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333d7d37 | 1 | Git User Manual |
145e073b | 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 | 221 | command; running gitk now on a Git repository and looking for merge |
ddd4ddef | 222 | commits will help understand how 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`:: |
df47da75 | 271 | list all branches. |
1249d8ad TK |
272 | `git branch <branch>`:: |
273 | create a new branch named `<branch>`, referencing the same | |
df47da75 | 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, | |
df47da75 | 278 | including using a branch name or a tag name. |
1249d8ad | 279 | `git branch -d <branch>`:: |
df47da75 TA |
280 | delete the branch `<branch>`; if the branch is not fully |
281 | merged in its upstream branch or contained in the current branch, | |
282 | this command will fail with a warning. | |
1249d8ad | 283 | `git branch -D <branch>`:: |
df47da75 | 284 | delete the branch `<branch>` irrespective of its merged status. |
1249d8ad TK |
285 | `git checkout <branch>`:: |
286 | make the current branch `<branch>`, updating the working | |
df47da75 | 287 | directory to reflect the version referenced by `<branch>`. |
1249d8ad TK |
288 | `git checkout -b <new> <start-point>`:: |
289 | create a new branch `<new>` referencing `<start-point>`, and | |
d19fbc3c BF |
290 | check it out. |
291 | ||
72a76c95 | 292 | The special symbol "HEAD" can always be used to refer to the current |
1249d8ad TK |
293 | branch. In fact, Git uses a file named `HEAD` in the `.git` directory |
294 | to remember which branch is current: | |
72a76c95 BF |
295 | |
296 | ------------------------------------------------ | |
297 | $ cat .git/HEAD | |
298 | ref: refs/heads/master | |
299 | ------------------------------------------------ | |
300 | ||
25d9f3fa | 301 | [[detached-head]] |
72a76c95 BF |
302 | Examining an old version without creating a new branch |
303 | ------------------------------------------------------ | |
304 | ||
6127c086 | 305 | The `git checkout` command normally expects a branch head, but will also |
72a76c95 BF |
306 | accept an arbitrary commit; for example, you can check out the commit |
307 | referenced by a tag: | |
308 | ||
309 | ------------------------------------------------ | |
310 | $ git checkout v2.6.17 | |
95f9be55 TA |
311 | Note: checking out 'v2.6.17'. |
312 | ||
313 | You are in 'detached HEAD' state. You can look around, make experimental | |
314 | changes and commit them, and you can discard any commits you make in this | |
315 | state without impacting any branches by performing another checkout. | |
316 | ||
317 | If you want to create a new branch to retain commits you create, you may | |
318 | do so (now or later) by using -b with the checkout command again. Example: | |
319 | ||
320 | git checkout -b new_branch_name | |
321 | ||
72a76c95 BF |
322 | HEAD is now at 427abfa... Linux v2.6.17 |
323 | ------------------------------------------------ | |
324 | ||
a6e5ef7d | 325 | The HEAD then refers to the SHA-1 of the commit instead of to a branch, |
72a76c95 BF |
326 | and git branch shows that you are no longer on a branch: |
327 | ||
328 | ------------------------------------------------ | |
329 | $ cat .git/HEAD | |
330 | 427abfa28afedffadfca9dd8b067eb6d36bac53f | |
953f3d6f | 331 | $ git branch |
95f9be55 | 332 | * (detached from v2.6.17) |
72a76c95 BF |
333 | master |
334 | ------------------------------------------------ | |
335 | ||
336 | In this case we say that the HEAD is "detached". | |
337 | ||
953f3d6f BF |
338 | This is an easy way to check out a particular version without having to |
339 | make up a name for the new branch. You can still create a new branch | |
340 | (or tag) for this version later if you decide to. | |
d19fbc3c | 341 | |
e34caace | 342 | [[examining-remote-branches]] |
d19fbc3c BF |
343 | Examining branches from a remote repository |
344 | ------------------------------------------- | |
345 | ||
346 | The "master" branch that was created at the time you cloned is a copy | |
347 | of the HEAD in the repository that you cloned from. That repository | |
348 | may also have had other branches, though, and your local repository | |
66a062a1 MM |
349 | keeps branches which track each of those remote branches, called |
350 | remote-tracking branches, which you | |
1249d8ad | 351 | can view using the `-r` option to linkgit:git-branch[1]: |
d19fbc3c BF |
352 | |
353 | ------------------------------------------------ | |
354 | $ git branch -r | |
355 | origin/HEAD | |
356 | origin/html | |
357 | origin/maint | |
358 | origin/man | |
359 | origin/master | |
360 | origin/next | |
361 | origin/pu | |
362 | origin/todo | |
363 | ------------------------------------------------ | |
364 | ||
66a062a1 MM |
365 | In this example, "origin" is called a remote repository, or "remote" |
366 | for short. The branches of this repository are called "remote | |
367 | branches" from our point of view. The remote-tracking branches listed | |
368 | above were created based on the remote branches at clone time and will | |
1249d8ad | 369 | be updated by `git fetch` (hence `git pull`) and `git push`. See |
66a062a1 MM |
370 | <<Updating-a-repository-With-git-fetch>> for details. |
371 | ||
45dfd403 JN |
372 | You might want to build on one of these remote-tracking branches |
373 | on a branch of your own, just as you would for a tag: | |
d19fbc3c BF |
374 | |
375 | ------------------------------------------------ | |
376 | $ git checkout -b my-todo-copy origin/todo | |
377 | ------------------------------------------------ | |
378 | ||
1249d8ad | 379 | You can also check out `origin/todo` directly to examine it or |
45dfd403 JN |
380 | write a one-off patch. See <<detached-head,detached head>>. |
381 | ||
2de9b711 | 382 | Note that the name "origin" is just the name that Git uses by default |
d19fbc3c BF |
383 | to refer to the repository that you cloned from. |
384 | ||
385 | [[how-git-stores-references]] | |
f60b9642 BF |
386 | Naming branches, tags, and other references |
387 | ------------------------------------------- | |
d19fbc3c BF |
388 | |
389 | Branches, remote-tracking branches, and tags are all references to | |
f60b9642 | 390 | commits. All references are named with a slash-separated path name |
1249d8ad | 391 | starting with `refs`; the names we've been using so far are actually |
f60b9642 | 392 | shorthand: |
d19fbc3c | 393 | |
1249d8ad TK |
394 | - The branch `test` is short for `refs/heads/test`. |
395 | - The tag `v2.6.18` is short for `refs/tags/v2.6.18`. | |
396 | - `origin/master` is short for `refs/remotes/origin/master`. | |
d19fbc3c | 397 | |
f60b9642 BF |
398 | The full name is occasionally useful if, for example, there ever |
399 | exists a tag and a branch with the same name. | |
d19fbc3c | 400 | |
1249d8ad | 401 | (Newly created refs are actually stored in the `.git/refs` directory, |
fc74ecc1 BF |
402 | under the path given by their name. However, for efficiency reasons |
403 | they may also be packed together in a single file; see | |
5162e697 | 404 | linkgit:git-pack-refs[1]). |
fc74ecc1 | 405 | |
c64415e2 BF |
406 | As another useful shortcut, the "HEAD" of a repository can be referred |
407 | to just using the name of that repository. So, for example, "origin" | |
408 | is usually a shortcut for the HEAD branch in the repository "origin". | |
d19fbc3c | 409 | |
2de9b711 | 410 | For the complete list of paths which Git checks for references, and |
f60b9642 BF |
411 | the order it uses to decide which to choose when there are multiple |
412 | references with the same shorthand name, see the "SPECIFYING | |
9d83e382 | 413 | REVISIONS" section of linkgit:gitrevisions[7]. |
d19fbc3c | 414 | |
aa971cb9 | 415 | [[Updating-a-repository-With-git-fetch]] |
6127c086 | 416 | Updating a repository with git fetch |
d19fbc3c BF |
417 | ------------------------------------ |
418 | ||
419 | Eventually the developer cloned from will do additional work in her | |
420 | repository, creating new commits and advancing the branches to point | |
421 | at the new commits. | |
422 | ||
1249d8ad | 423 | The command `git fetch`, with no arguments, will update all of the |
d19fbc3c BF |
424 | remote-tracking branches to the latest version found in her |
425 | repository. It will not touch any of your own branches--not even the | |
426 | "master" branch that was created for you on clone. | |
427 | ||
e34caace | 428 | [[fetching-branches]] |
d5cd5de4 BF |
429 | Fetching branches from other repositories |
430 | ----------------------------------------- | |
431 | ||
432 | You can also track branches from repositories other than the one you | |
5162e697 | 433 | cloned from, using linkgit:git-remote[1]: |
d5cd5de4 BF |
434 | |
435 | ------------------------------------------------- | |
34a25d4c TK |
436 | $ git remote add staging git://git.kernel.org/.../gregkh/staging.git |
437 | $ git fetch staging | |
438 | ... | |
439 | From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging | |
440 | * [new branch] master -> staging/master | |
441 | * [new branch] staging-linus -> staging/staging-linus | |
442 | * [new branch] staging-next -> staging/staging-next | |
d5cd5de4 BF |
443 | ------------------------------------------------- |
444 | ||
445 | New remote-tracking branches will be stored under the shorthand name | |
34a25d4c | 446 | that you gave `git remote add`, in this case `staging`: |
d5cd5de4 BF |
447 | |
448 | ------------------------------------------------- | |
449 | $ git branch -r | |
34a25d4c TK |
450 | origin/HEAD -> origin/master |
451 | origin/master | |
452 | staging/master | |
453 | staging/staging-linus | |
454 | staging/staging-next | |
d5cd5de4 BF |
455 | ------------------------------------------------- |
456 | ||
1249d8ad TK |
457 | If you run `git fetch <remote>` later, the remote-tracking branches |
458 | for the named `<remote>` will be updated. | |
d5cd5de4 | 459 | |
1249d8ad | 460 | If you examine the file `.git/config`, you will see that Git has added |
d5cd5de4 BF |
461 | a new stanza: |
462 | ||
463 | ------------------------------------------------- | |
464 | $ cat .git/config | |
465 | ... | |
34a25d4c TK |
466 | [remote "staging"] |
467 | url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git | |
468 | fetch = +refs/heads/*:refs/remotes/staging/* | |
d5cd5de4 BF |
469 | ... |
470 | ------------------------------------------------- | |
471 | ||
2de9b711 | 472 | This is what causes Git to track the remote's branches; you may modify |
1249d8ad | 473 | or delete these configuration options by editing `.git/config` with a |
fc90c536 | 474 | text editor. (See the "CONFIGURATION FILE" section of |
5162e697 | 475 | linkgit:git-config[1] for details.) |
d5cd5de4 | 476 | |
e34caace | 477 | [[exploring-git-history]] |
2de9b711 | 478 | Exploring Git history |
d19fbc3c BF |
479 | ===================== |
480 | ||
481 | Git is best thought of as a tool for storing the history of a | |
482 | collection of files. It does this by storing compressed snapshots of | |
1130845b | 483 | the contents of a file hierarchy, together with "commits" which show |
d19fbc3c BF |
484 | the relationships between these snapshots. |
485 | ||
486 | Git provides extremely flexible and fast tools for exploring the | |
487 | history of a project. | |
488 | ||
aacd404e | 489 | We start with one specialized tool that is useful for finding the |
d19fbc3c BF |
490 | commit that introduced a bug into a project. |
491 | ||
e34caace | 492 | [[using-bisect]] |
d19fbc3c BF |
493 | How to use bisect to find a regression |
494 | -------------------------------------- | |
495 | ||
496 | Suppose version 2.6.18 of your project worked, but the version at | |
497 | "master" crashes. Sometimes the best way to find the cause of such a | |
498 | regression is to perform a brute-force search through the project's | |
499 | history to find the particular commit that caused the problem. The | |
5162e697 | 500 | linkgit:git-bisect[1] command can help you do this: |
d19fbc3c BF |
501 | |
502 | ------------------------------------------------- | |
503 | $ git bisect start | |
504 | $ git bisect good v2.6.18 | |
505 | $ git bisect bad master | |
506 | Bisecting: 3537 revisions left to test after this | |
507 | [65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6] | |
508 | ------------------------------------------------- | |
509 | ||
1249d8ad | 510 | If you run `git branch` at this point, you'll see that Git has |
0e25790f CC |
511 | temporarily moved you in "(no branch)". HEAD is now detached from any |
512 | branch and points directly to a commit (with commit id 65934...) that | |
513 | is reachable from "master" but not from v2.6.18. Compile and test it, | |
514 | and see whether it crashes. Assume it does crash. Then: | |
d19fbc3c BF |
515 | |
516 | ------------------------------------------------- | |
517 | $ git bisect bad | |
518 | Bisecting: 1769 revisions left to test after this | |
519 | [7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings | |
520 | ------------------------------------------------- | |
521 | ||
2de9b711 | 522 | checks out an older version. Continue like this, telling Git at each |
d19fbc3c BF |
523 | stage whether the version it gives you is good or bad, and notice |
524 | that the number of revisions left to test is cut approximately in | |
525 | half each time. | |
526 | ||
527 | After about 13 tests (in this case), it will output the commit id of | |
528 | the guilty commit. You can then examine the commit with | |
5162e697 | 529 | linkgit:git-show[1], find out who wrote it, and mail them your bug |
d19fbc3c BF |
530 | report with the commit id. Finally, run |
531 | ||
532 | ------------------------------------------------- | |
533 | $ git bisect reset | |
534 | ------------------------------------------------- | |
535 | ||
0e25790f | 536 | to return you to the branch you were on before. |
d19fbc3c | 537 | |
6127c086 | 538 | Note that the version which `git bisect` checks out for you at each |
d19fbc3c BF |
539 | point is just a suggestion, and you're free to try a different |
540 | version if you think it would be a good idea. For example, | |
541 | occasionally you may land on a commit that broke something unrelated; | |
542 | run | |
543 | ||
544 | ------------------------------------------------- | |
04483524 | 545 | $ git bisect visualize |
d19fbc3c BF |
546 | ------------------------------------------------- |
547 | ||
548 | which will run gitk and label the commit it chose with a marker that | |
843c81dc | 549 | says "bisect". Choose a safe-looking commit nearby, note its commit |
d19fbc3c BF |
550 | id, and check it out with: |
551 | ||
552 | ------------------------------------------------- | |
553 | $ git reset --hard fb47ddb2db... | |
554 | ------------------------------------------------- | |
555 | ||
1249d8ad | 556 | then test, run `bisect good` or `bisect bad` as appropriate, and |
d19fbc3c BF |
557 | continue. |
558 | ||
1249d8ad TK |
559 | Instead of `git bisect visualize` and then `git reset --hard |
560 | fb47ddb2db...`, you might just want to tell Git that you want to skip | |
0e25790f CC |
