object]] |
2996 | Commit Object | |
2997 | ~~~~~~~~~~~~~ | |
b181d57f | 2998 | |
1bbf1c79 | 2999 | The "commit" object links a physical state of a tree with a description |
1249d8ad | 3000 | of how we got there and why. Use the `--pretty=raw` option to |
5162e697 | 3001 | linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite |
1bbf1c79 BF |
3002 | commit: |
3003 | ||
3004 | ------------------------------------------------ | |
3005 | $ git show -s --pretty=raw 2be7fcb476 | |
3006 | commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4 | |
3007 | tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf | |
3008 | parent 257a84d9d02e90447b149af58b271c19405edb6a | |
3009 | author Dave Watson <dwatson@mimvista.com> 1187576872 -0400 | |
3010 | committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700 | |
3011 | ||
3012 | Fix misspelling of 'suppress' in docs | |
3013 | ||
3014 | Signed-off-by: Junio C Hamano <gitster@pobox.com> | |
3015 | ------------------------------------------------ | |
3016 | ||
3017 | As you can see, a commit is defined by: | |
3018 | ||
a6e5ef7d | 3019 | - a tree: The SHA-1 name of a tree object (as defined below), representing |
1bbf1c79 | 3020 | the contents of a directory at a certain point in time. |
edfbbf7e | 3021 | - parent(s): The SHA-1 name(s) of some number of commits which represent the |
9e5d87d4 | 3022 | immediately previous step(s) in the history of the project. The |
1bbf1c79 BF |
3023 | example above has one parent; merge commits may have more than |
3024 | one. A commit with no parents is called a "root" commit, and | |
3025 | represents the initial revision of a project. Each project must have | |
3026 | at least one root. A project can also have multiple roots, though | |
3027 | that isn't common (or necessarily a good idea). | |
3028 | - an author: The name of the person responsible for this change, together | |
3029 | with its date. | |
3030 | - a committer: The name of the person who actually created the commit, | |
3031 | with the date it was done. This may be different from the author, for | |
3032 | example, if the author was someone who wrote a patch and emailed it | |
3033 | to the person who used it to create the commit. | |
3034 | - a comment describing this commit. | |
3035 | ||
3036 | Note that a commit does not itself contain any information about what | |
3037 | actually changed; all changes are calculated by comparing the contents | |
3038 | of the tree referred to by this commit with the trees associated with | |
2de9b711 | 3039 | its parents. In particular, Git does not attempt to record file renames |
1bbf1c79 BF |
3040 | explicitly, though it can identify cases where the existence of the same |
3041 | file data at changing paths suggests a rename. (See, for example, the | |
1249d8ad | 3042 | `-M` option to linkgit:git-diff[1]). |
1bbf1c79 | 3043 | |
5162e697 | 3044 | A commit is usually created by linkgit:git-commit[1], which creates a |
1bbf1c79 BF |
3045 | commit whose parent is normally the current HEAD, and whose tree is |
3046 | taken from the content currently stored in the index. | |
b181d57f | 3047 | |
e34caace | 3048 | [[tree-object]] |
b181d57f | 3049 | Tree Object |
971aa71f | 3050 | ~~~~~~~~~~~ |
b181d57f | 3051 | |
5162e697 DM |
3052 | The ever-versatile linkgit:git-show[1] command can also be used to |
3053 | examine tree objects, but linkgit:git-ls-tree[1] will give you more | |
1bbf1c79 BF |
3054 | details: |
3055 | ||
3056 | ------------------------------------------------ | |
3057 | $ git ls-tree fb3a8bdd0ce | |
3058 | 100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore | |
3059 | 100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap | |
3060 | 100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING | |
3061 | 040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation | |
3062 | 100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN | |
3063 | 100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL | |
3064 | 100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile | |
3065 | 100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README | |
3066 | ... | |
3067 | ------------------------------------------------ | |
3068 | ||
3069 | As you can see, a tree object contains a list of entries, each with a | |
a6e5ef7d | 3070 | mode, object type, SHA-1 name, and name, sorted by name. It represents |
1bbf1c79 BF |
3071 | the contents of a single directory tree. |
3072 | ||
3073 | The object type may be a blob, representing the contents of a file, or | |
3074 | another tree, representing the contents of a subdirectory. Since trees | |
a6e5ef7d FC |
3075 | and blobs, like all other objects, are named by the SHA-1 hash of their |
3076 | contents, two trees have the same SHA-1 name if and only if their | |
1bbf1c79 | 3077 | contents (including, recursively, the contents of all subdirectories) |
2de9b711 | 3078 | are identical. This allows Git to quickly determine the differences |
1bbf1c79 BF |
3079 | between two related tree objects, since it can ignore any entries with |
3080 | identical object names. | |
3081 | ||
3082 | (Note: in the presence of submodules, trees may also have commits as | |
6dd14366 | 3083 | entries. See <<submodules>> for documentation.) |
1bbf1c79 | 3084 | |
2de9b711 | 3085 | Note that the files all have mode 644 or 755: Git actually only pays |
1bbf1c79 | 3086 | attention to the executable bit. |
b181d57f | 3087 | |
513d419c BF |
3088 | [[blob-object]] |
3089 | Blob Object | |
3090 | ~~~~~~~~~~~ | |
b181d57f | 3091 | |
5162e697 | 3092 | You can use linkgit:git-show[1] to examine the contents of a blob; take, |
1249d8ad | 3093 | for example, the blob in the entry for `COPYING` from the tree above: |
b181d57f | 3094 | |
1bbf1c79 BF |
3095 | ------------------------------------------------ |
3096 | $ git show 6ff87c4664 | |
3097 | ||
3098 | Note that the only valid version of the GPL as far as this project | |
3099 | is concerned is _this_ particular version of the license (ie v2, not | |
3100 | v2.2 or v3.x or whatever), unless explicitly otherwise stated. | |
3101 | ... | |
3102 | ------------------------------------------------ | |
b181d57f | 3103 | |
1bbf1c79 BF |
3104 | A "blob" object is nothing but a binary blob of data. It doesn't refer |
3105 | to anything else or have attributes of any kind. | |
3106 | ||
3107 | Since the blob is entirely defined by its data, if two files in a | |
3108 | directory tree (or in multiple different versions of the repository) | |
3109 | have the same contents, they will share the same blob object. The object | |
3110 | is totally independent of its location in the directory tree, and | |
3111 | renaming a file does not change the object that file is associated with. | |
3112 | ||
3113 | Note that any tree or blob object can be examined using | |
5162e697 | 3114 | linkgit:git-show[1] with the <revision>:<path> syntax. This can |
1bbf1c79 BF |
3115 | sometimes be useful for browsing the contents of a tree that is not |
3116 | currently checked out. | |
b181d57f | 3117 | |
e34caace | 3118 | [[trust]] |
b181d57f | 3119 | Trust |
971aa71f | 3120 | ~~~~~ |
b181d57f | 3121 | |
a6e5ef7d | 3122 | If you receive the SHA-1 name of a blob from one source, and its contents |
1bbf1c79 | 3123 | from another (possibly untrusted) source, you can still trust that those |
a6e5ef7d FC |
3124 | contents are correct as long as the SHA-1 name agrees. This is because |
3125 | the SHA-1 is designed so that it is infeasible to find different contents | |
1bbf1c79 | 3126 | that produce the same hash. |
b181d57f | 3127 | |
a6e5ef7d | 3128 | Similarly, you need only trust the SHA-1 name of a top-level tree object |
1bbf1c79 | 3129 | to trust the contents of the entire directory that it refers to, and if |
a6e5ef7d | 3130 | you receive the SHA-1 name of a commit from a trusted source, then you |
1bbf1c79 BF |
3131 | can easily verify the entire history of commits reachable through |
3132 | parents of that commit, and all of those contents of the trees referred | |
3133 | to by those commits. | |
b181d57f BF |
3134 | |
3135 | So to introduce some real trust in the system, the only thing you need | |
3136 | to do is to digitally sign just 'one' special note, which includes the | |
3137 | name of a top-level commit. Your digital signature shows others | |
3138 | that you trust that commit, and the immutability of the history of | |
3139 | commits tells others that they can trust the whole history. | |
3140 | ||
3141 | In other words, you can easily validate a whole archive by just | |
a6e5ef7d | 3142 | sending out a single email that tells the people the name (SHA-1 hash) |
b181d57f BF |
3143 | of the top commit, and digitally sign that email using something |
3144 | like GPG/PGP. | |
3145 | ||
2de9b711 | 3146 | To assist in this, Git also provides the tag object... |
b181d57f | 3147 | |
e34caace | 3148 | [[tag-object]] |
b181d57f | 3149 | Tag Object |
971aa71f | 3150 | ~~~~~~~~~~ |
b181d57f | 3151 | |
1bbf1c79 BF |
3152 | A tag object contains an object, object type, tag name, the name of the |
3153 | person ("tagger") who created the tag, and a message, which may contain | |
843c81dc | 3154 | a signature, as can be seen using linkgit:git-cat-file[1]: |
b181d57f | 3155 | |
1bbf1c79 BF |
3156 | ------------------------------------------------ |
3157 | $ git cat-file tag v1.5.0 | |
3158 | object 437b1b20df4b356c9342dac8d38849f24ef44f27 | |
3159 | type commit | |
3160 | tag v1.5.0 | |
3161 | tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000 | |
3162 | ||
3163 | GIT 1.5.0 | |
3164 | -----BEGIN PGP SIGNATURE----- | |
3165 | Version: GnuPG v1.4.6 (GNU/Linux) | |
3166 | ||
3167 | iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui | |
3168 | nLE/L9aUXdWeTFPron96DLA= | |
3169 | =2E+0 | |
3170 | -----END PGP SIGNATURE----- | |
3171 | ------------------------------------------------ | |
b181d57f | 3172 | |
5162e697 DM |
3173 | See the linkgit:git-tag[1] command to learn how to create and verify tag |
3174 | objects. (Note that linkgit:git-tag[1] can also be used to create | |
1bbf1c79 | 3175 | "lightweight tags", which are not tag objects at all, but just simple |
1249d8ad | 3176 | references whose names begin with `refs/tags/`). |
b181d57f | 3177 | |
09eff7b0 | 3178 | [[pack-files]] |
2de9b711 | 3179 | How Git stores objects efficiently: pack files |
09eff7b0 BF |
3180 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
3181 | ||
9644ffdd | 3182 | Newly created objects are initially created in a file named after the |
1249d8ad | 3183 | object's SHA-1 hash (stored in `.git/objects`). |
09eff7b0 BF |
3184 | |
3185 | Unfortunately this system becomes inefficient once a project has a | |
3186 | lot of objects. Try this on an old project: | |