561 | the current commit: |
562 | ||
563 | ------------------------------------------------- | |
564 | $ git bisect skip | |
565 | ------------------------------------------------- | |
566 | ||
2de9b711 | 567 | In this case, though, Git may not eventually be able to tell the first |
a0178ae2 | 568 | bad one between some first skipped commits and a later bad commit. |
0e25790f CC |
569 | |
570 | There are also ways to automate the bisecting process if you have a | |
571 | test script that can tell a good from a bad commit. See | |
1249d8ad TK |
572 | linkgit:git-bisect[1] for more information about this and other `git |
573 | bisect` features. | |
0e25790f | 574 | |
e34caace | 575 | [[naming-commits]] |
d19fbc3c BF |
576 | Naming commits |
577 | -------------- | |
578 | ||
579 | We have seen several ways of naming commits already: | |
580 | ||
d55ae921 | 581 | - 40-hexdigit object name |
d19fbc3c BF |
582 | - branch name: refers to the commit at the head of the given |
583 | branch | |
584 | - tag name: refers to the commit pointed to by the given tag | |
585 | (we've seen branches and tags are special cases of | |
586 | <<how-git-stores-references,references>>). | |
587 | - HEAD: refers to the head of the current branch | |
588 | ||
eb6ae7f4 | 589 | There are many more; see the "SPECIFYING REVISIONS" section of the |
9d83e382 | 590 | linkgit:gitrevisions[7] man page for the complete list of ways to |
d19fbc3c BF |
591 | name revisions. Some examples: |
592 | ||
593 | ------------------------------------------------- | |
d55ae921 | 594 | $ git show fb47ddb2 # the first few characters of the object name |
d19fbc3c BF |
595 | # are usually enough to specify it uniquely |
596 | $ git show HEAD^ # the parent of the HEAD commit | |
597 | $ git show HEAD^^ # the grandparent | |
598 | $ git show HEAD~4 # the great-great-grandparent | |
599 | ------------------------------------------------- | |
600 | ||
601 | Recall that merge commits may have more than one parent; by default, | |
1249d8ad | 602 | `^` and `~` follow the first parent listed in the commit, but you can |
d19fbc3c BF |
603 | also choose: |
604 | ||
605 | ------------------------------------------------- | |
606 | $ git show HEAD^1 # show the first parent of HEAD | |
607 | $ git show HEAD^2 # show the second parent of HEAD | |
608 | ------------------------------------------------- | |
609 | ||
610 | In addition to HEAD, there are several other special names for | |
611 | commits: | |
612 | ||
613 | Merges (to be discussed later), as well as operations such as | |
6127c086 | 614 | `git reset`, which change the currently checked-out commit, generally |
d19fbc3c BF |
615 | set ORIG_HEAD to the value HEAD had before the current operation. |
616 | ||
6127c086 FC |
617 | The `git fetch` operation always stores the head of the last fetched |
618 | branch in FETCH_HEAD. For example, if you run `git fetch` without | |
d19fbc3c BF |
619 | specifying a local branch as the target of the operation |
620 | ||
621 | ------------------------------------------------- | |
622 | $ git fetch git://example.com/proj.git theirbranch | |
623 | ------------------------------------------------- | |
624 | ||
625 | the fetched commits will still be available from FETCH_HEAD. | |
626 | ||
627 | When we discuss merges we'll also see the special name MERGE_HEAD, | |
628 | which refers to the other branch that we're merging in to the current | |
629 | branch. | |
630 | ||
5162e697 | 631 | The linkgit:git-rev-parse[1] command is a low-level command that is |
d55ae921 BF |
632 | occasionally useful for translating some name for a commit to the object |
633 | name for that commit: | |
aec053bb BF |
634 | |
635 | ------------------------------------------------- | |
636 | $ git rev-parse origin | |
637 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
638 | ------------------------------------------------- | |
639 | ||
e34caace | 640 | [[creating-tags]] |
d19fbc3c BF |
641 | Creating tags |
642 | ------------- | |
643 | ||
644 | We can also create a tag to refer to a particular commit; after | |
645 | running | |
646 | ||
647 | ------------------------------------------------- | |
04483524 | 648 | $ git tag stable-1 1b2e1d63ff |
d19fbc3c BF |
649 | ------------------------------------------------- |
650 | ||
1249d8ad | 651 | You can use `stable-1` to refer to the commit 1b2e1d63ff. |
d19fbc3c | 652 | |
c64415e2 BF |
653 | This creates a "lightweight" tag. If you would also like to include a |
654 | comment with the tag, and possibly sign it cryptographically, then you | |
5162e697 | 655 | should create a tag object instead; see the linkgit:git-tag[1] man page |
c64415e2 | 656 | for details. |
d19fbc3c | 657 | |
e34caace | 658 | [[browsing-revisions]] |
d19fbc3c BF |
659 | Browsing revisions |
660 | ------------------ | |
661 | ||
5162e697 | 662 | The linkgit:git-log[1] command can show lists of commits. On its |
d19fbc3c BF |
663 | own, it shows all commits reachable from the parent commit; but you |
664 | can also make more specific requests: | |
665 | ||
666 | ------------------------------------------------- | |
667 | $ git log v2.5.. # commits since (not reachable from) v2.5 | |
668 | $ git log test..master # commits reachable from master but not test | |
669 | $ git log master..test # ...reachable from test but not master | |
670 | $ git log master...test # ...reachable from either test or master, | |
671 | # but not both | |
672 | $ git log --since="2 weeks ago" # commits from the last 2 weeks | |
673 | $ git log Makefile # commits which modify Makefile | |
674 | $ git log fs/ # ... which modify any file under fs/ | |
675 | $ git log -S'foo()' # commits which add or remove any file data | |
676 | # matching the string 'foo()' | |
677 | ------------------------------------------------- | |
678 | ||
679 | And of course you can combine all of these; the following finds | |
1249d8ad | 680 | commits since v2.5 which touch the `Makefile` or any file under `fs`: |
d19fbc3c BF |
681 | |
682 | ------------------------------------------------- | |
683 | $ git log v2.5.. Makefile fs/ | |
684 | ------------------------------------------------- | |
685 | ||
686 | You can also ask git log to show patches: | |
687 | ||
688 | ------------------------------------------------- | |
689 | $ git log -p | |
690 | ------------------------------------------------- | |
691 | ||
1249d8ad | 692 | See the `--pretty` option in the linkgit:git-log[1] man page for more |
d19fbc3c BF |
693 | display options. |
694 | ||
695 | Note that git log starts with the most recent commit and works | |
2de9b711 | 696 | backwards through the parents; however, since Git history can contain |
3dff5379 | 697 | multiple independent lines of development, the particular order that |
d19fbc3c BF |
698 | commits are listed in may be somewhat arbitrary. |
699 | ||
e34caace | 700 | [[generating-diffs]] |
d19fbc3c BF |
701 | Generating diffs |
702 | ---------------- | |
703 | ||
704 | You can generate diffs between any two versions using | |
5162e697 | 705 | linkgit:git-diff[1]: |
d19fbc3c BF |
706 | |
707 | ------------------------------------------------- | |
708 | $ git diff master..test | |
709 | ------------------------------------------------- | |
710 | ||
5b98d9bc BF |
711 | That will produce the diff between the tips of the two branches. If |
712 | you'd prefer to find the diff from their common ancestor to test, you | |
713 | can use three dots instead of two: | |
714 | ||
715 | ------------------------------------------------- | |
716 | $ git diff master...test | |
717 | ------------------------------------------------- | |
718 | ||
719 | Sometimes what you want instead is a set of patches; for this you can | |
5162e697 | 720 | use linkgit:git-format-patch[1]: |
d19fbc3c BF |
721 | |
722 | ------------------------------------------------- | |
723 | $ git format-patch master..test | |
724 | ------------------------------------------------- | |
725 | ||
726 | will generate a file with a patch for each commit reachable from test | |
5b98d9bc | 727 | but not from master. |
d19fbc3c | 728 | |
e34caace | 729 | [[viewing-old-file-versions]] |
d19fbc3c BF |
730 | Viewing old file versions |
731 | ------------------------- | |
732 | ||
733 | You can always view an old version of a file by just checking out the | |
734 | correct revision first. But sometimes it is more convenient to be | |
735 | able to view an old version of a single file without checking | |
736 | anything out; this command does that: | |
737 | ||
738 | ------------------------------------------------- | |
739 | $ git show v2.5:fs/locks.c | |
740 | ------------------------------------------------- | |
741 | ||
742 | Before the colon may be anything that names a commit, and after it | |
2de9b711 | 743 | may be any path to a file tracked by Git. |
d19fbc3c | 744 | |
e34caace | 745 | [[history-examples]] |
aec053bb BF |
746 | Examples |
747 | -------- | |
748 | ||
46acd3fa BF |
749 | [[counting-commits-on-a-branch]] |
750 | Counting the number of commits on a branch | |
751 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
752 | ||
1249d8ad TK |
753 | Suppose you want to know how many commits you've made on `mybranch` |
754 | since it diverged from `origin`: | |
46acd3fa BF |
755 | |
756 | ------------------------------------------------- | |
757 | $ git log --pretty=oneline origin..mybranch | wc -l | |
758 | ------------------------------------------------- | |
759 | ||
760 | Alternatively, you may often see this sort of thing done with the | |
a6e5ef7d | 761 | lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's |
46acd3fa BF |
762 | of all the given commits: |
763 | ||
764 | ------------------------------------------------- | |
765 | $ git rev-list origin..mybranch | wc -l | |
766 | ------------------------------------------------- | |
767 | ||
e34caace | 768 | [[checking-for-equal-branches]] |
aec053bb | 769 | Check whether two branches point at the same history |
2f99710c | 770 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
aec053bb BF |
771 | |
772 | Suppose you want to check whether two branches point at the same point | |
773 | in history. | |
774 | ||
775 | ------------------------------------------------- | |
776 | $ git diff origin..master | |
777 | ------------------------------------------------- | |
778 | ||
69f7ad73 BF |
779 | will tell you whether the contents of the project are the same at the |
780 | two branches; in theory, however, it's possible that the same project | |
781 | contents could have been arrived at by two different historical | |
d55ae921 | 782 | routes. You could compare the object names: |
aec053bb BF |
783 | |
784 | ------------------------------------------------- | |
785 | $ git rev-list origin | |
786 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
787 | $ git rev-list master | |
788 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
789 | ------------------------------------------------- | |
790 | ||
1249d8ad | 791 | Or you could recall that the `...` operator selects all commits |
ddd4ddef | 792 | reachable from either one reference or the other but not |
ddd2369c | 793 | both; so |
aec053bb BF |
794 | |
795 | ------------------------------------------------- | |
796 | $ git log origin...master | |
797 | ------------------------------------------------- | |
798 | ||
799 | will return no commits when the two branches are equal. | |
800 | ||
e34caace | 801 | [[finding-tagged-descendants]] |
b181d57f BF |
802 | Find first tagged version including a given fix |
803 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
aec053bb | 804 | |
69f7ad73 BF |
805 | Suppose you know that the commit e05db0fd fixed a certain problem. |
806 | You'd like to find the earliest tagged release that contains that | |
807 | fix. | |
808 | ||
809 | Of course, there may be more than one answer--if the history branched | |
810 | after commit e05db0fd, then there could be multiple "earliest" tagged | |
811 | releases. | |
812 | ||
813 | You could just visually inspect the commits since e05db0fd: | |
814 | ||
815 | ------------------------------------------------- | |
816 | $ gitk e05db0fd.. | |
817 | ------------------------------------------------- | |
818 | ||
ddd4ddef | 819 | or you can use linkgit:git-name-rev[1], which will give the commit a |
b181d57f BF |
820 | name based on any tag it finds pointing to one of the commit's |
821 | descendants: | |
822 | ||
823 | ------------------------------------------------- | |
04483524 | 824 | $ git name-rev --tags e05db0fd |
b181d57f BF |
825 | e05db0fd tags/v1.5.0-rc1^0~23 |
826 | ------------------------------------------------- | |
827 | ||
5162e697 | 828 | The linkgit:git-describe[1] command does the opposite, naming the |
b181d57f BF |
829 | revision using a tag on which the given commit is based: |
830 | ||
831 | ------------------------------------------------- | |
832 | $ git describe e05db0fd | |
04483524 | 833 | v1.5.0-rc0-260-ge05db0f |
b181d57f BF |
834 | ------------------------------------------------- |
835 | ||
836 | but that may sometimes help you guess which tags might come after the | |
837 | given commit. | |
838 | ||
839 | If you just want to verify whether a given tagged version contains a | |
5162e697 | 840 | given commit, you could use linkgit:git-merge-base[1]: |
b181d57f BF |
841 | |
842 | ------------------------------------------------- | |
843 | $ git merge-base e05db0fd v1.5.0-rc1 | |
844 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
845 | ------------------------------------------------- | |
846 | ||
847 | The merge-base command finds a common ancestor of the given commits, | |
848 | and always returns one or the other in the case where one is a | |
849 | descendant of the other; so the above output shows that e05db0fd | |
850 | actually is an ancestor of v1.5.0-rc1. | |
851 | ||
852 | Alternatively, note that | |
853 | ||
854 | ------------------------------------------------- | |
4a7979ca | 855 | $ git log v1.5.0-rc1..e05db0fd |
b181d57f BF |
856 | ------------------------------------------------- |
857 | ||
4a7979ca | 858 | will produce empty output if and only if v1.5.0-rc1 includes e05db0fd, |
b181d57f | 859 | because it outputs only commits that are not reachable from v1.5.0-rc1. |
aec053bb | 860 | |
5162e697 | 861 | As yet another alternative, the linkgit:git-show-branch[1] command lists |
4a7979ca | 862 | the commits reachable from its arguments with a display on the left-hand |
ddd4ddef TA |
863 | side that indicates which arguments that commit is reachable from. |
864 | So, if you run something like | |
4a7979ca BF |
865 | |
866 | ------------------------------------------------- | |
867 | $ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2 | |
868 | ! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
869 | available | |
870 | ! [v1.5.0-rc0] GIT v1.5.0 preview | |
871 | ! [v1.5.0-rc1] GIT v1.5.0-rc1 | |
872 | ! [v1.5.0-rc2] GIT v1.5.0-rc2 | |
873 | ... | |
874 | ------------------------------------------------- | |
875 | ||
ddd4ddef | 876 | then a line like |
4a7979ca BF |
877 | |
878 | ------------------------------------------------- | |