3187 | ||
3188 | ------------------------------------------------ | |
3189 | $ git count-objects | |
3190 | 6930 objects, 47620 kilobytes | |
3191 | ------------------------------------------------ | |
3192 | ||
3193 | The first number is the number of objects which are kept in | |
3194 | individual files. The second is the amount of space taken up by | |
3195 | those "loose" objects. | |
3196 | ||
2de9b711 | 3197 | You can save space and make Git faster by moving these loose objects in |
09eff7b0 BF |
3198 | to a "pack file", which stores a group of objects in an efficient |
3199 | compressed format; the details of how pack files are formatted can be | |
3200 | found in link:technical/pack-format.txt[technical/pack-format.txt]. | |
3201 | ||
3202 | To put the loose objects into a pack, just run git repack: | |
3203 | ||
3204 | ------------------------------------------------ | |
3205 | $ git repack | |
3e65ac49 TA |
3206 | Counting objects: 6020, done. |
3207 | Delta compression using up to 4 threads. | |
3208 | Compressing objects: 100% (6020/6020), done. | |
3209 | Writing objects: 100% (6020/6020), done. | |
3210 | Total 6020 (delta 4070), reused 0 (delta 0) | |
09eff7b0 BF |
3211 | ------------------------------------------------ |
3212 | ||
3e65ac49 TA |
3213 | This creates a single "pack file" in .git/objects/pack/ |
3214 | containing all currently unpacked objects. You can then run | |
09eff7b0 BF |
3215 | |
3216 | ------------------------------------------------ | |
3217 | $ git prune | |
3218 | ------------------------------------------------ | |
3219 | ||
3220 | to remove any of the "loose" objects that are now contained in the | |
3221 | pack. This will also remove any unreferenced objects (which may be | |
1249d8ad | 3222 | created when, for example, you use `git reset` to remove a commit). |
09eff7b0 | 3223 | You can verify that the loose objects are gone by looking at the |
1249d8ad | 3224 | `.git/objects` directory or by running |
09eff7b0 BF |
3225 | |
3226 | ------------------------------------------------ | |
3227 | $ git count-objects | |
3228 | 0 objects, 0 kilobytes | |
3229 | ------------------------------------------------ | |
3230 | ||
3231 | Although the object files are gone, any commands that refer to those | |
3232 | objects will work exactly as they did before. | |
3233 | ||
5162e697 | 3234 | The linkgit:git-gc[1] command performs packing, pruning, and more for |
09eff7b0 BF |
3235 | you, so is normally the only high-level command you need. |
3236 | ||
3237 | [[dangling-objects]] | |
3238 | Dangling objects | |
3239 | ~~~~~~~~~~~~~~~~ | |
3240 | ||
5162e697 | 3241 | The linkgit:git-fsck[1] command will sometimes complain about dangling |
09eff7b0 BF |
3242 | objects. They are not a problem. |
3243 | ||
3244 | The most common cause of dangling objects is that you've rebased a | |
3245 | branch, or you have pulled from somebody else who rebased a branch--see | |
3246 | <<cleaning-up-history>>. In that case, the old head of the original | |
3247 | branch still exists, as does everything it pointed to. The branch | |
3248 | pointer itself just doesn't, since you replaced it with another one. | |
3249 | ||
3250 | There are also other situations that cause dangling objects. For | |
1249d8ad | 3251 | example, a "dangling blob" may arise because you did a `git add` of a |
09eff7b0 BF |
3252 | file, but then, before you actually committed it and made it part of the |
3253 | bigger picture, you changed something else in that file and committed | |
2ef8ac1b | 3254 | that *updated* thing--the old state that you added originally ends up |
09eff7b0 BF |
3255 | not being pointed to by any commit or tree, so it's now a dangling blob |
3256 | object. | |
3257 | ||
3258 | Similarly, when the "recursive" merge strategy runs, and finds that | |
3259 | there are criss-cross merges and thus more than one merge base (which is | |
3260 | fairly unusual, but it does happen), it will generate one temporary | |
3261 | midway tree (or possibly even more, if you had lots of criss-crossing | |
3262 | merges and more than two merge bases) as a temporary internal merge | |
3263 | base, and again, those are real objects, but the end result will not end | |
3264 | up pointing to them, so they end up "dangling" in your repository. | |
3265 | ||
3266 | Generally, dangling objects aren't anything to worry about. They can | |
3267 | even be very useful: if you screw something up, the dangling objects can | |
3268 | be how you recover your old tree (say, you did a rebase, and realized | |
2ef8ac1b | 3269 | that you really didn't want to--you can look at what dangling objects |
09eff7b0 BF |
3270 | you have, and decide to reset your head to some old dangling state). |
3271 | ||
3272 | For commits, you can just use: | |
3273 | ||
3274 | ------------------------------------------------ | |
3275 | $ gitk <dangling-commit-sha-goes-here> --not --all | |
3276 | ------------------------------------------------ | |
3277 | ||
3278 | This asks for all the history reachable from the given commit but not | |
3279 | from any branch, tag, or other reference. If you decide it's something | |
3280 | you want, you can always create a new reference to it, e.g., | |
3281 | ||
3282 | ------------------------------------------------ | |
3283 | $ git branch recovered-branch <dangling-commit-sha-goes-here> | |
3284 | ------------------------------------------------ | |
3285 | ||
3286 | For blobs and trees, you can't do the same, but you can still examine | |
3287 | them. You can just do | |
3288 | ||
3289 | ------------------------------------------------ | |
3290 | $ git show <dangling-blob/tree-sha-goes-here> | |
3291 | ------------------------------------------------ | |
3292 | ||
3293 | to show what the contents of the blob were (or, for a tree, basically | |
1249d8ad | 3294 | what the `ls` for that directory was), and that may give you some idea |
09eff7b0 BF |
3295 | of what the operation was that left that dangling object. |
3296 | ||
3297 | Usually, dangling blobs and trees aren't very interesting. They're | |
3298 | almost always the result of either being a half-way mergebase (the blob | |
3299 | will often even have the conflict markers from a merge in it, if you | |
3300 | have had conflicting merges that you fixed up by hand), or simply | |
1249d8ad | 3301 | because you interrupted a `git fetch` with ^C or something like that, |
09eff7b0 BF |
3302 | leaving _some_ of the new objects in the object database, but just |
3303 | dangling and useless. | |
3304 | ||
3305 | Anyway, once you are sure that you're not interested in any dangling | |
3306 | state, you can just prune all unreachable objects: | |
3307 | ||
3308 | ------------------------------------------------ | |
3309 | $ git prune | |
3310 | ------------------------------------------------ | |
3311 | ||
1249d8ad | 3312 | and they'll be gone. But you should only run `git prune` on a quiescent |
2ef8ac1b | 3313 | repository--it's kind of like doing a filesystem fsck recovery: you |
09eff7b0 BF |
3314 | don't want to do that while the filesystem is mounted. |
3315 | ||
1249d8ad | 3316 | (The same is true of `git fsck` itself, btw, but since |
6127c086 FC |
3317 | `git fsck` never actually *changes* the repository, it just reports |
3318 | on what it found, `git fsck` itself is never 'dangerous' to run. | |
09eff7b0 BF |
3319 | Running it while somebody is actually changing the repository can cause |
3320 | confusing and scary messages, but it won't actually do anything bad. In | |
1249d8ad | 3321 | contrast, running `git prune` while somebody is actively changing the |
09eff7b0 | 3322 | repository is a *BAD* idea). |
b181d57f | 3323 | |
1cdade2c BF |
3324 | [[recovering-from-repository-corruption]] |
3325 | Recovering from repository corruption | |
3326 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3327 | ||
2de9b711 TA |
3328 | By design, Git treats data trusted to it with caution. However, even in |
3329 | the absence of bugs in Git itself, it is still possible that hardware or | |
1cdade2c BF |
3330 | operating system errors could corrupt data. |
3331 | ||
3332 | The first defense against such problems is backups. You can back up a | |
2de9b711 | 3333 | Git directory using clone, or just using cp, tar, or any other backup |
1cdade2c BF |
3334 | mechanism. |
3335 | ||
3336 | As a last resort, you can search for the corrupted objects and attempt | |
3337 | to replace them by hand. Back up your repository before attempting this | |
3338 | in case you corrupt things even more in the process. | |
3339 | ||
3340 | We'll assume that the problem is a single missing or corrupted blob, | |
9e5d87d4 | 3341 | which is sometimes a solvable problem. (Recovering missing trees and |
1cdade2c BF |
3342 | especially commits is *much* harder). |
3343 | ||
3344 | Before starting, verify that there is corruption, and figure out where | |
5162e697 | 3345 | it is with linkgit:git-fsck[1]; this may be time-consuming. |
1cdade2c BF |
3346 | |
3347 | Assume the output looks like this: | |
3348 | ||
3349 | ------------------------------------------------ | |
c6a13b2c | 3350 | $ git fsck --full --no-dangling |
1cdade2c BF |
3351 | broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 |
3352 | to blob 4b9458b3786228369c63936db65827de3cc06200 | |
3353 | missing blob 4b9458b3786228369c63936db65827de3cc06200 | |
3354 | ------------------------------------------------ | |
3355 | ||
1cdade2c BF |
3356 | Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6 |
3357 | points to it. If you could find just one copy of that missing blob | |
3358 | object, possibly in some other repository, you could move it into | |
1249d8ad | 3359 | `.git/objects/4b/9458b3...` and be done. Suppose you can't. You can |
5162e697 | 3360 | still examine the tree that pointed to it with linkgit:git-ls-tree[1], |
1cdade2c BF |
3361 | which might output something like: |
3362 | ||
3363 | ------------------------------------------------ | |
3364 | $ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 | |
3365 | 100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore | |
3366 | 100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap | |
3367 | 100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING | |
3368 | ... | |
3369 | 100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile | |
3370 | ... | |
3371 | ------------------------------------------------ | |
3372 | ||
3373 | So now you know that the missing blob was the data for a file named | |
1249d8ad TK |
3374 | `myfile`. And chances are you can also identify the directory--let's |
3375 | say it's in `somedirectory`. If you're lucky the missing copy might be | |
1cdade2c | 3376 | the same as the copy you have checked out in your working tree at |