879 | + ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
880 | available | |
881 | ------------------------------------------------- | |
882 | ||
ddd4ddef TA |
883 | shows that e05db0fd is reachable from itself, from v1.5.0-rc1, |
884 | and from v1.5.0-rc2, and not from v1.5.0-rc0. | |
4a7979ca | 885 | |
629d9f78 BF |
886 | [[showing-commits-unique-to-a-branch]] |
887 | Showing commits unique to a given branch | |
888 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
4a7979ca | 889 | |
629d9f78 | 890 | Suppose you would like to see all the commits reachable from the branch |
1249d8ad | 891 | head named `master` but not from any other head in your repository. |
d19fbc3c | 892 | |
629d9f78 | 893 | We can list all the heads in this repository with |
5162e697 | 894 | linkgit:git-show-ref[1]: |
d19fbc3c | 895 | |
629d9f78 BF |
896 | ------------------------------------------------- |
897 | $ git show-ref --heads | |
898 | bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial | |
899 | db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint | |
900 | a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master | |
901 | 24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2 | |
902 | 1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes | |
903 | ------------------------------------------------- | |
d19fbc3c | 904 | |
1249d8ad | 905 | We can get just the branch-head names, and remove `master`, with |
629d9f78 BF |
906 | the help of the standard utilities cut and grep: |
907 | ||
908 | ------------------------------------------------- | |
909 | $ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master' | |
910 | refs/heads/core-tutorial | |
911 | refs/heads/maint | |
912 | refs/heads/tutorial-2 | |
913 | refs/heads/tutorial-fixes | |
914 | ------------------------------------------------- | |
915 | ||
916 | And then we can ask to see all the commits reachable from master | |
917 | but not from these other heads: | |
918 | ||
919 | ------------------------------------------------- | |
920 | $ gitk master --not $( git show-ref --heads | cut -d' ' -f2 | | |
921 | grep -v '^refs/heads/master' ) | |
922 | ------------------------------------------------- | |
923 | ||
924 | Obviously, endless variations are possible; for example, to see all | |
925 | commits reachable from some head but not from any tag in the repository: | |
926 | ||
927 | ------------------------------------------------- | |
c78974f7 | 928 | $ gitk $( git show-ref --heads ) --not $( git show-ref --tags ) |
629d9f78 BF |
929 | ------------------------------------------------- |
930 | ||
9d83e382 | 931 | (See linkgit:gitrevisions[7] for explanations of commit-selecting |
629d9f78 BF |
932 | syntax such as `--not`.) |
933 | ||
82c8bf28 BF |
934 | [[making-a-release]] |
935 | Creating a changelog and tarball for a software release | |
936 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
937 | ||
5162e697 | 938 | The linkgit:git-archive[1] command can create a tar or zip archive from |
82c8bf28 BF |
939 | any version of a project; for example: |
940 | ||
941 | ------------------------------------------------- | |
7ed1690c | 942 | $ git archive -o latest.tar.gz --prefix=project/ HEAD |
82c8bf28 BF |
943 | ------------------------------------------------- |
944 | ||
7ed1690c TK |
945 | will use HEAD to produce a gzipped tar archive in which each filename |
946 | is preceded by `project/`. The output file format is inferred from | |
947 | the output file extension if possible, see linkgit:git-archive[1] for | |
948 | details. | |
949 | ||
1249d8ad | 950 | Versions of Git older than 1.7.7 don't know about the `tar.gz` format, |
7ed1690c TK |
951 | you'll need to use gzip explicitly: |
952 | ||
953 | ------------------------------------------------- | |
954 | $ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz | |
955 | ------------------------------------------------- | |
82c8bf28 BF |
956 | |
957 | If you're releasing a new version of a software project, you may want | |
958 | to simultaneously make a changelog to include in the release | |
959 | announcement. | |
960 | ||
961 | Linus Torvalds, for example, makes new kernel releases by tagging them, | |
962 | then running: | |
963 | ||
964 | ------------------------------------------------- | |
965 | $ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7 | |
966 | ------------------------------------------------- | |
967 | ||
968 | where release-script is a shell script that looks like: | |
969 | ||
970 | ------------------------------------------------- | |
971 | #!/bin/sh | |
972 | stable="$1" | |
973 | last="$2" | |
974 | new="$3" | |
975 | echo "# git tag v$new" | |
976 | echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz" | |
977 | echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz" | |
978 | echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new" | |
979 | echo "git shortlog --no-merges v$new ^v$last > ../ShortLog" | |
980 | echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new" | |
981 | ------------------------------------------------- | |
982 | ||
983 | and then he just cut-and-pastes the output commands after verifying that | |
984 | they look OK. | |
4a7979ca | 985 | |
e1ba4c32 | 986 | [[Finding-commits-With-given-Content]] |
187b0d80 | 987 | Finding commits referencing a file with given content |
d5821de2 | 988 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
187b0d80 BF |
989 | |
990 | Somebody hands you a copy of a file, and asks which commits modified a | |
991 | file such that it contained the given content either before or after the | |
992 | commit. You can find out with this: | |
993 | ||
994 | ------------------------------------------------- | |
477ff5b7 | 995 | $ git log --raw --abbrev=40 --pretty=oneline | |
187b0d80 BF |
996 | grep -B 1 `git hash-object filename` |
997 | ------------------------------------------------- | |
998 | ||
999 | Figuring out why this works is left as an exercise to the (advanced) | |
5162e697 DM |
1000 | student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and |
1001 | linkgit:git-hash-object[1] man pages may prove helpful. | |
187b0d80 | 1002 | |
aa971cb9 | 1003 | [[Developing-With-git]] |
2de9b711 | 1004 | Developing with Git |
d19fbc3c BF |
1005 | =================== |
1006 | ||
e34caace | 1007 | [[telling-git-your-name]] |
2de9b711 | 1008 | Telling Git your name |
d19fbc3c BF |
1009 | --------------------- |
1010 | ||
632cc3e6 TK |
1011 | Before creating any commits, you should introduce yourself to Git. |
1012 | The easiest way to do so is to use linkgit:git-config[1]: | |
1013 | ||
1014 | ------------------------------------------------ | |
1015 | $ git config --global user.name 'Your Name Comes Here' | |
1016 | $ git config --global user.email 'you@yourdomain.example.com' | |
1017 | ------------------------------------------------ | |
1018 | ||
1019 | Which will add the following to a file named `.gitconfig` in your | |
1020 | home directory: | |
d19fbc3c BF |
1021 | |
1022 | ------------------------------------------------ | |
d19fbc3c BF |
1023 | [user] |
1024 | name = Your Name Comes Here | |
1025 | email = you@yourdomain.example.com | |
d19fbc3c BF |
1026 | ------------------------------------------------ |
1027 | ||
632cc3e6 TK |
1028 | See the "CONFIGURATION FILE" section of linkgit:git-config[1] for |
1029 | details on the configuration file. The file is plain text, so you can | |
1030 | also edit it with your favorite editor. | |
fc90c536 | 1031 | |
d19fbc3c | 1032 | |
e34caace | 1033 | [[creating-a-new-repository]] |
d19fbc3c BF |
1034 | Creating a new repository |
1035 | ------------------------- | |
1036 | ||
1037 | Creating a new repository from scratch is very easy: | |
1038 | ||
1039 | ------------------------------------------------- | |
1040 | $ mkdir project | |
1041 | $ cd project | |
f1d2b477 | 1042 | $ git init |
d19fbc3c BF |
1043 | ------------------------------------------------- |
1044 | ||
1045 | If you have some initial content (say, a tarball): | |
1046 | ||
1047 | ------------------------------------------------- | |
0ddd93b2 | 1048 | $ tar xzvf project.tar.gz |
d19fbc3c | 1049 | $ cd project |
f1d2b477 | 1050 | $ git init |
d19fbc3c BF |
1051 | $ git add . # include everything below ./ in the first commit: |
1052 | $ git commit | |
1053 | ------------------------------------------------- | |
1054 | ||
1055 | [[how-to-make-a-commit]] | |
ae25c67a | 1056 | How to make a commit |
d19fbc3c BF |
1057 | -------------------- |
1058 | ||
1059 | Creating a new commit takes three steps: | |
1060 | ||
1061 | 1. Making some changes to the working directory using your | |
1062 | favorite editor. | |
2de9b711 TA |
1063 | 2. Telling Git about your changes. |
1064 | 3. Creating the commit using the content you told Git about | |
d19fbc3c BF |
1065 | in step 2. |
1066 | ||
1067 | In practice, you can interleave and repeat steps 1 and 2 as many | |
1068 | times as you want: in order to keep track of what you want committed | |
2de9b711 | 1069 | at step 3, Git maintains a snapshot of the tree's contents in a |
d19fbc3c BF |
1070 | special staging area called "the index." |
1071 | ||
01997b4a | 1072 | At the beginning, the content of the index will be identical to |
1249d8ad | 1073 | that of the HEAD. The command `git diff --cached`, which shows |
01997b4a BF |
1074 | the difference between the HEAD and the index, should therefore |
1075 | produce no output at that point. | |
eb6ae7f4 | 1076 | |
d19fbc3c BF |
1077 | Modifying the index is easy: |
1078 | ||
d39765b1 | 1079 | To update the index with the contents of a new or modified file, use |
d19fbc3c BF |
1080 | |
1081 | ------------------------------------------------- | |
1082 | $ git add path/to/file | |
1083 | ------------------------------------------------- | |
1084 | ||
d39765b1 | 1085 | To remove a file from the index and from the working tree, use |
d19fbc3c BF |
1086 | |
1087 | ------------------------------------------------- | |
1088 | $ git rm path/to/file | |
1089 | ------------------------------------------------- | |
1090 | ||
1091 | After each step you can verify that | |
1092 | ||
1093 | ------------------------------------------------- | |
1094 | $ git diff --cached | |
1095 | ------------------------------------------------- | |
1096 | ||
1097 | always shows the difference between the HEAD and the index file--this | |
1098 | is what you'd commit if you created the commit now--and that | |
1099 | ||
1100 | ------------------------------------------------- | |
1101 | $ git diff | |
1102 | ------------------------------------------------- | |
1103 | ||
1104 | shows the difference between the working tree and the index file. | |
1105 | ||
1249d8ad | 1106 | Note that `git add` always adds just the current contents of a file |
d19fbc3c | 1107 | to the index; further changes to the same file will be ignored unless |
6127c086 | 1108 | you run `git add` on the file again. |
d19fbc3c BF |
1109 | |
1110 | When you're ready, just run | |
1111 | ||
1112 | ------------------------------------------------- | |
1113 | $ git commit | |
1114 | ------------------------------------------------- | |
1115 | ||
2de9b711 | 1116 | and Git will prompt you for a commit message and then create the new |
3dff5379 | 1117 | commit. Check to make sure it looks like what you expected with |
d19fbc3c BF |
1118 | |
1119 | ------------------------------------------------- | |
1120 | $ git show | |
1121 | ------------------------------------------------- | |
1122 | ||
1123 | As a special shortcut, | |
a6080a0a | 1124 | |
d19fbc3c BF |
1125 | ------------------------------------------------- |
1126 | $ git commit -a | |
1127 | ------------------------------------------------- | |
1128 | ||
1129 | will update the index with any files that you've modified or removed | |
1130 | and create a commit, all in one step. | |
1131 | ||
1132 | A number of commands are useful for keeping track of what you're | |
1133 | about to commit: | |
1134 | ||
1135 | ------------------------------------------------- | |
1136 | $ git diff --cached # difference between HEAD and the index; what | |
1130845b | 1137 | # would be committed if you ran "commit" now. |
d19fbc3c BF |
1138 | $ git diff # difference between the index file and your |
1139 | # working directory; changes that would not | |
1140 | # be included if you ran "commit" now. | |
c64415e2 BF |
1141 | $ git diff HEAD # difference between HEAD and working tree; what |
1142 | # would be committed if you ran "commit -a" now. | |
d19fbc3c BF |
1143 | $ git status # a brief per-file summary of the above. |
1144 | ------------------------------------------------- | |
1145 | ||
5162e697 | 1146 | You can also use linkgit:git-gui[1] to create commits, view changes in |
407c0c87 BF |
1147 | the index and the working tree files, and individually select diff hunks |
1148 | for inclusion in the index (by right-clicking on the diff hunk and | |
1149 | choosing "Stage Hunk For Commit"). | |
1150 | ||
e34caace | 1151 | [[creating-good-commit-messages]] |
ae25c67a | 1152 | Creating good commit messages |
d19fbc3c BF |
1153 | ----------------------------- |
1154 | ||
1155 | Though not required, it's a good idea to begin the commit message | |
1156 | with a single short (less than 50 character) line summarizing the | |
1157 | change, followed by a blank line and then a more thorough | |
52ffe995 JW |
1158 | description. The text up to the first blank line in a commit |
1159 | message is treated as the commit title, and that title is used | |
2de9b711 | 1160 | throughout Git. For example, linkgit:git-format-patch[1] turns a |
52ffe995 JW |
1161 | commit into email, and it uses the title on the Subject line and the |
1162 | rest of the commit in the body. | |
1163 | ||
d19fbc3c | 1164 | |
2dc53617 JH |
1165 | [[ignoring-files]] |
1166 | Ignoring files | |
1167 | -------------- | |
1168 | ||
2de9b711 | 1169 | A project will often generate files that you do 'not' want to track with Git. |
2dc53617 | 1170 | This typically includes files generated by a build process or temporary |
2de9b711 | 1171 | backup files made by your editor. Of course, 'not' tracking files with Git |
6127c086 | 1172 | is just a matter of 'not' calling `git add` on them. But it quickly becomes |
2dc53617 | 1173 | annoying to have these untracked files lying around; e.g. they make |
dcb11263 CJ |
1174 | `git add .` practically useless, and they keep showing up in the output of |
1175 | `git status`. | |
2dc53617 | 1176 | |
1249d8ad TK |
1177 | You can tell Git to ignore certain files by creating a file called |
1178 | `.gitignore` in the top level of your working directory, with contents | |
1179 | such as: | |
2dc53617 JH |
1180 | |
1181 | ------------------------------------------------- | |
1182 | # Lines starting with '#' are considered comments. | |
464a8a7a | 1183 | # Ignore any file named foo.txt. |
2dc53617 JH |
1184 | foo.txt |
1185 | # Ignore (generated) html files, | |
1186 | *.html | |
1187 | # except foo.html which is maintained by hand. | |
1188 | !foo.html | |
1189 | # Ignore objects and archives. | |
1190 | *.[oa] | |
1191 | ------------------------------------------------- | |
1192 | ||
5162e697 | 1193 | See linkgit:gitignore[5] for a detailed explanation of the syntax. You can |
464a8a7a BF |
1194 | also place .gitignore files in other directories in your working tree, and they |
1195 | will apply to those directories and their subdirectories. The `.gitignore` | |
1196 | files can be added to your repository like any other files (just run `git add | |
1197 | .gitignore` and `git commit`, as usual), which is convenient when the exclude | |
1198 | patterns (such as patterns matching build output files) would also make sense | |
1199 | for other users who clone your repository. | |
1200 | ||
1201 | If you wish the exclude patterns to affect only certain repositories | |
1202 | (instead of every repository for a given project), you may instead put | |
1249d8ad TK |
1203 | them in a file in your repository named `.git/info/exclude`, or in any |
1204 | file specified by the `core.excludesfile` configuration variable. | |
1205 | Some Git commands can also take exclude patterns directly on the | |
1206 | command line. See linkgit:gitignore[5] for the details. | |
2dc53617 | 1207 | |
e34caace | 1208 | [[how-to-merge]] |
ae25c67a | 1209 | How to merge |
d19fbc3c BF |
1210 | ------------ |
1211 | ||
1212 | You can rejoin two diverging branches of development using | |
5162e697 | 1213 | linkgit:git-merge[1]: |
d19fbc3c BF |
1214 | |
1215 | ------------------------------------------------- | |
1216 | $ git merge branchname | |
1217 | ------------------------------------------------- | |
1218 | ||
1249d8ad | 1219 | merges the development in the branch `branchname` into the current |
e63ec003 MM |
1220 | branch. |
1221 | ||
1249d8ad | 1222 | A merge is made by combining the changes made in `branchname` and the |
e63ec003 MM |
1223 | changes made up to the latest commit in your current branch since |
1224 | their histories forked. The work tree is overwritten by the result of | |
1225 | the merge when this combining is done cleanly, or overwritten by a | |
1226 | half-merged results when this combining results in conflicts. | |
1227 | Therefore, if you have uncommitted changes touching the same files as | |
1228 | the ones impacted by the merge, Git will refuse to proceed. Most of | |
1229 | the time, you will want to commit your changes before you can merge, | |
1230 | and if you don't, then linkgit:git-stash[1] can take these changes | |
1231 | away while you're doing the merge, and reapply them afterwards. | |
1232 | ||
6a5d0b0a | 1233 | If the changes are independent enough, Git will automatically complete |
e63ec003 MM |
1234 | the merge and commit the result (or reuse an existing commit in case |
1235 | of <<fast-forwards,fast-forward>>, see below). On the other hand, | |
1236 | if there are conflicts--for example, if the same file is | |
d19fbc3c BF |
1237 | modified in two different ways in the remote branch and the local |
1238 | branch--then you are warned; the output may look something like this: | |
1239 | ||
1240 | ------------------------------------------------- | |
fabbd8f6 BF |
1241 | $ git merge next |
1242 | 100% (4/4) done | |
1243 | Auto-merged file.txt | |
d19fbc3c BF |
1244 | CONFLICT (content): Merge conflict in file.txt |
1245 | Automatic merge failed; fix conflicts and then commit the result. | |
1246 | ------------------------------------------------- | |
1247 | ||
1248 | Conflict markers are left in the problematic files, and after | |
1249 | you resolve the conflicts manually, you can update the index | |
2de9b711 | 1250 | with the contents and run Git commit, as you normally would when |
d19fbc3c BF |
1251 | creating a new file. |
1252 | ||
1253 | If you examine the resulting commit using gitk, you will see that it | |
1254 | has two parents, one pointing to the top of the current branch, and | |
1255 | one to the top of the other branch. | |
1256 | ||
d19fbc3c BF |
1257 | [[resolving-a-merge]] |
1258 | Resolving a merge | |
1259 | ----------------- | |
1260 | ||
2de9b711 | 1261 | When a merge isn't resolved automatically, Git leaves the index and |
d19fbc3c BF |
1262 | the working tree in a special state that gives you all the |
1263 | information you need to help resolve the merge. | |
1264 | ||
1265 | Files with conflicts are marked specially in the index, so until you | |
5162e697 | 1266 | resolve the problem and update the index, linkgit:git-commit[1] will |
ef561ac7 | 1267 | fail: |
d19fbc3c BF |
1268 | |
1269 | ------------------------------------------------- | |
1270 | $ git commit | |
1271 | file.txt: needs merge | |
1272 | ------------------------------------------------- | |
1273 | ||
5162e697 | 1274 | Also, linkgit:git-status[1] will list those files as "unmerged", and the |
ef561ac7 BF |
1275 | files with conflicts will have conflict markers added, like this: |
1276 | ||
1277 | ------------------------------------------------- | |
1278 | <<<<<<< HEAD:file.txt | |
1279 | Hello world | |
1280 | ======= | |
1281 | Goodbye | |
1282 | >>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1283 | ------------------------------------------------- | |
1284 | ||
1285 | All you need to do is edit the files to resolve the conflicts, and then | |
1286 | ||
1287 | ------------------------------------------------- | |
1288 | $ git add file.txt | |
1289 | $ git commit | |
1290 | ------------------------------------------------- | |
1291 | ||
1292 | Note that the commit message will already be filled in for you with | |
1293 | some information about the merge. Normally you can just use this | |
1294 | default message unchanged, but you may add additional commentary of | |
1295 | your own if desired. | |
1296 | ||
2de9b711 | 1297 | The above is all you need to know to resolve a simple merge. But Git |
ef561ac7 BF |
1298 | also provides more information to help resolve conflicts: |
1299 | ||
e34caace | 1300 | [[conflict-resolution]] |
ef561ac7 BF |
1301 | Getting conflict-resolution help during a merge |
1302 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 1303 | |
2de9b711 | 1304 | All of the changes that Git was able to merge automatically are |
5162e697 | 1305 | already added to the index file, so linkgit:git-diff[1] shows only |
ef561ac7 | 1306 | the conflicts. It uses an unusual syntax: |
d19fbc3c BF |
1307 | |
1308 | ------------------------------------------------- | |
1309 | $ git diff | |
1310 | diff --cc file.txt | |
1311 | index 802992c,2b60207..0000000 | |
1312 | --- a/file.txt | |
1313 | +++ b/file.txt | |
1314 | @@@ -1,1 -1,1 +1,5 @@@ | |
1315 | ++<<<<<<< HEAD:file.txt | |
1316 | +Hello world | |
1317 | ++======= | |
1318 | + Goodbye | |
1319 | ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1320 | ------------------------------------------------- | |
1321 | ||
1130845b | 1322 | Recall that the commit which will be committed after we resolve this |
d19fbc3c BF |
1323 | conflict will have two parents instead of the usual one: one parent |
1324 | will be HEAD, the tip of the current branch; the other will be the | |
1325 | tip of the other branch, which is stored temporarily in MERGE_HEAD. | |
1326 | ||
ef561ac7 BF |
1327 | During the merge, the index holds three versions of each file. Each of |
1328 | these three "file stages" represents a different version of the file: | |
1329 | ||
1330 | ------------------------------------------------- | |
1331 | $ git show :1:file.txt # the file in a common ancestor of both branches | |
4209752d JH |
1332 | $ git show :2:file.txt # the version from HEAD. |
1333 | $ git show :3:file.txt # the version from MERGE_HEAD. | |
ef561ac7 BF |
1334 | ------------------------------------------------- |
1335 | ||
4209752d JH |
1336 | When you ask linkgit:git-diff[1] to show the conflicts, it runs a |
1337 | three-way diff between the conflicted merge results in the work tree with | |
1338 | stages 2 and 3 to show only hunks whose contents come from both sides, | |
1339 | mixed (in other words, when a hunk's merge results come only from stage 2, | |
1340 | that part is not conflicting and is not shown. Same for stage 3). | |
ef561ac7 BF |
1341 | |
1342 | The diff above shows the differences between the working-tree version of | |
1343 | file.txt and the stage 2 and stage 3 versions. So instead of preceding | |
1249d8ad | 1344 | each line by a single `+` or `-`, it now uses two columns: the first |
ef561ac7 BF |
1345 | column is used for differences between the first parent and the working |
1346 | directory copy, and the second for differences between the second parent | |
1347 | and the working directory copy. (See the "COMBINED DIFF FORMAT" section | |
5162e697 | 1348 | of linkgit:git-diff-files[1] for a details of the format.) |
ef561ac7 BF |
1349 | |
1350 | After resolving the conflict in the obvious way (but before updating the | |
1351 | index), the diff will look like: | |
d19fbc3c BF |
1352 | |
1353 | ------------------------------------------------- | |
1354 | $ git diff | |
1355 | diff --cc file.txt | |
1356 | index 802992c,2b60207..0000000 | |
1357 | --- a/file.txt | |
1358 | +++ b/file.txt | |
1359 | @@@ -1,1 -1,1 +1,1 @@@ | |
1360 | - Hello world | |
1361 | -Goodbye | |
1362 | ++Goodbye world | |
1363 | ------------------------------------------------- | |
1364 | ||
1365 | This shows that our resolved version deleted "Hello world" from the | |
1366 | first parent, deleted "Goodbye" from the second parent, and added | |
1367 | "Goodbye world", which was previously absent from both. | |
1368 | ||
ef561ac7 BF |
1369 | Some special diff options allow diffing the working directory against |
1370 | any of these stages: | |
1371 | ||
1372 | ------------------------------------------------- | |
1373 | $ git diff -1 file.txt # diff against stage 1 | |
1374 | $ git diff --base file.txt # same as the above | |
1375 | $ git diff -2 file.txt # diff against stage 2 | |
1376 | $ git diff --ours file.txt # same as the above | |
1377 | $ git diff -3 file.txt # diff against stage 3 | |
1378 | $ git diff --theirs file.txt # same as the above. | |
1379 | ------------------------------------------------- | |
1380 | ||
0cafe944 | 1381 | The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help |
ef561ac7 | 1382 | for merges: |
d19fbc3c BF |
1383 | |
1384 | ------------------------------------------------- | |
1385 | $ git log --merge | |
ef561ac7 | 1386 | $ gitk --merge |
d19fbc3c BF |
1387 | ------------------------------------------------- |
1388 | ||
ef561ac7 BF |
1389 | These will display all commits which exist only on HEAD or on |
1390 | MERGE_HEAD, and which touch an unmerged file. | |
d19fbc3c | 1391 | |
5162e697 | 1392 | You may also use linkgit:git-mergetool[1], which lets you merge the |
c7719fbe | 1393 | unmerged files using external tools such as Emacs or kdiff3. |
c64415e2 | 1394 | |
ef561ac7 | 1395 | Each time you resolve the conflicts in a file and update the index: |
d19fbc3c BF |
1396 | |
1397 | ------------------------------------------------- | |
1398 | $ git add file.txt | |
d19fbc3c BF |
1399 | ------------------------------------------------- |
1400 | ||
ef561ac7 | 1401 | the different stages of that file will be "collapsed", after which |
6127c086 | 1402 | `git diff` will (by default) no longer show diffs for that file. |
d19fbc3c BF |
1403 | |
1404 | [[undoing-a-merge]] | |
ae25c67a | 1405 | Undoing a merge |
d19fbc3c BF |
1406 | --------------- |
1407 | ||
1408 | If you get stuck and decide to just give up and throw the whole mess | |
1409 | away, you can always return to the pre-merge state with | |
1410 | ||
1411 | ------------------------------------------------- | |
1412 | $ git reset --hard HEAD | |
1413 | ------------------------------------------------- | |
1414 | ||
1130845b | 1415 | Or, if you've already committed the merge that you want to throw away, |
d19fbc3c BF |
1416 | |
1417 | ------------------------------------------------- | |
1c73bb0e | 1418 | $ git reset --hard ORIG_HEAD |
d19fbc3c BF |
1419 | ------------------------------------------------- |
1420 | ||
1421 | However, this last command can be dangerous in some cases--never | |
1422 | throw away a commit you have already committed if that commit may | |
1423 | itself have been merged into another branch, as doing so may confuse | |
1424 | further merges. | |
1425 | ||
e34caace | 1426 | [[fast-forwards]] |
d19fbc3c BF |
1427 | Fast-forward merges |
1428 | ------------------- | |
1429 | ||
1430 | There is one special case not mentioned above, which is treated | |
1431 | differently. Normally, a merge results in a merge commit, with two | |
1432 | parents, one pointing at each of the two lines of development that | |
1433 | were merged. | |
1434 | ||
59723040 | 1435 | However, if the current branch is a descendant of the other--so every |
2de9b711 | 1436 | commit present in the one is already contained in the other--then Git |
a75d7b54 | 1437 | just performs a "fast-forward"; the head of the current branch is moved |
59723040 BF |
1438 | forward to point at the head of the merged-in branch, without any new |
1439 | commits being created. | |
d19fbc3c | 1440 | |
e34caace | 1441 | [[fixing-mistakes]] |
b684f830 BF |
1442 | Fixing mistakes |
1443 | --------------- | |
1444 | ||
1445 | If you've messed up the working tree, but haven't yet committed your | |
1446 | mistake, you can return the entire working tree to the last committed | |
1447 | state with | |
1448 | ||
1449 | ------------------------------------------------- | |
1450 | $ git reset --hard HEAD | |
1451 | ------------------------------------------------- | |
1452 | ||
1453 | If you make a commit that you later wish you hadn't, there are two | |
1454 | fundamentally different ways to fix the problem: | |
1455 | ||
1456 | 1. You can create a new commit that undoes whatever was done | |
93cbbd71 | 1457 | by the old commit. This is the correct thing if your |
b684f830 BF |
1458 | mistake has already been made public. |
1459 | ||
1460 | 2. You can go back and modify the old commit. You should | |
1461 | never do this if you have already made the history public; | |
2de9b711 | 1462 | Git does not normally expect the "history" of a project to |
b684f830 BF |
1463 | change, and cannot correctly perform repeated merges from |
1464 | a branch that has had its history changed. | |
1465 | ||
e34caace | 1466 | [[reverting-a-commit]] |
b684f830 BF |
1467 | Fixing a mistake with a new commit |
1468 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1469 | ||
1470 | Creating a new commit that reverts an earlier change is very easy; | |
5162e697 | 1471 | just pass the linkgit:git-revert[1] command a reference to the bad |
b684f830 BF |
1472 | commit; for example, to revert the most recent commit: |
1473 | ||
1474 | ------------------------------------------------- | |
1475 | $ git revert HEAD | |
1476 | ------------------------------------------------- | |
1477 | ||
1478 | This will create a new commit which undoes the change in HEAD. You | |
1479 | will be given a chance to edit the commit message for the new commit. | |
1480 | ||
1481 | You can also revert an earlier change, for example, the next-to-last: | |
1482 | ||