1249d8ad | 3377 | `somedirectory/myfile`; you can test whether that's right with |
5162e697 | 3378 | linkgit:git-hash-object[1]: |
1cdade2c BF |
3379 | |
3380 | ------------------------------------------------ | |
3381 | $ git hash-object -w somedirectory/myfile | |
3382 | ------------------------------------------------ | |
3383 | ||
3384 | which will create and store a blob object with the contents of | |
a6e5ef7d | 3385 | somedirectory/myfile, and output the SHA-1 of that object. if you're |
1cdade2c BF |
3386 | extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in |
3387 | which case you've guessed right, and the corruption is fixed! | |
3388 | ||
3389 | Otherwise, you need more information. How do you tell which version of | |
3390 | the file has been lost? | |
3391 | ||
3392 | The easiest way to do this is with: | |
3393 | ||
3394 | ------------------------------------------------ | |
3395 | $ git log --raw --all --full-history -- somedirectory/myfile | |
3396 | ------------------------------------------------ | |
3397 | ||
3398 | Because you're asking for raw output, you'll now get something like | |
3399 | ||
3400 | ------------------------------------------------ | |
3401 | commit abc | |
3402 | Author: | |
3403 | Date: | |
3404 | ... | |
3405 | :100644 100644 4b9458b... newsha... M somedirectory/myfile | |
3406 | ||
3407 | ||
3408 | commit xyz | |
3409 | Author: | |
3410 | Date: | |
3411 | ||
3412 | ... | |
3413 | :100644 100644 oldsha... 4b9458b... M somedirectory/myfile | |
3414 | ------------------------------------------------ | |
3415 | ||
edfbbf7e ŠN |
3416 | This tells you that the immediately following version of the file was |
3417 | "newsha", and that the immediately preceding version was "oldsha". | |
1cdade2c BF |
3418 | You also know the commit messages that went with the change from oldsha |
3419 | to 4b9458b and with the change from 4b9458b to newsha. | |
3420 | ||
3421 | If you've been committing small enough changes, you may now have a good | |
3422 | shot at reconstructing the contents of the in-between state 4b9458b. | |
3423 | ||
3424 | If you can do that, you can now recreate the missing object with | |
3425 | ||
3426 | ------------------------------------------------ | |
3427 | $ git hash-object -w <recreated-file> | |
3428 | ------------------------------------------------ | |
3429 | ||
3430 | and your repository is good again! | |
3431 | ||
1249d8ad | 3432 | (Btw, you could have ignored the `fsck`, and started with doing a |
1cdade2c BF |
3433 | |
3434 | ------------------------------------------------ | |
3435 | $ git log --raw --all | |
3436 | ------------------------------------------------ | |
3437 | ||
1ab58e8d | 3438 | and just looked for the sha of the missing object (4b9458b..) in that |
da2c7b3d | 3439 | whole thing. It's up to you--Git does *have* a lot of information, it is |
1cdade2c BF |
3440 | just missing one particular blob version. |
3441 | ||
e34caace | 3442 | [[the-index]] |
1c097891 BF |
3443 | The index |
3444 | ----------- | |
3445 | ||
1249d8ad | 3446 | The index is a binary file (generally kept in `.git/index`) containing a |
a6e5ef7d | 3447 | sorted list of path names, each with permissions and the SHA-1 of a blob |
5162e697 | 3448 | object; linkgit:git-ls-files[1] can show you the contents of the index: |
b181d57f | 3449 | |
1c097891 BF |
3450 | ------------------------------------------------- |
3451 | $ git ls-files --stage | |
3452 | 100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore | |
3453 | 100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap | |
3454 | 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING | |
3455 | 100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore | |
3456 | 100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile | |
3457 | ... | |
3458 | 100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h | |
3459 | 100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c | |
3460 | 100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h | |
3461 | ------------------------------------------------- | |
3462 | ||
3463 | Note that in older documentation you may see the index called the | |
3464 | "current directory cache" or just the "cache". It has three important | |
3465 | properties: | |
3466 | ||
3467 | 1. The index contains all the information necessary to generate a single | |
3468 | (uniquely determined) tree object. | |
3469 | + | |
5162e697 | 3470 | For example, running linkgit:git-commit[1] generates this tree object |
1c097891 BF |
3471 | from the index, stores it in the object database, and uses it as the |
3472 | tree object associated with the new commit. | |
3473 | ||
3474 | 2. The index enables fast comparisons between the tree object it defines | |
3475 | and the working tree. | |
3476 | + | |
3477 | It does this by storing some additional data for each entry (such as | |
3478 | the last modified time). This data is not displayed above, and is not | |
3479 | stored in the created tree object, but it can be used to determine | |
3480 | quickly which files in the working directory differ from what was | |
2de9b711 | 3481 | stored in the index, and thus save Git from having to read all of the |
1c097891 BF |
3482 | data from such files to look for changes. |
3483 | ||
3484 | 3. It can efficiently represent information about merge conflicts | |
3485 | between different tree objects, allowing each pathname to be | |
b181d57f | 3486 | associated with sufficient information about the trees involved that |
1c097891 BF |
3487 | you can create a three-way merge between them. |
3488 | + | |
3489 | We saw in <<conflict-resolution>> that during a merge the index can | |
3490 | store multiple versions of a single file (called "stages"). The third | |
5162e697 | 3491 | column in the linkgit:git-ls-files[1] output above is the stage |
1c097891 BF |
3492 | number, and will take on values other than 0 for files with merge |
3493 | conflicts. | |
3494 | ||
3495 | The index is thus a sort of temporary staging area, which is filled with | |
3496 | a tree which you are in the process of working on. | |
3497 | ||
3498 | If you blow the index away entirely, you generally haven't lost any | |
3499 | information as long as you have the name of the tree that it described. | |
b181d57f | 3500 | |
38a457ba MV |
3501 | [[submodules]] |
3502 | Submodules | |
3503 | ========== | |
3504 | ||
6dd14366 MS |
3505 | Large projects are often composed of smaller, self-contained modules. For |
3506 | example, an embedded Linux distribution's source tree would include every | |
3507 | piece of software in the distribution with some local modifications; a movie | |
3508 | player might need to build against a specific, known-working version of a | |
3509 | decompression library; several independent programs might all share the same | |
3510 | build scripts. | |
3511 | ||
3512 | With centralized revision control systems this is often accomplished by | |
3513 | including every module in one single repository. Developers can check out | |
3514 | all modules or only the modules they need to work with. They can even modify | |
3515 | files across several modules in a single commit while moving things around | |
3516 | or updating APIs and translations. | |
3517 | ||
3518 | Git does not allow partial checkouts, so duplicating this approach in Git | |
3519 | would force developers to keep a local copy of modules they are not | |
3520 | interested in touching. Commits in an enormous checkout would be slower | |
3521 | than you'd expect as Git would have to scan every directory for changes. | |
3522 | If modules have a lot of local history, clones would take forever. | |
3523 | ||
3524 | On the plus side, distributed revision control systems can much better | |
3525 | integrate with external sources. In a centralized model, a single arbitrary | |
3526 | snapshot of the external project is exported from its own revision control | |
3527 | and then imported into the local revision control on a vendor branch. All | |
3528 | the history is hidden. With distributed revision control you can clone the | |
3529 | entire external history and much more easily follow development and re-merge | |
3530 | local changes. | |
3531 | ||
3532 | Git's submodule support allows a repository to contain, as a subdirectory, a | |
3533 | checkout of an external project. Submodules maintain their own identity; | |
3534 | the submodule support just stores the submodule repository location and | |
3535 | commit ID, so other developers who clone the containing project | |
3536 | ("superproject") can easily clone all the submodules at the same revision. | |
3537 | Partial checkouts of the superproject are possible: you can tell Git to | |
3538 | clone none, some or all of the submodules. | |
3539 | ||
5162e697 | 3540 | The linkgit:git-submodule[1] command is available since Git 1.5.3. Users |
6dd14366 MS |
3541 | with Git 1.5.2 can look up the submodule commits in the repository and |
3542 | manually check them out; earlier versions won't recognize the submodules at | |
3543 | all. | |
38a457ba MV |
3544 | |
3545 | To see how submodule support works, create (for example) four example | |
3546 | repositories that can be used later as a submodule: | |
3547 | ||
3548 | ------------------------------------------------- | |
3549 | $ mkdir ~/git | |
3550 | $ cd ~/git | |
3551 | $ for i in a b c d | |
3552 | do | |
3553 | mkdir $i | |
3554 | cd $i | |
3555 | git init | |
3556 | echo "module $i" > $i.txt | |
3557 | git add $i.txt | |
3558 | git commit -m "Initial commit, submodule $i" | |
3559 | cd .. | |
3560 | done | |
3561 | ------------------------------------------------- | |
3562 | ||
3563 | Now create the superproject and add all the submodules: | |
3564 | ||
3565 | ------------------------------------------------- | |
3566 | $ mkdir super | |
3567 | $ cd super | |
3568 | $ git init | |
3569 | $ for i in a b c d | |
3570 | do | |
a56bf585 | 3571 | git submodule add ~/git/$i $i |
38a457ba MV |
3572 | done |
3573 | ------------------------------------------------- | |
3574 | ||
3575 | NOTE: Do not use local URLs here if you plan to publish your superproject! | |
3576 | ||
6127c086 | 3577 | See what files `git submodule` created: |
38a457ba MV |
3578 | |
3579 | ------------------------------------------------- | |
3580 | $ ls -a | |
3581 | . .. .git .gitmodules a b c d | |
3582 | ------------------------------------------------- | |
3583 | ||
6127c086 | 3584 | The `git submodule add <repo> <path>` command does a couple of things: |
38a457ba | 3585 | |
1249d8ad | 3586 | - It clones the submodule from `<repo>` to the given `<path>` under the |
a56bf585 | 3587 | current directory and by default checks out the master branch. |