1483 | ------------------------------------------------- | |
1484 | $ git revert HEAD^ | |
1485 | ------------------------------------------------- | |
1486 | ||
2de9b711 | 1487 | In this case Git will attempt to undo the old change while leaving |
b684f830 BF |
1488 | intact any changes made since then. If more recent changes overlap |
1489 | with the changes to be reverted, then you will be asked to fix | |
1490 | conflicts manually, just as in the case of <<resolving-a-merge, | |
1491 | resolving a merge>>. | |
1492 | ||
7cb192ea BF |
1493 | [[fixing-a-mistake-by-rewriting-history]] |
1494 | Fixing a mistake by rewriting history | |
b684f830 BF |
1495 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
1496 | ||
1497 | If the problematic commit is the most recent commit, and you have not | |
1498 | yet made that commit public, then you may just | |
6127c086 | 1499 | <<undoing-a-merge,destroy it using `git reset`>>. |
b684f830 BF |
1500 | |
1501 | Alternatively, you | |
1502 | can edit the working directory and update the index to fix your | |
1503 | mistake, just as if you were going to <<how-to-make-a-commit,create a | |
1504 | new commit>>, then run | |
1505 | ||
1506 | ------------------------------------------------- | |
1507 | $ git commit --amend | |
1508 | ------------------------------------------------- | |
1509 | ||
1510 | which will replace the old commit by a new commit incorporating your | |
1511 | changes, giving you a chance to edit the old commit message first. | |
1512 | ||
1513 | Again, you should never do this to a commit that may already have | |
5162e697 | 1514 | been merged into another branch; use linkgit:git-revert[1] instead in |
b684f830 BF |
1515 | that case. |
1516 | ||
7cb192ea | 1517 | It is also possible to replace commits further back in the history, but |
b684f830 BF |
1518 | this is an advanced topic to be left for |
1519 | <<cleaning-up-history,another chapter>>. | |
1520 | ||
e34caace | 1521 | [[checkout-of-path]] |
b684f830 BF |
1522 | Checking out an old version of a file |
1523 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1524 | ||
1525 | In the process of undoing a previous bad change, you may find it | |
1526 | useful to check out an older version of a particular file using | |
6127c086 | 1527 | linkgit:git-checkout[1]. We've used `git checkout` before to switch |
b684f830 BF |
1528 | branches, but it has quite different behavior if it is given a path |
1529 | name: the command | |
1530 | ||
1531 | ------------------------------------------------- | |
1532 | $ git checkout HEAD^ path/to/file | |
1533 | ------------------------------------------------- | |
1534 | ||
1535 | replaces path/to/file by the contents it had in the commit HEAD^, and | |
1536 | also updates the index to match. It does not change branches. | |
1537 | ||
1538 | If you just want to look at an old version of the file, without | |
1539 | modifying the working directory, you can do that with | |
5162e697 | 1540 | linkgit:git-show[1]: |
b684f830 BF |
1541 | |
1542 | ------------------------------------------------- | |
ed4eb0d8 | 1543 | $ git show HEAD^:path/to/file |
b684f830 BF |
1544 | ------------------------------------------------- |
1545 | ||
1546 | which will display the given version of the file. | |
1547 | ||
7a7cc594 JH |
1548 | [[interrupted-work]] |
1549 | Temporarily setting aside work in progress | |
1550 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1551 | ||
1552 | While you are in the middle of working on something complicated, you | |
1553 | find an unrelated but obvious and trivial bug. You would like to fix it | |
5162e697 | 1554 | before continuing. You can use linkgit:git-stash[1] to save the current |
7a7cc594 JH |
1555 | state of your work, and after fixing the bug (or, optionally after doing |
1556 | so on a different branch and then coming back), unstash the | |
1557 | work-in-progress changes. | |
1558 | ||
1559 | ------------------------------------------------ | |
7a85f6ae | 1560 | $ git stash save "work in progress for foo feature" |
7a7cc594 JH |
1561 | ------------------------------------------------ |
1562 | ||
1563 | This command will save your changes away to the `stash`, and | |
1564 | reset your working tree and the index to match the tip of your | |
1565 | current branch. Then you can make your fix as usual. | |
1566 | ||
1567 | ------------------------------------------------ | |
1568 | ... edit and test ... | |
1569 | $ git commit -a -m "blorpl: typofix" | |
1570 | ------------------------------------------------ | |
1571 | ||
1572 | After that, you can go back to what you were working on with | |
7b8988e1 | 1573 | `git stash pop`: |
7a7cc594 JH |
1574 | |
1575 | ------------------------------------------------ | |
7b8988e1 | 1576 | $ git stash pop |
7a7cc594 JH |
1577 | ------------------------------------------------ |
1578 | ||
1579 | ||
e34caace | 1580 | [[ensuring-good-performance]] |
d19fbc3c BF |
1581 | Ensuring good performance |
1582 | ------------------------- | |
1583 | ||
2de9b711 | 1584 | On large repositories, Git depends on compression to keep the history |
901fd180 | 1585 | information from taking up too much space on disk or in memory. Some |
e1ebf212 | 1586 | Git commands may automatically run linkgit:git-gc[1], so you don't |
901fd180 TK |
1587 | have to worry about running it manually. However, compressing a large |
1588 | repository may take a while, so you may want to call `gc` explicitly | |
1589 | to avoid automatic compression kicking in when it is not convenient. | |
d19fbc3c | 1590 | |
e34caace BF |
1591 | |
1592 | [[ensuring-reliability]] | |
11e016a3 BF |
1593 | Ensuring reliability |
1594 | -------------------- | |
1595 | ||
e34caace | 1596 | [[checking-for-corruption]] |
11e016a3 BF |
1597 | Checking the repository for corruption |
1598 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1599 | ||
5162e697 | 1600 | The linkgit:git-fsck[1] command runs a number of self-consistency checks |
1191ee18 | 1601 | on the repository, and reports on any problems. This may take some |
c6a13b2c | 1602 | time. |
21dcb3b7 BF |
1603 | |
1604 | ------------------------------------------------- | |
04e50e94 | 1605 | $ git fsck |
21dcb3b7 BF |
1606 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 |
1607 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1608 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1609 | dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb | |
1610 | dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f | |
1611 | dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e | |
1612 | dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085 | |
1613 | dangling tree b24c2473f1fd3d91352a624795be026d64c8841f | |
1614 | ... | |
1615 | ------------------------------------------------- | |
1616 | ||
c6a13b2c JH |
1617 | You will see informational messages on dangling objects. They are objects |
1618 | that still exist in the repository but are no longer referenced by any of | |
1249d8ad | 1619 | your branches, and can (and will) be removed after a while with `gc`. |
b4ab1980 | 1620 | You can run `git fsck --no-dangling` to suppress these messages, and still |
c6a13b2c | 1621 | view real errors. |
1cdade2c | 1622 | |
e34caace | 1623 | [[recovering-lost-changes]] |
11e016a3 BF |
1624 | Recovering lost changes |
1625 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1626 | ||
e34caace | 1627 | [[reflogs]] |
559e4d7a BF |
1628 | Reflogs |
1629 | ^^^^^^^ | |
1630 | ||
1249d8ad TK |
1631 | Say you modify a branch with <<fixing-mistakes,`git reset --hard`>>, |
1632 | and then realize that the branch was the only reference you had to | |
1633 | that point in history. | |
559e4d7a | 1634 | |
2de9b711 | 1635 | Fortunately, Git also keeps a log, called a "reflog", of all the |
559e4d7a | 1636 | previous values of each branch. So in this case you can still find the |
a6080a0a | 1637 | old history using, for example, |
559e4d7a BF |
1638 | |
1639 | ------------------------------------------------- | |
1640 | $ git log master@{1} | |
1641 | ------------------------------------------------- | |
1642 | ||
e502c2c3 | 1643 | This lists the commits reachable from the previous version of the |
1249d8ad TK |
1644 | `master` branch head. This syntax can be used with any Git command |
1645 | that accepts a commit, not just with `git log`. Some other examples: | |
559e4d7a BF |
1646 | |
1647 | ------------------------------------------------- | |
1648 | $ git show master@{2} # See where the branch pointed 2, | |
1649 | $ git show master@{3} # 3, ... changes ago. | |
1650 | $ gitk master@{yesterday} # See where it pointed yesterday, | |
1651 | $ gitk master@{"1 week ago"} # ... or last week | |
953f3d6f BF |
1652 | $ git log --walk-reflogs master # show reflog entries for master |
1653 | ------------------------------------------------- | |
1654 | ||
1655 | A separate reflog is kept for the HEAD, so | |
1656 | ||
1657 | ------------------------------------------------- | |
1658 | $ git show HEAD@{"1 week ago"} | |
559e4d7a BF |
1659 | ------------------------------------------------- |
1660 | ||
953f3d6f BF |
1661 | will show what HEAD pointed to one week ago, not what the current branch |
1662 | pointed to one week ago. This allows you to see the history of what | |
1663 | you've checked out. | |
1664 | ||
559e4d7a | 1665 | The reflogs are kept by default for 30 days, after which they may be |
5162e697 | 1666 | pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn |
559e4d7a | 1667 | how to control this pruning, and see the "SPECIFYING REVISIONS" |
9d83e382 | 1668 | section of linkgit:gitrevisions[7] for details. |
559e4d7a | 1669 | |
2de9b711 | 1670 | Note that the reflog history is very different from normal Git history. |
559e4d7a BF |
1671 | While normal history is shared by every repository that works on the |
1672 | same project, the reflog history is not shared: it tells you only about | |
1673 | how the branches in your local repository have changed over time. | |
1674 | ||
59723040 | 1675 | [[dangling-object-recovery]] |
559e4d7a BF |
1676 | Examining dangling objects |
1677 | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
1678 | ||
59723040 BF |
1679 | In some situations the reflog may not be able to save you. For example, |
1680 | suppose you delete a branch, then realize you need the history it | |
1681 | contained. The reflog is also deleted; however, if you have not yet | |
1682 | pruned the repository, then you may still be able to find the lost | |
6127c086 | 1683 | commits in the dangling objects that `git fsck` reports. See |
59723040 | 1684 | <<dangling-objects>> for the details. |
559e4d7a BF |
1685 | |
1686 | ------------------------------------------------- | |
1687 | $ git fsck | |
1688 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 | |
1689 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1690 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1691 | ... | |
1692 | ------------------------------------------------- | |
1693 | ||
aacd404e | 1694 | You can examine |
559e4d7a BF |
1695 | one of those dangling commits with, for example, |
1696 | ||
1697 | ------------------------------------------------ | |
1698 | $ gitk 7281251ddd --not --all | |
1699 | ------------------------------------------------ | |
1700 | ||
1701 | which does what it sounds like: it says that you want to see the commit | |
1702 | history that is described by the dangling commit(s), but not the | |
1703 | history that is described by all your existing branches and tags. Thus | |
1704 | you get exactly the history reachable from that commit that is lost. | |
1705 | (And notice that it might not be just one commit: we only report the | |
1706 | "tip of the line" as being dangling, but there might be a whole deep | |
79c96c57 | 1707 | and complex commit history that was dropped.) |
559e4d7a BF |
1708 | |
1709 | If you decide you want the history back, you can always create a new | |
1710 | reference pointing to it, for example, a new branch: | |
1711 | ||
1712 | ------------------------------------------------ | |
a6080a0a | 1713 | $ git branch recovered-branch 7281251ddd |
559e4d7a BF |
1714 | ------------------------------------------------ |
1715 | ||
59723040 BF |
1716 | Other types of dangling objects (blobs and trees) are also possible, and |
1717 | dangling objects can arise in other situations. | |
1718 | ||
11e016a3 | 1719 | |
e34caace | 1720 | [[sharing-development]] |
d19fbc3c | 1721 | Sharing development with others |
b684f830 | 1722 | =============================== |
d19fbc3c | 1723 | |
aa971cb9 | 1724 | [[getting-updates-With-git-pull]] |
6127c086 | 1725 | Getting updates with git pull |
b684f830 | 1726 | ----------------------------- |
d19fbc3c | 1727 | |
e63ec003 | 1728 | After you clone a repository and commit a few changes of your own, you |
d19fbc3c BF |
1729 | may wish to check the original repository for updates and merge them |
1730 | into your own work. | |
1731 | ||
aa971cb9 | 1732 | We have already seen <<Updating-a-repository-With-git-fetch,how to |
0e615b25 | 1733 | keep remote-tracking branches up to date>> with linkgit:git-fetch[1], |
d19fbc3c BF |
1734 | and how to merge two branches. So you can merge in changes from the |
1735 | original repository's master branch with: | |
1736 | ||
1737 | ------------------------------------------------- | |
1738 | $ git fetch | |
1739 | $ git merge origin/master | |
1740 | ------------------------------------------------- | |
1741 | ||
5162e697 | 1742 | However, the linkgit:git-pull[1] command provides a way to do this in |
d19fbc3c BF |
1743 | one step: |
1744 | ||
1745 | ------------------------------------------------- | |
1746 | $ git pull origin master | |
1747 | ------------------------------------------------- | |
1748 | ||
1249d8ad TK |
1749 | In fact, if you have `master` checked out, then this branch has been |
1750 | configured by `git clone` to get changes from the HEAD branch of the | |
66a062a1 | 1751 | origin repository. So often you can |
0eb4f7cd | 1752 | accomplish the above with just a simple |
d19fbc3c BF |
1753 | |
1754 | ------------------------------------------------- | |
1755 | $ git pull | |
1756 | ------------------------------------------------- | |
1757 | ||
66a062a1 MM |
1758 | This command will fetch changes from the remote branches to your |
1759 | remote-tracking branches `origin/*`, and merge the default branch into | |
1760 | the current branch. | |
1761 | ||
29b9a66f MM |
1762 | More generally, a branch that is created from a remote-tracking branch |
1763 | will pull | |
0eb4f7cd | 1764 | by default from that branch. See the descriptions of the |
1249d8ad | 1765 | `branch.<name>.remote` and `branch.<name>.merge` options in |
5162e697 DM |
1766 | linkgit:git-config[1], and the discussion of the `--track` option in |
1767 | linkgit:git-checkout[1], to learn how to control these defaults. | |
d19fbc3c | 1768 | |
1249d8ad | 1769 | In addition to saving you keystrokes, `git pull` also helps you by |
d19fbc3c BF |
1770 | producing a default commit message documenting the branch and |
1771 | repository that you pulled from. | |
1772 | ||
1773 | (But note that no such commit will be created in the case of a | |
a75d7b54 | 1774 | <<fast-forwards,fast-forward>>; instead, your branch will just be |
79c96c57 | 1775 | updated to point to the latest commit from the upstream branch.) |
d19fbc3c | 1776 | |
1249d8ad | 1777 | The `git pull` command can also be given `.` as the "remote" repository, |
1191ee18 | 1778 | in which case it just merges in a branch from the current repository; so |
4c63ff45 BF |
1779 | the commands |
1780 | ||
1781 | ------------------------------------------------- | |
1782 | $ git pull . branch | |
1783 | $ git merge branch | |
1784 | ------------------------------------------------- | |
1785 | ||
a7bdee11 | 1786 | are roughly equivalent. |
4c63ff45 | 1787 | |
e34caace | 1788 | [[submitting-patches]] |
d19fbc3c | 1789 | Submitting patches to a project |
b684f830 | 1790 | ------------------------------- |
d19fbc3c BF |
1791 | |
1792 | If you just have a few changes, the simplest way to submit them may | |
1793 | just be to send them as patches in email: | |
1794 | ||
5162e697 | 1795 | First, use linkgit:git-format-patch[1]; for example: |
d19fbc3c BF |
1796 | |
1797 | ------------------------------------------------- | |
eb6ae7f4 | 1798 | $ git format-patch origin |
d19fbc3c BF |
1799 | ------------------------------------------------- |
1800 | ||
1801 | will produce a numbered series of files in the current directory, one | |
1249d8ad | 1802 | for each patch in the current branch but not in `origin/HEAD`. |
d19fbc3c | 1803 | |
d84cef18 PO |
1804 | `git format-patch` can include an initial "cover letter". You can insert |
1805 | commentary on individual patches after the three dash line which | |
1806 | `format-patch` places after the commit message but before the patch | |
1807 | itself. If you use `git notes` to track your cover letter material, | |
1808 | `git format-patch --notes` will include the commit's notes in a similar | |
1809 | manner. | |
1810 | ||
d19fbc3c BF |
1811 | You can then import these into your mail client and send them by |
1812 | hand. However, if you have a lot to send at once, you may prefer to | |
5162e697 | 1813 | use the linkgit:git-send-email[1] script to automate the process. |
d19fbc3c BF |
1814 | Consult the mailing list for your project first to determine how they |
1815 | prefer such patches be handled. | |
1816 | ||
e34caace | 1817 | [[importing-patches]] |
d19fbc3c | 1818 | Importing patches to a project |
b684f830 | 1819 | ------------------------------ |
d19fbc3c | 1820 | |
5162e697 | 1821 | Git also provides a tool called linkgit:git-am[1] (am stands for |
d19fbc3c BF |
1822 | "apply mailbox"), for importing such an emailed series of patches. |
1823 | Just save all of the patch-containing messages, in order, into a | |
1249d8ad | 1824 | single mailbox file, say `patches.mbox`, then run |
d19fbc3c BF |
1825 | |
1826 | ------------------------------------------------- | |
eb6ae7f4 | 1827 | $ git am -3 patches.mbox |
d19fbc3c BF |
1828 | ------------------------------------------------- |
1829 | ||
1830 | Git will apply each patch in order; if any conflicts are found, it | |
1831 | will stop, and you can fix the conflicts as described in | |
1249d8ad | 1832 | "<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells |
2de9b711 | 1833 | Git to perform a merge; if you would prefer it just to abort and |
01997b4a BF |
1834 | leave your tree and index untouched, you may omit that option.) |
1835 | ||
1836 | Once the index is updated with the results of the conflict | |
1837 | resolution, instead of creating a new commit, just run | |
d19fbc3c BF |
1838 | |
1839 | ------------------------------------------------- | |
8ceb6fbd | 1840 | $ git am --continue |
d19fbc3c BF |
1841 | ------------------------------------------------- |
1842 | ||
2de9b711 | 1843 | and Git will create the commit for you and continue applying the |
d19fbc3c BF |
1844 | remaining patches from the mailbox. |
1845 | ||
1846 | The final result will be a series of commits, one for each patch in | |
1847 | the original mailbox, with authorship and commit log message each | |
1848 | taken from the message containing each patch. | |
1849 | ||
eda69449 | 1850 | [[public-repositories]] |
2de9b711 | 1851 | Public Git repositories |
eda69449 | 1852 | ----------------------- |
d19fbc3c | 1853 | |
6e30fb0c DK |
1854 | Another way to submit changes to a project is to tell the maintainer |
1855 | of that project to pull the changes from your repository using | |
aa971cb9 | 1856 | linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull, |
6127c086 | 1857 | Getting updates with `git pull`>>" we described this as a way to get |
6e30fb0c DK |
1858 | updates from the "main" repository, but it works just as well in the |
1859 | other direction. | |
d19fbc3c | 1860 | |
eda69449 BF |
1861 | If you and the maintainer both have accounts on the same machine, then |
1862 | you can just pull changes from each other's repositories directly; | |
11d51533 | 1863 | commands that accept repository URLs as arguments will also accept a |
eda69449 | 1864 | local directory name: |
d19fbc3c BF |
1865 | |
1866 | ------------------------------------------------- | |
1867 | $ git clone /path/to/repository | |
1868 | $ git pull /path/to/other/repository | |
1869 | ------------------------------------------------- | |
1870 | ||
c9016158 | 1871 | or an ssh URL: |
11d51533 BF |
1872 | |
1873 | ------------------------------------------------- | |
1874 | $ git clone ssh://yourhost/~you/repository | |
1875 | ------------------------------------------------- | |
1876 | ||
1877 | For projects with few developers, or for synchronizing a few private | |
1878 | repositories, this may be all you need. | |
1879 | ||
eda69449 BF |
1880 | However, the more common way to do this is to maintain a separate public |
1881 | repository (usually on a different host) for others to pull changes | |
1882 | from. This is usually more convenient, and allows you to cleanly | |
1883 | separate private work in progress from publicly visible work. | |
d19fbc3c BF |
1884 | |
1885 | You will continue to do your day-to-day work in your personal | |
1886 | repository, but periodically "push" changes from your personal | |
1887 | repository into your public repository, allowing other developers to | |
1888 | pull from that repository. So the flow of changes, in a situation | |
1889 | where there is one other developer with a public repository, looks | |
1890 | like this: | |
1891 | ||
1892 | you push | |
1893 | your personal repo ------------------> your public repo | |
a6080a0a | 1894 | ^ | |
d19fbc3c BF |
1895 | | | |
1896 | | you pull | they pull | |
1897 | | | | |
1898 | | | | |
1899 | | they push V | |
1900 | their public repo <------------------- their repo | |
1901 | ||
11d51533 BF |
1902 | We explain how to do this in the following sections. |
1903 | ||
eda69449 BF |
1904 | [[setting-up-a-public-repository]] |
1905 | Setting up a public repository | |
1906 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1907 | ||
1249d8ad | 1908 | Assume your personal repository is in the directory `~/proj`. We |
6127c086 | 1909 | first create a new clone of the repository and tell `git daemon` that it |
eda69449 | 1910 | is meant to be public: |
d19fbc3c BF |
1911 | |
1912 | ------------------------------------------------- | |
52c80037 | 1913 | $ git clone --bare ~/proj proj.git |
eda69449 | 1914 | $ touch proj.git/git-daemon-export-ok |
d19fbc3c BF |
1915 | ------------------------------------------------- |
1916 | ||
52c80037 | 1917 | The resulting directory proj.git contains a "bare" git repository--it is |
1249d8ad | 1918 | just the contents of the `.git` directory, without any files checked out |
eda69449 | 1919 | around it. |
d19fbc3c | 1920 | |
1249d8ad | 1921 | Next, copy `proj.git` to the server where you plan to host the |
d19fbc3c BF |
1922 | public repository. You can use scp, rsync, or whatever is most |
1923 | convenient. | |
1924 | ||
eda69449 | 1925 | [[exporting-via-git]] |
2de9b711 | 1926 | Exporting a Git repository via the Git protocol |
eda69449 BF |
1927 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
1928 | ||
1929 | This is the preferred method. | |
1930 | ||
1931 | If someone else administers the server, they should tell you what | |
1249d8ad TK |
1932 | directory to put the repository in, and what `git://` URL it will |
1933 | appear at. You can then skip to the section | |
d19fbc3c BF |
1934 | "<<pushing-changes-to-a-public-repository,Pushing changes to a public |
1935 | repository>>", below. | |
1936 | ||
5162e697 | 1937 | Otherwise, all you need to do is start linkgit:git-daemon[1]; it will |
eda69449 | 1938 | listen on port 9418. By default, it will allow access to any directory |
2de9b711 | 1939 | that looks like a Git directory and contains the magic file |
6127c086 | 1940 | git-daemon-export-ok. Passing some directory paths as `git daemon` |
eda69449 BF |
1941 | arguments will further restrict the exports to those paths. |
1942 | ||
6127c086 | 1943 | You can also run `git daemon` as an inetd service; see the |
5162e697 | 1944 | linkgit:git-daemon[1] man page for details. (See especially the |
eda69449 | 1945 | examples section.) |
d19fbc3c BF |
1946 | |
1947 | [[exporting-via-http]] | |
de3f2c7b | 1948 | Exporting a git repository via HTTP |
eda69449 | 1949 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c | 1950 | |
2de9b711 | 1951 | The Git protocol gives better performance and reliability, but on a |
de3f2c7b | 1952 | host with a web server set up, HTTP exports may be simpler to set up. |
d19fbc3c | 1953 | |
2de9b711 | 1954 | All you need to do is place the newly created bare Git repository in |
d19fbc3c BF |
1955 | a directory that is exported by the web server, and make some |
1956 | adjustments to give web clients some extra information they need: | |
1957 | ||
1958 | ------------------------------------------------- | |
1959 | $ mv proj.git /home/you/public_html/proj.git | |
1960 | $ cd proj.git | |
c64415e2 | 1961 | $ git --bare update-server-info |
7dce9918 | 1962 | $ mv hooks/post-update.sample hooks/post-update |
d19fbc3c BF |
1963 | ------------------------------------------------- |
1964 | ||
1965 | (For an explanation of the last two lines, see | |
6998e4db | 1966 | linkgit:git-update-server-info[1] and linkgit:githooks[5].) |
d19fbc3c | 1967 | |
1249d8ad | 1968 | Advertise the URL of `proj.git`. Anybody else should then be able to |
c9016158 | 1969 | clone or pull from that URL, for example with a command line like: |
d19fbc3c BF |
1970 | |
1971 | ------------------------------------------------- | |
1972 | $ git clone http://yourserver.com/~you/proj.git | |
1973 | ------------------------------------------------- | |
1974 | ||
1975 | (See also | |
d5ff3b4b | 1976 | link:howto/setup-git-server-over-http.html[setup-git-server-over-http] |
d19fbc3c | 1977 | for a slightly more sophisticated setup using WebDAV which also |
de3f2c7b | 1978 | allows pushing over HTTP.) |
d19fbc3c | 1979 | |
d19fbc3c BF |
1980 | [[pushing-changes-to-a-public-repository]] |
1981 | Pushing changes to a public repository | |
eda69449 | 1982 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c | 1983 | |
eda69449 | 1984 | Note that the two techniques outlined above (exporting via |
d19fbc3c BF |
1985 | <<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other |
1986 | maintainers to fetch your latest changes, but they do not allow write | |
1987 | access, which you will need to update the public repository with the | |
1988 | latest changes created in your private repository. | |
1989 | ||
5162e697 | 1990 | The simplest way to do this is using linkgit:git-push[1] and ssh; to |
1249d8ad TK |
1991 | update the remote branch named `master` with the latest state of your |
1992 | branch named `master`, run | |
d19fbc3c BF |
1993 | |
1994 | ------------------------------------------------- | |
1995 | $ git push ssh://yourserver.com/~you/proj.git master:master | |
1996 | ------------------------------------------------- | |
1997 | ||
1998 | or just | |
1999 | ||
2000 | ------------------------------------------------- | |
2001 | $ git push ssh://yourserver.com/~you/proj.git master | |
2002 | ------------------------------------------------- | |
2003 | ||
6127c086 | 2004 | As with `git fetch`, `git push` will complain if this does not result in a |
a75d7b54 | 2005 | <<fast-forwards,fast-forward>>; see the following section for details on |
81eb417a | 2006 | handling this case. |
d19fbc3c | 2007 | |
1249d8ad | 2008 | Note that the target of a `push` is normally a |
11d51533 | 2009 | <<def_bare_repository,bare>> repository. You can also push to a |
d9be2485 TK |
2010 | repository that has a checked-out working tree, but a push to update the |
2011 | currently checked-out branch is denied by default to prevent confusion. | |
50995edd | 2012 | See the description of the receive.denyCurrentBranch option |
d9be2485 | 2013 | in linkgit:git-config[1] for details. |
11d51533 | 2014 | |
6127c086 | 2015 | As with `git fetch`, you may also set up configuration options to |
e9b49083 TK |
2016 | save typing; so, for example: |
2017 | ||
2018 | ------------------------------------------------- | |
2019 | $ git remote add public-repo ssh://yourserver.com/~you/proj.git | |
2020 | ------------------------------------------------- | |
2021 | ||
2022 | adds the following to `.git/config`: | |
d19fbc3c BF |
2023 | |
2024 | ------------------------------------------------- | |
d19fbc3c | 2025 | [remote "public-repo"] |
e9b49083 TK |
2026 | url = yourserver.com:proj.git |
2027 | fetch = +refs/heads/*:refs/remotes/example/* | |
d19fbc3c BF |
2028 | ------------------------------------------------- |
2029 | ||
e9b49083 | 2030 | which lets you do the same push with just |
d19fbc3c BF |
2031 | |
2032 | ------------------------------------------------- | |
2033 | $ git push public-repo master | |
2034 | ------------------------------------------------- | |
2035 | ||
1249d8ad TK |
2036 | See the explanations of the `remote.<name>.url`, |
2037 | `branch.<name>.remote`, and `remote.<name>.push` options in | |
2038 | linkgit:git-config[1] for details. | |
d19fbc3c | 2039 | |
81eb417a BF |
2040 | [[forcing-push]] |
2041 | What to do when a push fails | |
2042 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
2043 | ||
a75d7b54 | 2044 | If a push would not result in a <<fast-forwards,fast-forward>> of the |
81eb417a BF |
2045 | remote branch, then it will fail with an error like: |
2046 | ||
2047 | ------------------------------------------------- | |
2048 | error: remote 'refs/heads/master' is not an ancestor of | |
2049 | local 'refs/heads/master'. | |
2050 | Maybe you are not up-to-date and need to pull first? | |
2051 | error: failed to push to 'ssh://yourserver.com/~you/proj.git' | |
2052 | ------------------------------------------------- | |
2053 | ||
2054 | This can happen, for example, if you: | |
2055 | ||
6127c086 FC |
2056 | - use `git reset --hard` to remove already-published commits, or |
2057 | - use `git commit --amend` to replace already-published commits | |