5162e697 | 3588 | - It adds the submodule's clone path to the linkgit:gitmodules[5] file and |
6dd14366 | 3589 | adds this file to the index, ready to be committed. |
38a457ba MV |
3590 | - It adds the submodule's current commit ID to the index, ready to be |
3591 | committed. | |
3592 | ||
3593 | Commit the superproject: | |
3594 | ||
3595 | ------------------------------------------------- | |
3596 | $ git commit -m "Add submodules a, b, c and d." | |
3597 | ------------------------------------------------- | |
3598 | ||
3599 | Now clone the superproject: | |
3600 | ||
3601 | ------------------------------------------------- | |
3602 | $ cd .. | |
3603 | $ git clone super cloned | |
3604 | $ cd cloned | |
3605 | ------------------------------------------------- | |
3606 | ||
3607 | The submodule directories are there, but they're empty: | |
3608 | ||
3609 | ------------------------------------------------- | |
3610 | $ ls -a a | |
3611 | . .. | |
3612 | $ git submodule status | |
3613 | -d266b9873ad50488163457f025db7cdd9683d88b a | |
3614 | -e81d457da15309b4fef4249aba9b50187999670d b | |
3615 | -c1536a972b9affea0f16e0680ba87332dc059146 c | |
3616 | -d96249ff5d57de5de093e6baff9e0aafa5276a74 d | |
3617 | ------------------------------------------------- | |
3618 | ||
3619 | NOTE: The commit object names shown above would be different for you, but they | |
3620 | should match the HEAD commit object names of your repositories. You can check | |
3621 | it by running `git ls-remote ../a`. | |
3622 | ||
3623 | Pulling down the submodules is a two-step process. First run `git submodule | |
3624 | init` to add the submodule repository URLs to `.git/config`: | |
3625 | ||
3626 | ------------------------------------------------- | |
3627 | $ git submodule init | |
3628 | ------------------------------------------------- | |
3629 | ||
6127c086 | 3630 | Now use `git submodule update` to clone the repositories and check out the |
38a457ba MV |
3631 | commits specified in the superproject: |
3632 | ||
3633 | ------------------------------------------------- | |
3634 | $ git submodule update | |
3635 | $ cd a | |
3636 | $ ls -a | |
3637 | . .. .git a.txt | |
3638 | ------------------------------------------------- | |
3639 | ||
6127c086 FC |
3640 | One major difference between `git submodule update` and `git submodule add` is |
3641 | that `git submodule update` checks out a specific commit, rather than the tip | |
38a457ba MV |
3642 | of a branch. It's like checking out a tag: the head is detached, so you're not |
3643 | working on a branch. | |
3644 | ||
3645 | ------------------------------------------------- | |
3646 | $ git branch | |
95f9be55 | 3647 | * (detached from d266b98) |
38a457ba MV |
3648 | master |
3649 | ------------------------------------------------- | |
3650 | ||
3651 | If you want to make a change within a submodule and you have a detached head, | |
3652 | then you should create or checkout a branch, make your changes, publish the | |
3653 | change within the submodule, and then update the superproject to reference the | |
3654 | new commit: | |
3655 | ||
3656 | ------------------------------------------------- | |
3657 | $ git checkout master | |
3658 | ------------------------------------------------- | |
3659 | ||
3660 | or | |
3661 | ||
3662 | ------------------------------------------------- | |
3663 | $ git checkout -b fix-up | |
3664 | ------------------------------------------------- | |
3665 | ||
3666 | then | |
3667 | ||
3668 | ------------------------------------------------- | |
3669 | $ echo "adding a line again" >> a.txt | |
3670 | $ git commit -a -m "Updated the submodule from within the superproject." | |
3671 | $ git push | |
3672 | $ cd .. | |
3673 | $ git diff | |
3674 | diff --git a/a b/a | |
3675 | index d266b98..261dfac 160000 | |
3676 | --- a/a | |
3677 | +++ b/a | |
3678 | @@ -1 +1 @@ | |
3679 | -Subproject commit d266b9873ad50488163457f025db7cdd9683d88b | |
3680 | +Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24 | |
3681 | $ git add a | |
3682 | $ git commit -m "Updated submodule a." | |
3683 | $ git push | |
3684 | ------------------------------------------------- | |
3685 | ||
3686 | You have to run `git submodule update` after `git pull` if you want to update | |
3687 | submodules, too. | |
3688 | ||
3689 | Pitfalls with submodules | |
3690 | ------------------------ | |
3691 | ||
3692 | Always publish the submodule change before publishing the change to the | |
3693 | superproject that references it. If you forget to publish the submodule change, | |
3694 | others won't be able to clone the repository: | |
3695 | ||
3696 | ------------------------------------------------- | |
3697 | $ cd ~/git/super/a | |
3698 | $ echo i added another line to this file >> a.txt | |
3699 | $ git commit -a -m "doing it wrong this time" | |
3700 | $ cd .. | |
3701 | $ git add a | |
3702 | $ git commit -m "Updated submodule a again." | |
3703 | $ git push | |
3704 | $ cd ~/git/cloned | |
3705 | $ git pull | |
3706 | $ git submodule update | |
3707 | error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git. | |
3708 | Did you forget to 'git add'? | |
3709 | Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a' | |
3710 | ------------------------------------------------- | |
3711 | ||
2de9b711 | 3712 | In older Git versions it could be easily forgotten to commit new or modified |
8d9e7d52 | 3713 | files in a submodule, which silently leads to similar problems as not pushing |
1249d8ad | 3714 | the submodule changes. Starting with Git 1.7.0 both `git status` and `git diff` |
8d9e7d52 | 3715 | in the superproject show submodules as modified when they contain new or |
1249d8ad TK |
3716 | modified files to protect against accidentally committing such a state. `git |
3717 | diff` will also add a `-dirty` to the work tree side when generating patch | |
3718 | output or used with the `--submodule` option: | |
8d9e7d52 JL |
3719 | |
3720 | ------------------------------------------------- | |
3721 | $ git diff | |
3722 | diff --git a/sub b/sub | |
3723 | --- a/sub | |
3724 | +++ b/sub | |
3725 | @@ -1 +1 @@ | |
3726 | -Subproject commit 3f356705649b5d566d97ff843cf193359229a453 | |
3727 | +Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty | |
3728 | $ git diff --submodule | |
3729 | Submodule sub 3f35670..3f35670-dirty: | |
3730 | ------------------------------------------------- | |
3731 | ||
38a457ba MV |
3732 | You also should not rewind branches in a submodule beyond commits that were |
3733 | ever recorded in any superproject. | |
3734 | ||
3735 | It's not safe to run `git submodule update` if you've made and committed | |
3736 | changes within a submodule without checking out a branch first. They will be | |
3737 | silently overwritten: | |
3738 | ||
3739 | ------------------------------------------------- | |
3740 | $ cat a.txt | |
3741 | module a | |
3742 | $ echo line added from private2 >> a.txt | |
3743 | $ git commit -a -m "line added inside private2" | |
3744 | $ cd .. | |
3745 | $ git submodule update | |
3746 | Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b' | |
3747 | $ cd a | |
3748 | $ cat a.txt | |
3749 | module a | |
3750 | ------------------------------------------------- | |
3751 | ||
3752 | NOTE: The changes are still visible in the submodule's reflog. | |
3753 | ||
91486733 TK |
3754 | If you have uncommitted changes in your submodule working tree, `git |
3755 | submodule update` will not overwrite them. Instead, you get the usual | |
3756 | warning about not being able switch from a dirty branch. | |
38a457ba | 3757 | |
1c6045ff | 3758 | [[low-level-operations]] |
2de9b711 | 3759 | Low-level Git operations |
1c6045ff | 3760 | ======================== |
b181d57f | 3761 | |
1c6045ff | 3762 | Many of the higher-level commands were originally implemented as shell |
2de9b711 TA |
3763 | scripts using a smaller core of low-level Git commands. These can still |
3764 | be useful when doing unusual things with Git, or just as a way to | |
1c6045ff | 3765 | understand its inner workings. |
b181d57f | 3766 | |
1bbf1c79 BF |
3767 | [[object-manipulation]] |
3768 | Object access and manipulation | |
3769 | ------------------------------ | |
3770 | ||
5162e697 DM |
3771 | The linkgit:git-cat-file[1] command can show the contents of any object, |
3772 | though the higher-level linkgit:git-show[1] is usually more useful. | |
1bbf1c79 | 3773 | |
5162e697 | 3774 | The linkgit:git-commit-tree[1] command allows constructing commits with |
1bbf1c79 BF |
3775 | arbitrary parents and trees. |
3776 | ||
5162e697 DM |
3777 | A tree can be created with linkgit:git-write-tree[1] and its data can be |
3778 | accessed by linkgit:git-ls-tree[1]. Two trees can be compared with | |
3779 | linkgit:git-diff-tree[1]. | |
1bbf1c79 | 3780 | |
5162e697 DM |
3781 | A tag is created with linkgit:git-mktag[1], and the signature can be |
3782 | verified by linkgit:git-verify-tag[1], though it is normally simpler to | |
3783 | use linkgit:git-tag[1] for both. | |
1bbf1c79 | 3784 | |
e34caace | 3785 | [[the-workflow]] |
b181d57f BF |
3786 | The Workflow |
3787 | ------------ | |
3788 | ||
5162e697 DM |
3789 | High-level operations such as linkgit:git-commit[1], |
3790 | linkgit:git-checkout[1] and linkgit:git-reset[1] work by moving data | |
06ada152 RW |
3791 | between the working tree, the index, and the object database. Git |
3792 | provides low-level operations which perform each of these steps | |
3793 | individually. | |
1c6045ff | 3794 | |
2de9b711 | 3795 | Generally, all Git operations work on the index file. Some operations |
b181d57f | 3796 | work *purely* on the index file (showing the current state of the |
1c6045ff BF |
3797 | index), but most operations move data between the index file and either |
3798 | the database or the working directory. Thus there are four main | |
3799 | combinations: | |
b181d57f | 3800 | |
e34caace | 3801 | [[working-directory-to-index]] |
b181d57f BF |
3802 | working directory -> index |
3803 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3804 | ||
5162e697 | 3805 | The linkgit:git-update-index[1] command updates the index with |
1c6045ff BF |
3806 | information from the working directory. You generally update the |
3807 | index information by just specifying the filename you want to update, | |
3808 | like so: | |
b181d57f BF |
3809 | |
3810 | ------------------------------------------------- | |
1c6045ff | 3811 | $ git update-index filename |
b181d57f BF |
3812 | ------------------------------------------------- |
3813 | ||
3814 | but to avoid common mistakes with filename globbing etc, the command | |
3815 | will not normally add totally new entries or remove old entries, | |
3816 | i.e. it will normally just update existing cache entries. | |