7cb192ea | 2058 | (as in <<fixing-a-mistake-by-rewriting-history>>), or |
6127c086 | 2059 | - use `git rebase` to rebase any already-published commits (as |
81eb417a BF |
2060 | in <<using-git-rebase>>). |
2061 | ||
6127c086 | 2062 | You may force `git push` to perform the update anyway by preceding the |
81eb417a BF |
2063 | branch name with a plus sign: |
2064 | ||
2065 | ------------------------------------------------- | |
2066 | $ git push ssh://yourserver.com/~you/proj.git +master | |
2067 | ------------------------------------------------- | |
2068 | ||
d1471e06 TK |
2069 | Note the addition of the `+` sign. Alternatively, you can use the |
2070 | `-f` flag to force the remote update, as in: | |
2071 | ||
2072 | ------------------------------------------------- | |
2073 | $ git push -f ssh://yourserver.com/~you/proj.git master | |
2074 | ------------------------------------------------- | |
2075 | ||
81eb417a | 2076 | Normally whenever a branch head in a public repository is modified, it |
9e5d87d4 | 2077 | is modified to point to a descendant of the commit that it pointed to |
81eb417a | 2078 | before. By forcing a push in this situation, you break that convention. |
aa971cb9 | 2079 | (See <<problems-With-rewriting-history>>.) |
81eb417a BF |
2080 | |
2081 | Nevertheless, this is a common practice for people that need a simple | |
2082 | way to publish a work-in-progress patch series, and it is an acceptable | |
2083 | compromise as long as you warn other developers that this is how you | |
2084 | intend to manage the branch. | |
2085 | ||
2086 | It's also possible for a push to fail in this way when other people have | |
2087 | the right to push to the same repository. In that case, the correct | |
843c81dc EH |
2088 | solution is to retry the push after first updating your work: either by a |
2089 | pull, or by a fetch followed by a rebase; see the | |
81eb417a | 2090 | <<setting-up-a-shared-repository,next section>> and |
6998e4db | 2091 | linkgit:gitcvs-migration[7] for more. |
81eb417a | 2092 | |
e34caace | 2093 | [[setting-up-a-shared-repository]] |
d19fbc3c | 2094 | Setting up a shared repository |
eda69449 | 2095 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c BF |
2096 | |
2097 | Another way to collaborate is by using a model similar to that | |
2098 | commonly used in CVS, where several developers with special rights | |
2099 | all push to and pull from a single shared repository. See | |
6998e4db | 2100 | linkgit:gitcvs-migration[7] for instructions on how to |
d19fbc3c BF |
2101 | set this up. |
2102 | ||
2de9b711 | 2103 | However, while there is nothing wrong with Git's support for shared |
8fae2225 | 2104 | repositories, this mode of operation is not generally recommended, |
2de9b711 | 2105 | simply because the mode of collaboration that Git supports--by |
8fae2225 BF |
2106 | exchanging patches and pulling from public repositories--has so many |
2107 | advantages over the central shared repository: | |
2108 | ||
2109 | - Git's ability to quickly import and merge patches allows a | |
2110 | single maintainer to process incoming changes even at very | |
6127c086 | 2111 | high rates. And when that becomes too much, `git pull` provides |
8fae2225 BF |
2112 | an easy way for that maintainer to delegate this job to other |
2113 | maintainers while still allowing optional review of incoming | |
2114 | changes. | |
2115 | - Since every developer's repository has the same complete copy | |
2116 | of the project history, no repository is special, and it is | |
2117 | trivial for another developer to take over maintenance of a | |
2118 | project, either by mutual agreement, or because a maintainer | |
2119 | becomes unresponsive or difficult to work with. | |
2120 | - The lack of a central group of "committers" means there is | |
2121 | less need for formal decisions about who is "in" and who is | |
2122 | "out". | |
2123 | ||
e34caace | 2124 | [[setting-up-gitweb]] |
eda69449 BF |
2125 | Allowing web browsing of a repository |
2126 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 2127 | |
a8cd1402 | 2128 | The gitweb cgi script provides users an easy way to browse your |
2de9b711 TA |
2129 | project's files and history without having to install Git; see the file |
2130 | gitweb/INSTALL in the Git source tree for instructions on setting it up. | |
d19fbc3c | 2131 | |
e34caace | 2132 | [[sharing-development-examples]] |
b684f830 BF |
2133 | Examples |
2134 | -------- | |
d19fbc3c | 2135 | |
9e2163ea BF |
2136 | [[maintaining-topic-branches]] |
2137 | Maintaining topic branches for a Linux subsystem maintainer | |
2138 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
2139 | ||
2de9b711 | 2140 | This describes how Tony Luck uses Git in his role as maintainer of the |
9e2163ea BF |
2141 | IA64 architecture for the Linux kernel. |
2142 | ||
2143 | He uses two public branches: | |
2144 | ||
2145 | - A "test" tree into which patches are initially placed so that they | |
2146 | can get some exposure when integrated with other ongoing development. | |
2147 | This tree is available to Andrew for pulling into -mm whenever he | |
2148 | wants. | |
2149 | ||
2150 | - A "release" tree into which tested patches are moved for final sanity | |
2151 | checking, and as a vehicle to send them upstream to Linus (by sending | |
2152 | him a "please pull" request.) | |
2153 | ||
2154 | He also uses a set of temporary branches ("topic branches"), each | |
2155 | containing a logical grouping of patches. | |
2156 | ||
2157 | To set this up, first create your work tree by cloning Linus's public | |
2158 | tree: | |
2159 | ||
2160 | ------------------------------------------------- | |
283efb01 | 2161 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work |
9e2163ea BF |
2162 | $ cd work |
2163 | ------------------------------------------------- | |
2164 | ||
29b9a66f | 2165 | Linus's tree will be stored in the remote-tracking branch named origin/master, |
5162e697 DM |
2166 | and can be updated using linkgit:git-fetch[1]; you can track other |
2167 | public trees using linkgit:git-remote[1] to set up a "remote" and | |
2168 | linkgit:git-fetch[1] to keep them up-to-date; see | |
6e30fb0c | 2169 | <<repositories-and-branches>>. |
9e2163ea BF |
2170 | |
2171 | Now create the branches in which you are going to work; these start out | |
2172 | at the current tip of origin/master branch, and should be set up (using | |
1249d8ad | 2173 | the `--track` option to linkgit:git-branch[1]) to merge changes in from |
9e2163ea BF |
2174 | Linus by default. |
2175 | ||
2176 | ------------------------------------------------- | |
2177 | $ git branch --track test origin/master | |
2178 | $ git branch --track release origin/master | |
2179 | ------------------------------------------------- | |
2180 | ||
5162e697 | 2181 | These can be easily kept up to date using linkgit:git-pull[1]. |
9e2163ea BF |
2182 | |
2183 | ------------------------------------------------- | |
2184 | $ git checkout test && git pull | |
2185 | $ git checkout release && git pull | |
2186 | ------------------------------------------------- | |
2187 | ||
2188 | Important note! If you have any local changes in these branches, then | |
2189 | this merge will create a commit object in the history (with no local | |
2de9b711 | 2190 | changes Git will simply do a "fast-forward" merge). Many people dislike |
9e2163ea | 2191 | the "noise" that this creates in the Linux history, so you should avoid |
1249d8ad | 2192 | doing this capriciously in the `release` branch, as these noisy commits |
9e2163ea BF |
2193 | will become part of the permanent history when you ask Linus to pull |
2194 | from the release branch. | |
2195 | ||
5162e697 | 2196 | A few configuration variables (see linkgit:git-config[1]) can |
9e2163ea BF |
2197 | make it easy to push both branches to your public tree. (See |
2198 | <<setting-up-a-public-repository>>.) | |
2199 | ||
2200 | ------------------------------------------------- | |
2201 | $ cat >> .git/config <<EOF | |
2202 | [remote "mytree"] | |
283efb01 | 2203 | url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git |
9e2163ea BF |
2204 | push = release |
2205 | push = test | |
2206 | EOF | |
2207 | ------------------------------------------------- | |
2208 | ||
2209 | Then you can push both the test and release trees using | |
5162e697 | 2210 | linkgit:git-push[1]: |
9e2163ea BF |
2211 | |
2212 | ------------------------------------------------- | |
2213 | $ git push mytree | |
2214 | ------------------------------------------------- | |
2215 | ||
2216 | or push just one of the test and release branches using: | |
2217 | ||
2218 | ------------------------------------------------- | |
2219 | $ git push mytree test | |
2220 | ------------------------------------------------- | |
2221 | ||
2222 | or | |
2223 | ||
2224 | ------------------------------------------------- | |
2225 | $ git push mytree release | |
2226 | ------------------------------------------------- | |
2227 | ||
2228 | Now to apply some patches from the community. Think of a short | |
2229 | snappy name for a branch to hold this patch (or related group of | |
352953a5 TL |
2230 | patches), and create a new branch from a recent stable tag of |
2231 | Linus's branch. Picking a stable base for your branch will: | |
2232 | 1) help you: by avoiding inclusion of unrelated and perhaps lightly | |
2233 | tested changes | |
1249d8ad | 2234 | 2) help future bug hunters that use `git bisect` to find problems |
9e2163ea BF |
2235 | |
2236 | ------------------------------------------------- | |
352953a5 | 2237 | $ git checkout -b speed-up-spinlocks v2.6.35 |
9e2163ea BF |
2238 | ------------------------------------------------- |
2239 | ||
2240 | Now you apply the patch(es), run some tests, and commit the change(s). If | |
2241 | the patch is a multi-part series, then you should apply each as a separate | |
2242 | commit to this branch. | |
2243 | ||
2244 | ------------------------------------------------- | |
2245 | $ ... patch ... test ... commit [ ... patch ... test ... commit ]* | |
2246 | ------------------------------------------------- | |
2247 | ||
a7bdee11 | 2248 | When you are happy with the state of this change, you can merge it into the |
9e2163ea BF |
2249 | "test" branch in preparation to make it public: |
2250 | ||
2251 | ------------------------------------------------- | |
a7bdee11 | 2252 | $ git checkout test && git merge speed-up-spinlocks |
9e2163ea BF |
2253 | ------------------------------------------------- |
2254 | ||
2255 | It is unlikely that you would have any conflicts here ... but you might if you | |
2256 | spent a while on this step and had also pulled new versions from upstream. | |
2257 | ||
2258 | Some time later when enough time has passed and testing done, you can pull the | |
1249d8ad | 2259 | same branch into the `release` tree ready to go upstream. This is where you |
9e2163ea | 2260 | see the value of keeping each patch (or patch series) in its own branch. It |
1249d8ad | 2261 | means that the patches can be moved into the `release` tree in any order. |
9e2163ea BF |
2262 | |
2263 | ------------------------------------------------- | |
a7bdee11 | 2264 | $ git checkout release && git merge speed-up-spinlocks |
9e2163ea BF |
2265 | ------------------------------------------------- |
2266 | ||
2267 | After a while, you will have a number of branches, and despite the | |
2268 | well chosen names you picked for each of them, you may forget what | |
2269 | they are for, or what status they are in. To get a reminder of what | |
2270 | changes are in a specific branch, use: | |
2271 | ||
2272 | ------------------------------------------------- | |
467c0197 | 2273 | $ git log linux..branchname | git shortlog |
9e2163ea BF |
2274 | ------------------------------------------------- |
2275 | ||
06ada152 | 2276 | To see whether it has already been merged into the test or release branches, |
9e2163ea BF |
2277 | use: |
2278 | ||
2279 | ------------------------------------------------- | |
2280 | $ git log test..branchname | |
2281 | ------------------------------------------------- | |
2282 | ||
2283 | or | |
2284 | ||
2285 | ------------------------------------------------- | |
2286 | $ git log release..branchname | |
2287 | ------------------------------------------------- | |
2288 | ||
06ada152 | 2289 | (If this branch has not yet been merged, you will see some log entries. |
9e2163ea BF |
2290 | If it has been merged, then there will be no output.) |
2291 | ||
2292 | Once a patch completes the great cycle (moving from test to release, | |
2293 | then pulled by Linus, and finally coming back into your local | |
1249d8ad | 2294 | `origin/master` branch), the branch for this change is no longer needed. |
9e2163ea BF |
2295 | You detect this when the output from: |
2296 | ||
2297 | ------------------------------------------------- | |
2298 | $ git log origin..branchname | |
2299 | ------------------------------------------------- | |
2300 | ||
2301 | is empty. At this point the branch can be deleted: | |
2302 | ||
2303 | ------------------------------------------------- | |
2304 | $ git branch -d branchname | |
2305 | ------------------------------------------------- | |
2306 | ||
2307 | Some changes are so trivial that it is not necessary to create a separate | |
2308 | branch and then merge into each of the test and release branches. For | |
1249d8ad TK |
2309 | these changes, just apply directly to the `release` branch, and then |
2310 | merge that into the `test` branch. | |
9e2163ea | 2311 | |
ae6ef554 TK |
2312 | After pushing your work to `mytree`, you can use |
2313 | linkgit:git-request-pull[1] to prepare a "please pull" request message | |
2314 | to send to Linus: | |
9e2163ea BF |
2315 | |
2316 | ------------------------------------------------- | |
ae6ef554 TK |
2317 | $ git push mytree |
2318 | $ git request-pull origin mytree release | |
9e2163ea BF |
2319 | ------------------------------------------------- |
2320 | ||
2321 | Here are some of the scripts that simplify all this even further. | |
2322 | ||
2323 | ------------------------------------------------- | |
2324 | ==== update script ==== | |
48a8c26c | 2325 | # Update a branch in my Git tree. If the branch to be updated |
9e2163ea BF |
2326 | # is origin, then pull from kernel.org. Otherwise merge |
2327 | # origin/master branch into test|release branch | |
2328 | ||
2329 | case "$1" in | |
2330 | test|release) | |
2331 | git checkout $1 && git pull . origin | |
2332 | ;; | |
2333 | origin) | |
fc74ecc1 | 2334 | before=$(git rev-parse refs/remotes/origin/master) |
9e2163ea | 2335 | git fetch origin |
fc74ecc1 | 2336 | after=$(git rev-parse refs/remotes/origin/master) |
9e2163ea BF |
2337 | if [ $before != $after ] |
2338 | then | |
2339 | git log $before..$after | git shortlog | |
2340 | fi | |
2341 | ;; | |
2342 | *) | |
1a2ba8b9 | 2343 | echo "usage: $0 origin|test|release" 1>&2 |
9e2163ea BF |
2344 | exit 1 |
2345 | ;; | |
2346 | esac | |
2347 | ------------------------------------------------- | |
2348 | ||
2349 | ------------------------------------------------- | |