3817 | ||
2de9b711 | 3818 | To tell Git that yes, you really do realize that certain files no |
b181d57f BF |
3819 | longer exist, or that new files should be added, you |
3820 | should use the `--remove` and `--add` flags respectively. | |
3821 | ||
3822 | NOTE! A `--remove` flag does 'not' mean that subsequent filenames will | |
3823 | necessarily be removed: if the files still exist in your directory | |
3824 | structure, the index will be updated with their new status, not | |
10455d2a | 3825 | removed. The only thing `--remove` means is that update-index will be |
b181d57f BF |
3826 | considering a removed file to be a valid thing, and if the file really |
3827 | does not exist any more, it will update the index accordingly. | |
3828 | ||
467c0197 | 3829 | As a special case, you can also do `git update-index --refresh`, which |
b181d57f BF |
3830 | will refresh the "stat" information of each index to match the current |
3831 | stat information. It will 'not' update the object status itself, and | |
3832 | it will only update the fields that are used to quickly test whether | |
3833 | an object still matches its old backing store object. | |
3834 | ||
5162e697 DM |
3835 | The previously introduced linkgit:git-add[1] is just a wrapper for |
3836 | linkgit:git-update-index[1]. | |
1c6045ff | 3837 | |
e34caace | 3838 | [[index-to-object-database]] |
b181d57f BF |
3839 | index -> object database |
3840 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
3841 | ||
3842 | You write your current index file to a "tree" object with the program | |
3843 | ||
3844 | ------------------------------------------------- | |
1c6045ff | 3845 | $ git write-tree |
b181d57f BF |
3846 | ------------------------------------------------- |
3847 | ||
2ef8ac1b | 3848 | that doesn't come with any options--it will just write out the |
b181d57f BF |
3849 | current index into the set of tree objects that describe that state, |
3850 | and it will return the name of the resulting top-level tree. You can | |
3851 | use that tree to re-generate the index at any time by going in the | |
3852 | other direction: | |
3853 | ||
e34caace | 3854 | [[object-database-to-index]] |
b181d57f BF |
3855 | object database -> index |
3856 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
3857 | ||
3858 | You read a "tree" file from the object database, and use that to | |
2ef8ac1b | 3859 | populate (and overwrite--don't do this if your index contains any |
b181d57f BF |
3860 | unsaved state that you might want to restore later!) your current |
3861 | index. Normal operation is just | |
3862 | ||
3863 | ------------------------------------------------- | |
a6e5ef7d | 3864 | $ git read-tree <SHA-1 of tree> |
b181d57f BF |
3865 | ------------------------------------------------- |
3866 | ||
3867 | and your index file will now be equivalent to the tree that you saved | |
3868 | earlier. However, that is only your 'index' file: your working | |
3869 | directory contents have not been modified. | |
3870 | ||
e34caace | 3871 | [[index-to-working-directory]] |
b181d57f BF |
3872 | index -> working directory |
3873 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3874 | ||
3875 | You update your working directory from the index by "checking out" | |
3876 | files. This is not a very common operation, since normally you'd just | |
3877 | keep your files updated, and rather than write to your working | |
3878 | directory, you'd tell the index files about the changes in your | |
6127c086 | 3879 | working directory (i.e. `git update-index`). |
b181d57f BF |
3880 | |
3881 | However, if you decide to jump to a new version, or check out somebody | |
3882 | else's version, or just restore a previous tree, you'd populate your | |
3883 | index file with read-tree, and then you need to check out the result | |
3884 | with | |
3885 | ||
3886 | ------------------------------------------------- | |
b1889c36 | 3887 | $ git checkout-index filename |
b181d57f BF |
3888 | ------------------------------------------------- |
3889 | ||
3890 | or, if you want to check out all of the index, use `-a`. | |
3891 | ||
6127c086 | 3892 | NOTE! `git checkout-index` normally refuses to overwrite old files, so |
b181d57f | 3893 | if you have an old version of the tree already checked out, you will |
1249d8ad | 3894 | need to use the `-f` flag ('before' the `-a` flag or the filename) to |
b181d57f BF |
3895 | 'force' the checkout. |
3896 | ||
3897 | ||
3898 | Finally, there are a few odds and ends which are not purely moving | |
3899 | from one representation to the other: | |
3900 | ||
e34caace | 3901 | [[tying-it-all-together]] |
b181d57f BF |
3902 | Tying it all together |
3903 | ~~~~~~~~~~~~~~~~~~~~~ | |
3904 | ||
1249d8ad | 3905 | To commit a tree you have instantiated with `git write-tree`, you'd |
b181d57f | 3906 | create a "commit" object that refers to that tree and the history |
2ef8ac1b | 3907 | behind it--most notably the "parent" commits that preceded it in |
b181d57f BF |
3908 | history. |
3909 | ||
3910 | Normally a "commit" has one parent: the previous state of the tree | |
3911 | before a certain change was made. However, sometimes it can have two | |
3912 | or more parent commits, in which case we call it a "merge", due to the | |
3913 | fact that such a commit brings together ("merges") two or more | |
3914 | previous states represented by other commits. | |
3915 | ||
3916 | In other words, while a "tree" represents a particular directory state | |
3917 | of a working directory, a "commit" represents that state in "time", | |
3918 | and explains how we got there. | |
3919 | ||
3920 | You create a commit object by giving it the tree that describes the | |
3921 | state at the time of the commit, and a list of parents: | |
3922 | ||
3923 | ------------------------------------------------- | |
0adda936 | 3924 | $ git commit-tree <tree> -p <parent> [(-p <parent2>)...] |
b181d57f BF |
3925 | ------------------------------------------------- |
3926 | ||
3927 | and then giving the reason for the commit on stdin (either through | |
3928 | redirection from a pipe or file, or by just typing it at the tty). | |
3929 | ||
6127c086 | 3930 | `git commit-tree` will return the name of the object that represents |
b181d57f | 3931 | that commit, and you should save it away for later use. Normally, |
2de9b711 | 3932 | you'd commit a new `HEAD` state, and while Git doesn't care where you |
b181d57f BF |
3933 | save the note about that state, in practice we tend to just write the |
3934 | result to the file pointed at by `.git/HEAD`, so that we can always see | |
3935 | what the last committed state was. | |
3936 | ||
3937 | Here is an ASCII art by Jon Loeliger that illustrates how | |
3938 | various pieces fit together. | |
3939 | ||
3940 | ------------ | |
3941 | ||
3942 | commit-tree | |
3943 | commit obj | |
3944 | +----+ | |
3945 | | | | |
3946 | | | | |
3947 | V V | |
3948 | +-----------+ | |
3949 | | Object DB | | |
3950 | | Backing | | |
3951 | | Store | | |
3952 | +-----------+ | |
3953 | ^ | |
3954 | write-tree | | | |
3955 | tree obj | | | |
3956 | | | read-tree | |
3957 | | | tree obj | |
3958 | V | |
3959 | +-----------+ | |
3960 | | Index | | |
3961 | | "cache" | | |
3962 | +-----------+ | |
3963 | update-index ^ | |
3964 | blob obj | | | |
3965 | | | | |
3966 | checkout-index -u | | checkout-index | |
3967 | stat | | blob obj | |
3968 | V | |
3969 | +-----------+ | |
3970 | | Working | | |
3971 | | Directory | | |
3972 | +-----------+ | |
3973 | ||
3974 | ------------ | |
3975 | ||
3976 | ||
e34caace | 3977 | [[examining-the-data]] |
b181d57f BF |
3978 | Examining the data |
3979 | ------------------ | |
3980 | ||
3981 | You can examine the data represented in the object database and the | |
3982 | index with various helper tools. For every object, you can use | |
5162e697 | 3983 | linkgit:git-cat-file[1] to examine details about the |
b181d57f BF |
3984 | object: |
3985 | ||
3986 | ------------------------------------------------- | |
b1889c36 | 3987 | $ git cat-file -t <objectname> |
b181d57f BF |
3988 | ------------------------------------------------- |
3989 | ||
3990 | shows the type of the object, and once you have the type (which is | |
3991 | usually implicit in where you find the object), you can use | |
3992 | ||
3993 | ------------------------------------------------- | |
b1889c36 | 3994 | $ git cat-file blob|tree|commit|tag <objectname> |
b181d57f BF |
3995 | ------------------------------------------------- |
3996 | ||
3997 | to show its contents. NOTE! Trees have binary content, and as a result | |
3998 | there is a special helper for showing that content, called | |
6127c086 | 3999 | `git ls-tree`, which turns the binary content into a more easily |
b181d57f BF |
4000 | readable form. |
4001 | ||
4002 | It's especially instructive to look at "commit" objects, since those | |
4003 | tend to be small and fairly self-explanatory. In particular, if you | |
4004 | follow the convention of having the top commit name in `.git/HEAD`, | |
4005 | you can do | |
4006 | ||
4007 | ------------------------------------------------- | |
b1889c36 | 4008 | $ git cat-file commit HEAD |
b181d57f BF |
4009 | ------------------------------------------------- |
4010 | ||
4011 | to see what the top commit was. | |
4012 | ||
e34caace | 4013 | [[merging-multiple-trees]] |
b181d57f | 4014 | Merging multiple trees |
d19fbc3c BF |
4015 | ---------------------- |
4016 | ||
b181d57f BF |
4017 | Git helps you do a three-way merge, which you can expand to n-way by |
4018 | repeating the merge procedure arbitrary times until you finally | |
4019 | "commit" the state. The normal situation is that you'd only do one | |
4020 | three-way merge (two parents), and commit it, but if you like to, you | |
4021 | can do multiple parents in one go. | |
4022 | ||
4023 | To do a three-way merge, you need the two sets of "commit" objects | |
4024 | that you want to merge, use those to find the closest common parent (a | |
4025 | third "commit" object), and then use those commit objects to find the | |
4026 | state of the directory ("tree" object) at these points. | |
4027 | ||
4028 | To get the "base" for the merge, you first look up the common parent | |
4029 | of two commits with | |
4030 | ||
4031 | ------------------------------------------------- | |
b1889c36 | 4032 | $ git merge-base <commit1> <commit2> |
b181d57f BF |
4033 | ------------------------------------------------- |
4034 | ||
4035 | which will return you the commit they are both based on. You should | |
4036 | now look up the "tree" objects of those commits, which you can easily | |
4037 | do with (for example) | |
4038 | ||
4039 | ------------------------------------------------- | |
b1889c36 | 4040 | $ git cat-file commit <commitname> | head -1 |
b181d57f BF |
4041 | ------------------------------------------------- |
4042 | ||
4043 | since the tree object information is always the first line in a commit | |
4044 | object. | |
4045 | ||
1191ee18 | 4046 | Once you know the three trees you are going to merge (the one "original" |
c64415e2 | 4047 | tree, aka the common tree, and the two "result" trees, aka the branches |
1191ee18 BF |
4048 | you want to merge), you do a "merge" read into the index. This will |
4049 | complain if it has to throw away your old index contents, so you should | |
2ef8ac1b | 4050 | make sure that you've committed those--in fact you would normally |
1191ee18 BF |
4051 | always do a merge against your last commit (which should thus match what |
4052 | you have in your current index anyway). | |
b181d57f BF |
4053 | |
4054 | To do the merge, do | |
4055 | ||
4056 | ------------------------------------------------- | |
b1889c36 | 4057 | $ git read-tree -m -u <origtree> <yourtree> <targettree> |
b181d57f BF |
4058 | ------------------------------------------------- |
4059 | ||
4060 | which will do all trivial merge operations for you directly in the | |
4061 | index file, and you can just write the result out with | |
467c0197 | 4062 | `git write-tree`. |
b181d57f BF |
4063 | |
4064 | ||
e34caace | 4065 | [[merging-multiple-trees-2]] |
b181d57f BF |
4066 | Merging multiple trees, continued |
4067 | --------------------------------- | |
4068 | ||
4069 | Sadly, many merges aren't trivial. If there are files that have | |
06ada152 | 4070 | been added, moved or removed, or if both branches have modified the |
b181d57f BF |
4071 | same file, you will be left with an index tree that contains "merge |
4072 | entries" in it. Such an index tree can 'NOT' be written out to a tree | |
4073 | object, and you will have to resolve any such merge clashes using | |
4074 | other tools before you can write out the result. | |
4075 | ||
b1889c36 | 4076 | You can examine such index state with `git ls-files --unmerged` |
b181d57f BF |
4077 | command. An example: |
4078 | ||
4079 | ------------------------------------------------ | |
b1889c36 JN |
4080 | $ git read-tree -m $orig HEAD $target |
4081 | $ git ls-files --unmerged | |
b181d57f BF |
4082 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c |
4083 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c | |
4084 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c | |
4085 | ------------------------------------------------ | |
4086 | ||
b1889c36 | 4087 | Each line of the `git ls-files --unmerged` output begins with |
a6e5ef7d | 4088 | the blob mode bits, blob SHA-1, 'stage number', and the |
2de9b711 | 4089 | filename. The 'stage number' is Git's way to say which tree it |
edfbbf7e ŠN |
4090 | came from: stage 1 corresponds to the `$orig` tree, stage 2 to |
4091 | the `HEAD` tree, and stage 3 to the `$target` tree. | |
b181d57f BF |
4092 | |
4093 | Earlier we said that trivial merges are done inside | |
6127c086 | 4094 | `git read-tree -m`. For example, if the file did not change |
b181d57f BF |
4095 | from `$orig` to `HEAD` nor `$target`, or if the file changed |
4096 | from `$orig` to `HEAD` and `$orig` to `$target` the same way, | |
4097 | obviously the final outcome is what is in `HEAD`. What the | |
4098 | above example shows is that file `hello.c` was changed from | |
4099 | `$orig` to `HEAD` and `$orig` to `$target` in a different way. | |
4100 | You could resolve this by running your favorite 3-way merge | |
2de9b711 | 4101 | program, e.g. `diff3`, `merge`, or Git's own merge-file, on |
c64415e2 | 4102 | the blob objects from these three stages yourself, like this: |
b181d57f BF |
4103 | |
4104 | ------------------------------------------------ | |
b1889c36 JN |
4105 | $ git cat-file blob 263414f... >hello.c~1 |
4106 | $ git cat-file blob 06fa6a2... >hello.c~2 | |
4107 | $ git cat-file blob cc44c73... >hello.c~3 | |
c64415e2 | 4108 | $ git merge-file hello.c~2 hello.c~1 hello.c~3 |
b181d57f BF |
4109 | ------------------------------------------------ |
4110 | ||
4111 | This would leave the merge result in `hello.c~2` file, along | |
4112 | with conflict markers if there are conflicts. After verifying | |
2de9b711 | 4113 | the merge result makes sense, you can tell Git what the final |
b181d57f BF |
4114 | merge result for this file is by: |
4115 | ||
4116 | ------------------------------------------------- | |
4117 | $ mv -f hello.c~2 hello.c | |
b1889c36 | 4118 | $ git update-index hello.c |
b181d57f BF |
4119 | ------------------------------------------------- |
4120 | ||
6127c086 | 4121 | When a path is in the "unmerged" state, running `git update-index` for |
2de9b711 | 4122 | that path tells Git to mark the path resolved. |
b181d57f | 4123 | |
2de9b711 | 4124 | The above is the description of a Git merge at the lowest level, |
b181d57f | 4125 | to help you understand what conceptually happens under the hood. |
2de9b711 | 4126 | In practice, nobody, not even Git itself, runs `git cat-file` three times |
6127c086 | 4127 | for this. There is a `git merge-index` program that extracts the |
b181d57f BF |
4128 | stages to temporary files and calls a "merge" script on it: |
4129 | ||
4130 | ------------------------------------------------- | |
b1889c36 | 4131 | $ git merge-index git-merge-one-file hello.c |
b181d57f BF |
4132 | ------------------------------------------------- |
4133 | ||
6127c086 | 4134 | and that is what higher level `git merge -s resolve` is implemented with. |
b181d57f | 4135 | |
971aa71f | 4136 | [[hacking-git]] |
2de9b711 | 4137 | Hacking Git |
971aa71f BF |
4138 | =========== |
4139 | ||
2de9b711 TA |
4140 | This chapter covers internal details of the Git implementation which |
4141 | probably only Git developers need to understand. | |
971aa71f | 4142 | |
f2327c6c BF |
4143 | [[object-details]] |
4144 | Object storage format | |
4145 | --------------------- | |
4146 | ||
4147 | All objects have a statically determined "type" which identifies the | |
4148 | format of the object (i.e. how it is used, and how it can refer to other | |
4149 | objects). There are currently four different object types: "blob", | |
4150 | "tree", "commit", and "tag". | |
4151 | ||
4152 | Regardless of object type, all objects share the following | |
4153 | characteristics: they are all deflated with zlib, and have a header | |
4154 | that not only specifies their type, but also provides size information | |
a6e5ef7d | 4155 | about the data in the object. It's worth noting that the SHA-1 hash |
f2327c6c BF |
4156 | that is used to name the object is the hash of the original data |
4157 | plus this header, so `sha1sum` 'file' does not match the object name | |
4158 | for 'file'. | |
2de9b711 | 4159 | (Historical note: in the dawn of the age of Git the hash |
a6e5ef7d | 4160 | was the SHA-1 of the 'compressed' object.) |
f2327c6c BF |
4161 | |
4162 | As a result, the general consistency of an object can always be tested | |
4163 | independently of the contents or the type of the object: all objects can | |
4164 | be validated by verifying that (a) their hashes match the content of the | |
4165 | file and (b) the object successfully inflates to a stream of bytes that | |
1249d8ad TK |
4166 | forms a sequence of |
4167 | `<ascii type without space> + <space> + <ascii decimal size> + | |
4168 | <byte\0> + <binary object data>`. | |
f2327c6c BF |
4169 | |
4170 | The structured objects can further have their structure and | |
4171 | connectivity to other objects verified. This is generally done with | |
6127c086 | 4172 | the `git fsck` program, which generates a full dependency graph |
f2327c6c BF |
4173 | of all objects, and verifies their internal consistency (in addition |
4174 | to just verifying their superficial consistency through the hash). | |
4175 | ||
126640af | 4176 | [[birdview-on-the-source-code]] |
a5fc33b4 BF |
4177 | A birds-eye view of Git's source code |
4178 | ------------------------------------- | |
126640af | 4179 | |
a5fc33b4 BF |
4180 | It is not always easy for new developers to find their way through Git's |
4181 | source code. This section gives you a little guidance to show where to | |
4182 | start. | |
126640af | 4183 | |
a5fc33b4 | 4184 | A good place to start is with the contents of the initial commit, with: |
126640af JS |
4185 | |
4186 | ---------------------------------------------------- | |
a5fc33b4 | 4187 | $ git checkout e83c5163 |
126640af JS |
4188 | ---------------------------------------------------- |
4189 | ||
2de9b711 | 4190 | The initial revision lays the foundation for almost everything Git has |
a5fc33b4 | 4191 | today, but is small enough to read in one sitting. |
126640af | 4192 | |
a5fc33b4 BF |
4193 | Note that terminology has changed since that revision. For example, the |
4194 | README in that revision uses the word "changeset" to describe what we | |
4195 | now call a <<def_commit_object,commit>>. | |
126640af | 4196 | |
843c81dc | 4197 | Also, we do not call it "cache" any more, but rather "index"; however, the |
126640af JS |
4198 | file is still called `cache.h`. Remark: Not much reason to change it now, |
4199 | especially since there is no good single name for it anyway, because it is | |
4200 | basically _the_ header file which is included by _all_ of Git's C sources. | |
4201 | ||
a5fc33b4 BF |
4202 | If you grasp the ideas in that initial commit, you should check out a |
4203 | more recent version and skim `cache.h`, `object.h` and `commit.h`. | |
126640af JS |
4204 | |
4205 | In the early days, Git (in the tradition of UNIX) was a bunch of programs | |
4206 | which were extremely simple, and which you used in scripts, piping the | |
4207 | output of one into another. This turned out to be good for initial | |
4208 | development, since it was easier to test new things. However, recently | |
4209 | many of these parts have become builtins, and some of the core has been | |
4210 | "libified", i.e. put into libgit.a for performance, portability reasons, | |
4211 | and to avoid code duplication. | |
4212 | ||
4213 | By now, you know what the index is (and find the corresponding data | |
4214 | structures in `cache.h`), and that there are just a couple of object types | |
4215 | (blobs, trees, commits and tags) which inherit their common structure from | |
4216 | `struct object`, which is their first member (and thus, you can cast e.g. | |
4217 | `(struct object *)commit` to achieve the _same_ as `&commit->object`, i.e. | |
4218 | get at the object name and flags). | |
4219 | ||
4220 | Now is a good point to take a break to let this information sink in. | |
4221 | ||
4222 | Next step: get familiar with the object naming. Read <<naming-commits>>. | |
4223 | There are quite a few ways to name an object (and not only revisions!). | |
4224 | All of these are handled in `sha1_name.c`. Just have a quick look at | |
4225 | the function `get_sha1()`. A lot of the special handling is done by | |
4226 | functions like `get_sha1_basic()` or the likes. | |
4227 | ||
4228 | This is just to get you into the groove for the most libified part of Git: | |
4229 | the revision walker. | |
4230 | ||
6127c086 | 4231 | Basically, the initial version of `git log` was a shell script: |
126640af JS |
4232 | |
4233 | ---------------------------------------------------------------- | |
4234 | $ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ | |
4235 | LESS=-S ${PAGER:-less} | |
4236 | ---------------------------------------------------------------- | |
4237 | ||
4238 | What does this mean? | |
4239 | ||
6127c086 | 4240 | `git rev-list` is the original version of the revision walker, which |
126640af | 4241 | _always_ printed a list of revisions to stdout. It is still functional, |
57f6ec02 | 4242 | and needs to, since most new Git commands start out as scripts using |
6127c086 | 4243 | `git rev-list`. |
126640af | 4244 | |
6127c086 | 4245 | `git rev-parse` is not as important any more; it was only used to filter out |
126640af JS |
4246 | options that were relevant for the different plumbing commands that were |
4247 | called by the script. | |
4248 | ||
6127c086 | 4249 | Most of what `git rev-list` did is contained in `revision.c` and |
126640af JS |
4250 | `revision.h`. It wraps the options in a struct named `rev_info`, which |
4251 | controls how and what revisions are walked, and more. | |
4252 | ||
6127c086 | 4253 | The original job of `git rev-parse` is now taken by the function |
126640af JS |
4254 | `setup_revisions()`, which parses the revisions and the common command line |
4255 | options for the revision walker. This information is stored in the struct | |
4256 | `rev_info` for later consumption. You can do your own command line option | |
4257 | parsing after calling `setup_revisions()`. After that, you have to call | |
4258 | `prepare_revision_walk()` for initialization, and then you can get the | |
4259 | commits one by one with the function `get_revision()`. | |
4260 | ||
4261 | If you are interested in more details of the revision walking process, | |
4262 | just have a look at the first implementation of `cmd_log()`; call | |
6cf378f0 | 4263 | `git show v1.3.0~155^2~4` and scroll down to that function (note that you |
126640af JS |
4264 | no longer need to call `setup_pager()` directly). |
4265 | ||
6127c086 | 4266 | Nowadays, `git log` is a builtin, which means that it is _contained_ in the |
126640af JS |
4267 | command `git`. The source side of a builtin is |
4268 | ||
09b7e220 PH |
4269 | - a function called `cmd_<bla>`, typically defined in `builtin/<bla.c>` |
4270 | (note that older versions of Git used to have it in `builtin-<bla>.c` | |
4271 | instead), and declared in `builtin.h`. | |
126640af JS |
4272 | |
4273 | - an entry in the `commands[]` array in `git.c`, and | |
4274 | ||
4275 | - an entry in `BUILTIN_OBJECTS` in the `Makefile`. | |
4276 | ||
4277 | Sometimes, more than one builtin is contained in one source file. For | |
09b7e220 | 4278 | example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin/log.c`, |
126640af JS |
4279 | since they share quite a bit of code. In that case, the commands which are |
4280 | _not_ named like the `.c` file in which they live have to be listed in | |
4281 | `BUILT_INS` in the `Makefile`. | |
4282 | ||
6127c086 | 4283 | `git log` looks more complicated in C than it does in the original script, |
126640af JS |
4284 | but that allows for a much greater flexibility and performance. |
4285 | ||
4286 | Here again it is a good point to take a pause. | |
4287 | ||
4288 | Lesson three is: study the code. Really, it is the best way to learn about | |
4289 | the organization of Git (after you know the basic concepts). | |
4290 | ||
4291 | So, think about something which you are interested in, say, "how can I | |
4292 | access a blob just knowing the object name of it?". The first step is to | |
4293 | find a Git command with which you can do it. In this example, it is either | |
6127c086 | 4294 | `git show` or `git cat-file`. |
126640af | 4295 | |
6127c086 | 4296 | For the sake of clarity, let's stay with `git cat-file`, because it |
126640af JS |
4297 | |
4298 | - is plumbing, and | |
4299 | ||
4300 | - was around even in the initial commit (it literally went only through | |
09b7e220 | 4301 | some 20 revisions as `cat-file.c`, was renamed to `builtin/cat-file.c` |
126640af JS |
4302 | when made a builtin, and then saw less than 10 versions). |
4303 | ||
09b7e220 | 4304 | So, look into `builtin/cat-file.c`, search for `cmd_cat_file()` and look what |
126640af JS |
4305 | it does. |
4306 | ||
4307 | ------------------------------------------------------------------ | |
4308 | git_config(git_default_config); | |
4309 | if (argc != 3) | |
6127c086 | 4310 | usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>"); |
126640af JS |
4311 | if (get_sha1(argv[2], sha1)) |
4312 | die("Not a valid object name %s", argv[2]); | |
4313 | ------------------------------------------------------------------ | |
4314 | ||
4315 | Let's skip over the obvious details; the only really interesting part | |
4316 | here is the call to `get_sha1()`. It tries to interpret `argv[2]` as an | |
4317 | object name, and if it refers to an object which is present in the current | |
4318 | repository, it writes the resulting SHA-1 into the variable `sha1`. | |
4319 | ||
4320 | Two things are interesting here: | |
4321 | ||
4322 | - `get_sha1()` returns 0 on _success_. This might surprise some new | |
4323 | Git hackers, but there is a long tradition in UNIX to return different | |
2ef8ac1b | 4324 | negative numbers in case of different errors--and 0 on success. |
126640af JS |
4325 | |
4326 | - the variable `sha1` in the function signature of `get_sha1()` is `unsigned | |
6cf378f0 | 4327 | char *`, but is actually expected to be a pointer to `unsigned |
126640af | 4328 | char[20]`. This variable will contain the 160-bit SHA-1 of the given |
6cf378f0 | 4329 | commit. Note that whenever a SHA-1 is passed as `unsigned char *`, it |
126640af | 4330 | is the binary representation, as opposed to the ASCII representation in |
a5fc33b4 | 4331 | hex characters, which is passed as `char *`. |
126640af JS |
4332 | |
4333 | You will see both of these things throughout the code. | |
4334 | ||
4335 | Now, for the meat: | |
4336 | ||
4337 | ----------------------------------------------------------------------------- | |
4338 | case 0: | |
4339 | buf = read_object_with_reference(sha1, argv[1], &size, NULL); | |
4340 | ----------------------------------------------------------------------------- | |
4341 | ||
4342 | This is how you read a blob (actually, not only a blob, but any type of | |
4343 | object). To know how the function `read_object_with_reference()` actually | |
4344 | works, find the source code for it (something like `git grep | |
2de9b711 | 4345 | read_object_with | grep ":[a-z]"` in the Git repository), and read |
126640af JS |
4346 | the source. |
4347 | ||
4348 | To find out how the result can be used, just read on in `cmd_cat_file()`: | |
4349 | ||
4350 | ----------------------------------- | |
4351 | write_or_die(1, buf, size); | |
4352 | ----------------------------------- | |
4353 | ||
4354 | Sometimes, you do not know where to look for a feature. In many such cases, | |
6127c086 | 4355 | it helps to search through the output of `git log`, and then `git show` the |
126640af JS |
4356 | corresponding commit. |
4357 | ||
6127c086 | 4358 | Example: If you know that there was some test case for `git bundle`, but |
126640af JS |
4359 | do not remember where it was (yes, you _could_ `git grep bundle t/`, but that |
4360 | does not illustrate the point!): | |
4361 | ||
4362 | ------------------------ | |
4363 | $ git log --no-merges t/ | |
4364 | ------------------------ | |
4365 | ||
4366 | In the pager (`less`), just search for "bundle", go a few lines back, | |
4367 | and see that it is in commit 18449ab0... Now just copy this object name, | |
4368 | and paste it into the command line | |
4369 | ||
4370 | ------------------- | |
4371 | $ git show 18449ab0 | |
4372 | ------------------- | |
4373 | ||
4374 | Voila. | |
4375 | ||
4376 | Another example: Find out what to do in order to make some script a | |
4377 | builtin: | |
4378 | ||
4379 | ------------------------------------------------- | |
09b7e220 | 4380 | $ git log --no-merges --diff-filter=A builtin/*.c |
126640af JS |
4381 | ------------------------------------------------- |
4382 | ||
4383 | You see, Git is actually the best tool to find out about the source of Git | |
4384 | itself! | |
4385 | ||
e34caace | 4386 | [[glossary]] |
73a1d050 | 4387 | Git Glossary |
497c8331 CC |
4388 | ============ |
4389 | ||
4390 | include::glossary-content.txt[] | |
d19fbc3c | 4391 | |
2624d9a5 | 4392 | [[git-quick-start]] |
99f171bb BF |
4393 | Appendix A: Git Quick Reference |
4394 | =============================== | |
2624d9a5 | 4395 | |
99f171bb BF |
4396 | This is a quick summary of the major commands; the previous chapters |
4397 | explain how these work in more detail. | |
2624d9a5 BF |
4398 | |
4399 | [[quick-creating-a-new-repository]] | |
4400 | Creating a new repository | |
4401 | ------------------------- | |
4402 | ||
4403 | From a tarball: | |
4404 | ||
4405 | ----------------------------------------------- | |
4406 | $ tar xzf project.tar.gz | |
4407 | $ cd project | |
4408 | $ git init | |
4409 | Initialized empty Git repository in .git/ | |
4410 | $ git add . | |
4411 | $ git commit | |
4412 | ----------------------------------------------- | |
4413 | ||
4414 | From a remote repository: | |
4415 | ||
4416 | ----------------------------------------------- | |
4417 | $ git clone git://example.com/pub/project.git | |
4418 | $ cd project | |
4419 | ----------------------------------------------- | |
4420 | ||
4421 | [[managing-branches]] | |
4422 | Managing branches | |
4423 | ----------------- | |
4424 | ||
4425 | ----------------------------------------------- | |
4426 | $ git branch # list all local branches in this repo | |
4427 | $ git checkout test # switch working directory to branch "test" | |
4428 | $ git branch new # create branch "new" starting at current HEAD | |
4429 | $ git branch -d new # delete branch "new" | |
4430 | ----------------------------------------------- | |
4431 | ||
06ada152 | 4432 | Instead of basing a new branch on current HEAD (the default), use: |
2624d9a5 BF |
4433 | |
4434 | ----------------------------------------------- | |
4435 | $ git branch new test # branch named "test" | |
4436 | $ git branch new v2.6.15 # tag named v2.6.15 | |
4437 | $ git branch new HEAD^ # commit before the most recent | |
4438 | $ git branch new HEAD^^ # commit before that | |
4439 | $ git branch new test~10 # ten commits before tip of branch "test" | |
4440 | ----------------------------------------------- | |
4441 | ||
4442 | Create and switch to a new branch at the same time: | |
4443 | ||
4444 | ----------------------------------------------- | |
4445 | $ git checkout -b new v2.6.15 | |
4446 | ----------------------------------------------- | |
4447 | ||
4448 | Update and examine branches from the repository you cloned from: | |
4449 | ||
4450 | ----------------------------------------------- | |
4451 | $ git fetch # update | |
4452 | $ git branch -r # list | |
4453 | origin/master | |
4454 | origin/next | |
4455 | ... | |
4456 | $ git checkout -b masterwork origin/master | |
4457 | ----------------------------------------------- | |
4458 | ||
4459 | Fetch a branch from a different repository, and give it a new | |
4460 | name in your repository: | |
4461 | ||
4462 | ----------------------------------------------- | |
4463 | $ git fetch git://example.com/project.git theirbranch:mybranch | |
4464 | $ git fetch git://example.com/project.git v2.6.15:mybranch | |
4465 | ----------------------------------------------- | |
4466 | ||
4467 | Keep a list of repositories you work with regularly: | |
4468 | ||
4469 | ----------------------------------------------- | |
4470 | $ git remote add example git://example.com/project.git | |
4471 | $ git remote # list remote repositories | |
4472 | example | |
4473 | origin | |
4474 | $ git remote show example # get details | |
4475 | * remote example | |
4476 | URL: git://example.com/project.git | |
4477 | Tracked remote branches | |
20244ea2 JS |
4478 | master |
4479 | next | |
4480 | ... | |
2624d9a5 BF |
4481 | $ git fetch example # update branches from example |
4482 | $ git branch -r # list all remote branches | |
4483 | ----------------------------------------------- | |
4484 | ||
4485 | ||
4486 | [[exploring-history]] | |
4487 | Exploring history | |
4488 | ----------------- | |
4489 | ||
4490 | ----------------------------------------------- | |
4491 | $ gitk # visualize and browse history | |
4492 | $ git log # list all commits | |
4493 | $ git log src/ # ...modifying src/ | |
4494 | $ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15 | |
4495 | $ git log master..test # ...in branch test, not in branch master | |
4496 | $ git log test..master # ...in branch master, but not in test | |
4497 | $ git log test...master # ...in one branch, not in both | |
4498 | $ git log -S'foo()' # ...where difference contain "foo()" | |
4499 | $ git log --since="2 weeks ago" | |
4500 | $ git log -p # show patches as well | |
4501 | $ git show # most recent commit | |
4502 | $ git diff v2.6.15..v2.6.16 # diff between two tagged versions | |
4503 | $ git diff v2.6.15..HEAD # diff with current head | |
4504 | $ git grep "foo()" # search working directory for "foo()" | |
4505 | $ git grep v2.6.15 "foo()" # search old tree for "foo()" | |
4506 | $ git show v2.6.15:a.txt # look at old version of a.txt | |
4507 | ----------------------------------------------- | |
4508 | ||
4509 | Search for regressions: | |
4510 | ||
4511 | ----------------------------------------------- | |
4512 | $ git bisect start | |
4513 | $ git bisect bad # current version is bad | |
4514 | $ git bisect good v2.6.13-rc2 # last known good revision | |
4515 | Bisecting: 675 revisions left to test after this | |
4516 | # test here, then: | |
4517 | $ git bisect good # if this revision is good, or | |
4518 | $ git bisect bad # if this revision is bad. | |
4519 | # repeat until done. | |
4520 | ----------------------------------------------- | |
4521 | ||
4522 | [[making-changes]] | |
4523 | Making changes | |
4524 | -------------- | |
4525 | ||
2de9b711 | 4526 | Make sure Git knows who to blame: |
2624d9a5 BF |
4527 | |
4528 | ------------------------------------------------ | |
4529 | $ cat >>~/.gitconfig <<\EOF | |
4530 | [user] | |
4531 | name = Your Name Comes Here | |
4532 | email = you@yourdomain.example.com | |
4533 | EOF | |
4534 | ------------------------------------------------ | |
4535 | ||
4536 | Select file contents to include in the next commit, then make the | |
4537 | commit: | |
4538 | ||
4539 | ----------------------------------------------- | |
4540 | $ git add a.txt # updated file | |
4541 | $ git add b.txt # new file | |
4542 | $ git rm c.txt # old file | |
4543 | $ git commit | |
4544 | ----------------------------------------------- | |
4545 | ||
4546 | Or, prepare and create the commit in one step: | |
4547 | ||
4548 | ----------------------------------------------- | |
4549 | $ git commit d.txt # use latest content only of d.txt | |
4550 | $ git commit -a # use latest content of all tracked files | |
4551 | ----------------------------------------------- | |
4552 | ||
4553 | [[merging]] | |
4554 | Merging | |
4555 | ------- | |
4556 | ||
4557 | ----------------------------------------------- | |
4558 | $ git merge test # merge branch "test" into the current branch | |
4559 | $ git pull git://example.com/project.git master | |
4560 | # fetch and merge in remote branch | |
4561 | $ git pull . test # equivalent to git merge test | |
4562 | ----------------------------------------------- | |
4563 | ||
4564 | [[sharing-your-changes]] | |
4565 | Sharing your changes | |
4566 | -------------------- | |
4567 | ||
4568 | Importing or exporting patches: | |
4569 | ||
4570 | ----------------------------------------------- | |
4571 | $ git format-patch origin..HEAD # format a patch for each commit | |
4572 | # in HEAD but not in origin | |
4573 | $ git am mbox # import patches from the mailbox "mbox" | |
4574 | ----------------------------------------------- | |
4575 | ||
2de9b711 | 4576 | Fetch a branch in a different Git repository, then merge into the |
2624d9a5 BF |
4577 | current branch: |
4578 | ||
4579 | ----------------------------------------------- | |
4580 | $ git pull git://example.com/project.git theirbranch | |
4581 | ----------------------------------------------- | |
4582 | ||
4583 | Store the fetched branch into a local branch before merging into the | |
4584 | current branch: | |
4585 | ||
4586 | ----------------------------------------------- | |
4587 | $ git pull git://example.com/project.git theirbranch:mybranch | |
4588 | ----------------------------------------------- | |
4589 | ||
4590 | After creating commits on a local branch, update the remote | |
4591 | branch with your commits: | |
4592 | ||
4593 | ----------------------------------------------- | |
4594 | $ git push ssh://example.com/project.git mybranch:theirbranch | |
4595 | ----------------------------------------------- | |
4596 | ||
4597 | When remote and local branch are both named "test": | |
4598 | ||
4599 | ----------------------------------------------- | |
4600 | $ git push ssh://example.com/project.git test | |
4601 | ----------------------------------------------- | |
4602 | ||
4603 | Shortcut version for a frequently used remote repository: | |
4604 | ||
4605 | ----------------------------------------------- | |
4606 | $ git remote add example ssh://example.com/project.git | |
4607 | $ git push example test | |
4608 | ----------------------------------------------- | |
4609 | ||
4610 | [[repository-maintenance]] | |
4611 | Repository maintenance | |
4612 | ---------------------- | |
4613 | ||
4614 | Check for corruption: | |
4615 | ||
4616 | ----------------------------------------------- | |
4617 | $ git fsck | |
4618 | ----------------------------------------------- | |
4619 | ||
4620 | Recompress, remove unused cruft: | |
4621 | ||
4622 | ----------------------------------------------- | |
4623 | $ git gc | |
4624 | ----------------------------------------------- | |
4625 | ||
4626 | ||
e34caace | 4627 | [[todo]] |
2624d9a5 BF |
4628 | Appendix B: Notes and todo list for this manual |
4629 | =============================================== | |
6bd9b682 BF |
4630 | |
4631 | This is a work in progress. | |
4632 | ||
4633 | The basic requirements: | |
ecd95b53 BF |
4634 | |
4635 | - It must be readable in order, from beginning to end, by someone | |
4636 | intelligent with a basic grasp of the UNIX command line, but without | |
2de9b711 | 4637 | any special knowledge of Git. If necessary, any other prerequisites |
ecd95b53 BF |
4638 | should be specifically mentioned as they arise. |
4639 | - Whenever possible, section headings should clearly describe the task | |
4640 | they explain how to do, in language that requires no more knowledge | |
4641 | than necessary: for example, "importing patches into a project" rather | |
6127c086 | 4642 | than "the `git am` command" |
6bd9b682 | 4643 | |
d5cd5de4 BF |
4644 | Think about how to create a clear chapter dependency graph that will |
4645 | allow people to get to important topics without necessarily reading | |
4646 | everything in between. | |
d19fbc3c | 4647 | |
1249d8ad | 4648 | Scan `Documentation/` for other stuff left out; in particular: |
ecd95b53 BF |
4649 | |
4650 | - howto's | |
1249d8ad | 4651 | - some of `technical/`? |
ecd95b53 | 4652 | - hooks |
5162e697 | 4653 | - list of commands in linkgit:git[1] |
d19fbc3c BF |
4654 | |
4655 | Scan email archives for other stuff left out | |
4656 | ||
4657 | Scan man pages to see if any assume more background than this manual | |
4658 | provides. | |
4659 | ||
2f99710c | 4660 | Simplify beginning by suggesting disconnected head instead of |
b181d57f | 4661 | temporary branch creation? |
d19fbc3c | 4662 | |
2f99710c BF |
4663 | Add more good examples. Entire sections of just cookbook examples |
4664 | might be a good idea; maybe make an "advanced examples" section a | |
4665 | standard end-of-chapter section? | |
d19fbc3c BF |
4666 | |
4667 | Include cross-references to the glossary, where appropriate. | |
4668 | ||
9a241220 BF |
4669 | Document shallow clones? See draft 1.5.0 release notes for some |
4670 | documentation. | |
4671 | ||
3dff5379 | 4672 | Add a section on working with other version control systems, including |
9a241220 BF |
4673 | CVS, Subversion, and just imports of series of release tarballs. |
4674 | ||
a8cd1402 | 4675 | More details on gitweb? |
0b375ab0 BF |
4676 | |
4677 | Write a chapter on using plumbing and writing scripts. | |
d9bd321c BF |
4678 | |
4679 | Alternates, clone -reference, etc. | |
4680 | ||
1cdade2c | 4681 | More on recovery from repository corruption. See: |
efe6de6e OB |
4682 | http://marc.info/?l=git&m=117263864820799&w=2 |
4683 | http://marc.info/?l=git&m=117147855503798&w=2 |