2350 | ==== merge script ==== | |
2351 | # Merge a branch into either the test or release branch | |
2352 | ||
2353 | pname=$0 | |
2354 | ||
2355 | usage() | |
2356 | { | |
1a2ba8b9 | 2357 | echo "usage: $pname branch test|release" 1>&2 |
9e2163ea BF |
2358 | exit 1 |
2359 | } | |
2360 | ||
fc74ecc1 | 2361 | git show-ref -q --verify -- refs/heads/"$1" || { |
9e2163ea BF |
2362 | echo "Can't see branch <$1>" 1>&2 |
2363 | usage | |
fc74ecc1 | 2364 | } |
9e2163ea BF |
2365 | |
2366 | case "$2" in | |
2367 | test|release) | |
2368 | if [ $(git log $2..$1 | wc -c) -eq 0 ] | |
2369 | then | |
2370 | echo $1 already merged into $2 1>&2 | |
2371 | exit 1 | |
2372 | fi | |
2373 | git checkout $2 && git pull . $1 | |
2374 | ;; | |
2375 | *) | |
2376 | usage | |
2377 | ;; | |
2378 | esac | |
2379 | ------------------------------------------------- | |
2380 | ||
2381 | ------------------------------------------------- | |
2382 | ==== status script ==== | |
48a8c26c | 2383 | # report on status of my ia64 Git tree |
9e2163ea BF |
2384 | |
2385 | gb=$(tput setab 2) | |
2386 | rb=$(tput setab 1) | |
2387 | restore=$(tput setab 9) | |
2388 | ||
2389 | if [ `git rev-list test..release | wc -c` -gt 0 ] | |
2390 | then | |
2391 | echo $rb Warning: commits in release that are not in test $restore | |
2392 | git log test..release | |
2393 | fi | |
2394 | ||
fc74ecc1 | 2395 | for branch in `git show-ref --heads | sed 's|^.*/||'` |
9e2163ea BF |
2396 | do |
2397 | if [ $branch = test -o $branch = release ] | |
2398 | then | |
2399 | continue | |
2400 | fi | |
2401 | ||
2402 | echo -n $gb ======= $branch ====== $restore " " | |
2403 | status= | |
2404 | for ref in test release origin/master | |
2405 | do | |
2406 | if [ `git rev-list $ref..$branch | wc -c` -gt 0 ] | |
2407 | then | |
2408 | status=$status${ref:0:1} | |
2409 | fi | |
2410 | done | |
2411 | case $status in | |
2412 | trl) | |
2413 | echo $rb Need to pull into test $restore | |
2414 | ;; | |
2415 | rl) | |
2416 | echo "In test" | |
2417 | ;; | |
2418 | l) | |
2419 | echo "Waiting for linus" | |
2420 | ;; | |
2421 | "") | |
2422 | echo $rb All done $restore | |
2423 | ;; | |
2424 | *) | |
2425 | echo $rb "<$status>" $restore | |
2426 | ;; | |
2427 | esac | |
2428 | git log origin/master..$branch | git shortlog | |
2429 | done | |
2430 | ------------------------------------------------- | |
d19fbc3c | 2431 | |
d19fbc3c | 2432 | |
d19fbc3c | 2433 | [[cleaning-up-history]] |
4c63ff45 BF |
2434 | Rewriting history and maintaining patch series |
2435 | ============================================== | |
2436 | ||
2437 | Normally commits are only added to a project, never taken away or | |
2438 | replaced. Git is designed with this assumption, and violating it will | |
2de9b711 | 2439 | cause Git's merge machinery (for example) to do the wrong thing. |
4c63ff45 BF |
2440 | |
2441 | However, there is a situation in which it can be useful to violate this | |
2442 | assumption. | |
2443 | ||
e34caace | 2444 | [[patch-series]] |
4c63ff45 BF |
2445 | Creating the perfect patch series |
2446 | --------------------------------- | |
2447 | ||
2448 | Suppose you are a contributor to a large project, and you want to add a | |
2449 | complicated feature, and to present it to the other developers in a way | |
2450 | that makes it easy for them to read your changes, verify that they are | |
2451 | correct, and understand why you made each change. | |
2452 | ||
b181d57f | 2453 | If you present all of your changes as a single patch (or commit), they |
79c96c57 | 2454 | may find that it is too much to digest all at once. |
4c63ff45 BF |
2455 | |
2456 | If you present them with the entire history of your work, complete with | |
2457 | mistakes, corrections, and dead ends, they may be overwhelmed. | |
2458 | ||
2459 | So the ideal is usually to produce a series of patches such that: | |
2460 | ||
2461 | 1. Each patch can be applied in order. | |
2462 | ||
2463 | 2. Each patch includes a single logical change, together with a | |
2464 | message explaining the change. | |
2465 | ||
2466 | 3. No patch introduces a regression: after applying any initial | |
2467 | part of the series, the resulting project still compiles and | |
2468 | works, and has no bugs that it didn't have before. | |
2469 | ||
2470 | 4. The complete series produces the same end result as your own | |
2471 | (probably much messier!) development process did. | |
2472 | ||
b181d57f BF |
2473 | We will introduce some tools that can help you do this, explain how to |
2474 | use them, and then explain some of the problems that can arise because | |
2475 | you are rewriting history. | |
4c63ff45 | 2476 | |
e34caace | 2477 | [[using-git-rebase]] |
6127c086 | 2478 | Keeping a patch series up to date using git rebase |
4c63ff45 BF |
2479 | -------------------------------------------------- |
2480 | ||
1249d8ad TK |
2481 | Suppose that you create a branch `mywork` on a remote-tracking branch |
2482 | `origin`, and create some commits on top of it: | |
4c63ff45 BF |
2483 | |
2484 | ------------------------------------------------- | |
2485 | $ git checkout -b mywork origin | |
2486 | $ vi file.txt | |
2487 | $ git commit | |
2488 | $ vi otherfile.txt | |
2489 | $ git commit | |
2490 | ... | |
2491 | ------------------------------------------------- | |
2492 | ||
2493 | You have performed no merges into mywork, so it is just a simple linear | |
1249d8ad | 2494 | sequence of patches on top of `origin`: |
4c63ff45 | 2495 | |
1dc71a91 | 2496 | ................................................ |
fa8347b8 | 2497 | o--o--O <-- origin |
4c63ff45 | 2498 | \ |
fa8347b8 | 2499 | a--b--c <-- mywork |
1dc71a91 | 2500 | ................................................ |
4c63ff45 BF |
2501 | |
2502 | Some more interesting work has been done in the upstream project, and | |
1249d8ad | 2503 | `origin` has advanced: |
4c63ff45 | 2504 | |
1dc71a91 | 2505 | ................................................ |
4c63ff45 BF |
2506 | o--o--O--o--o--o <-- origin |
2507 | \ | |
2508 | a--b--c <-- mywork | |
1dc71a91 | 2509 | ................................................ |
4c63ff45 | 2510 | |
1249d8ad | 2511 | At this point, you could use `pull` to merge your changes back in; |
4c63ff45 BF |
2512 | the result would create a new merge commit, like this: |
2513 | ||
1dc71a91 | 2514 | ................................................ |
4c63ff45 BF |
2515 | o--o--O--o--o--o <-- origin |
2516 | \ \ | |
2517 | a--b--c--m <-- mywork | |
1dc71a91 | 2518 | ................................................ |
a6080a0a | 2519 | |
4c63ff45 BF |
2520 | However, if you prefer to keep the history in mywork a simple series of |
2521 | commits without any merges, you may instead choose to use | |
5162e697 | 2522 | linkgit:git-rebase[1]: |
4c63ff45 BF |
2523 | |
2524 | ------------------------------------------------- | |
2525 | $ git checkout mywork | |
2526 | $ git rebase origin | |
2527 | ------------------------------------------------- | |
2528 | ||
b181d57f | 2529 | This will remove each of your commits from mywork, temporarily saving |
1249d8ad | 2530 | them as patches (in a directory named `.git/rebase-apply`), update mywork to |
b181d57f BF |
2531 | point at the latest version of origin, then apply each of the saved |
2532 | patches to the new mywork. The result will look like: | |
4c63ff45 BF |
2533 | |
2534 | ||
1dc71a91 | 2535 | ................................................ |
4c63ff45 BF |
2536 | o--o--O--o--o--o <-- origin |
2537 | \ | |
2538 | a'--b'--c' <-- mywork | |
1dc71a91 | 2539 | ................................................ |
4c63ff45 | 2540 | |
b181d57f | 2541 | In the process, it may discover conflicts. In that case it will stop |
6127c086 | 2542 | and allow you to fix the conflicts; after fixing conflicts, use `git add` |
7a7d4ef6 | 2543 | to update the index with those contents, and then, instead of |
6127c086 | 2544 | running `git commit`, just run |
4c63ff45 BF |
2545 | |
2546 | ------------------------------------------------- | |
2547 | $ git rebase --continue | |
2548 | ------------------------------------------------- | |
2549 | ||
2de9b711 | 2550 | and Git will continue applying the rest of the patches. |
4c63ff45 | 2551 | |
b6cbca38 | 2552 | At any point you may use the `--abort` option to abort this process and |
4c63ff45 BF |
2553 | return mywork to the state it had before you started the rebase: |
2554 | ||
2555 | ------------------------------------------------- | |
2556 | $ git rebase --abort | |
2557 | ------------------------------------------------- | |
2558 | ||
6c26bf4d TK |
2559 | If you need to reorder or edit a number of commits in a branch, it may |
2560 | be easier to use `git rebase -i`, which allows you to reorder and | |
2561 | squash commits, as well as marking them for individual editing during | |
2562 | the rebase. See <<interactive-rebase>> for details, and | |
2563 | <<reordering-patch-series>> for alternatives. | |
2564 | ||
7cb192ea BF |
2565 | [[rewriting-one-commit]] |
2566 | Rewriting a single commit | |
365aa199 BF |
2567 | ------------------------- |
2568 | ||
7cb192ea | 2569 | We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the |
365aa199 BF |
2570 | most recent commit using |
2571 | ||
2572 | ------------------------------------------------- | |
2573 | $ git commit --amend | |
2574 | ------------------------------------------------- | |
2575 | ||
2576 | which will replace the old commit by a new commit incorporating your | |
2577 | changes, giving you a chance to edit the old commit message first. | |
6c26bf4d TK |
2578 | This is useful for fixing typos in your last commit, or for adjusting |
2579 | the patch contents of a poorly staged commit. | |
365aa199 | 2580 | |
6c26bf4d TK |
2581 | If you need to amend commits from deeper in your history, you can |
2582 | use <<interactive-rebase,interactive rebase's `edit` instruction>>. | |
365aa199 | 2583 | |
6c26bf4d TK |
2584 | [[reordering-patch-series]] |
2585 | Reordering or selecting from a patch series | |
2586 | ------------------------------------------- | |
365aa199 | 2587 | |
6c26bf4d TK |
2588 | Sometimes you want to edit a commit deeper in your history. One |
2589 | approach is to use `git format-patch` to create a series of patches | |
2590 | and then reset the state to before the patches: | |
365aa199 BF |
2591 | |
2592 | ------------------------------------------------- | |
6c26bf4d TK |
2593 | $ git format-patch origin |
2594 | $ git reset --hard origin | |
365aa199 BF |
2595 | ------------------------------------------------- |
2596 | ||
6c26bf4d TK |
2597 | Then modify, reorder, or eliminate patches as needed before applying |
2598 | them again with linkgit:git-am[1]: | |
365aa199 BF |
2599 | |
2600 | ------------------------------------------------- | |
6c26bf4d | 2601 | $ git am *.patch |
365aa199 BF |
2602 | ------------------------------------------------- |
2603 | ||
6c26bf4d TK |
2604 | [[interactive-rebase]] |
2605 | Using interactive rebases | |
2606 | ------------------------- | |
365aa199 | 2607 | |
6c26bf4d TK |
2608 | You can also edit a patch series with an interactive rebase. This is |
2609 | the same as <<reordering-patch-series,reordering a patch series using | |
2610 | `format-patch`>>, so use whichever interface you like best. | |
4c63ff45 | 2611 | |
6c26bf4d TK |
2612 | Rebase your current HEAD on the last commit you want to retain as-is. |
2613 | For example, if you want to reorder the last 5 commits, use: | |
b181d57f BF |
2614 | |
2615 | ------------------------------------------------- | |
6c26bf4d | 2616 | $ git rebase -i HEAD~5 |
b181d57f BF |
2617 | ------------------------------------------------- |
2618 | ||
6c26bf4d TK |
2619 | This will open your editor with a list of steps to be taken to perform |
2620 | your rebase. | |
4c63ff45 | 2621 | |
b181d57f | 2622 | ------------------------------------------------- |
6c26bf4d TK |
2623 | pick deadbee The oneline of this commit |
2624 | pick fa1afe1 The oneline of the next commit | |
2625 | ... | |
4c63ff45 | 2626 | |
6c26bf4d TK |
2627 | # Rebase c0ffeee..deadbee onto c0ffeee |
2628 | # | |
2629 | # Commands: | |
2630 | # p, pick = use commit | |
2631 | # r, reword = use commit, but edit the commit message | |
2632 | # e, edit = use commit, but stop for amending | |
2633 | # s, squash = use commit, but meld into previous commit | |
2634 | # f, fixup = like "squash", but discard this commit's log message | |
2635 | # x, exec = run command (the rest of the line) using shell | |
2636 | # | |
2637 | # These lines can be re-ordered; they are executed from top to bottom. | |
2638 | # | |
2639 | # If you remove a line here THAT COMMIT WILL BE LOST. | |
2640 | # | |
2641 | # However, if you remove everything, the rebase will be aborted. | |
2642 | # | |
2643 | # Note that empty commits are commented out | |
2644 | ------------------------------------------------- | |
2645 | ||
2646 | As explained in the comments, you can reorder commits, squash them | |
2647 | together, edit commit messages, etc. by editing the list. Once you | |
2648 | are satisfied, save the list and close your editor, and the rebase | |
2649 | will begin. | |
2650 | ||
2651 | The rebase will stop where `pick` has been replaced with `edit` or | |
2652 | when a step in the list fails to mechanically resolve conflicts and | |
2653 | needs your help. When you are done editing and/or resolving conflicts | |
2654 | you can continue with `git rebase --continue`. If you decide that | |
2655 | things are getting too hairy, you can always bail out with `git rebase | |
2656 | --abort`. Even after the rebase is complete, you can still recover | |
2657 | the original branch by using the <<reflogs,reflog>>. | |
2658 | ||
2659 | For a more detailed discussion of the procedure and additional tips, | |
2660 | see the "INTERACTIVE MODE" section of linkgit:git-rebase[1]. | |
4c63ff45 | 2661 | |
e34caace | 2662 | [[patch-series-tools]] |
4c63ff45 BF |
2663 | Other tools |
2664 | ----------- | |
2665 | ||
73a1d050 | 2666 | There are numerous other tools, such as StGit, which exist for the |
79c96c57 | 2667 | purpose of maintaining a patch series. These are outside of the scope of |
b181d57f | 2668 | this manual. |
4c63ff45 | 2669 | |
aa971cb9 | 2670 | [[problems-With-rewriting-history]] |
4c63ff45 BF |
2671 | Problems with rewriting history |
2672 | ------------------------------- | |
2673 | ||
b181d57f BF |
2674 | The primary problem with rewriting the history of a branch has to do |
2675 | with merging. Suppose somebody fetches your branch and merges it into | |
2676 | their branch, with a result something like this: | |
2677 | ||
1dc71a91 | 2678 | ................................................ |
b181d57f BF |
2679 | o--o--O--o--o--o <-- origin |
2680 | \ \ | |
2681 | t--t--t--m <-- their branch: | |
1dc71a91 | 2682 | ................................................ |
b181d57f BF |
2683 | |
2684 | Then suppose you modify the last three commits: | |
2685 | ||
1dc71a91 | 2686 | ................................................ |
b181d57f BF |
2687 | o--o--o <-- new head of origin |
2688 | / | |
2689 | o--o--O--o--o--o <-- old head of origin | |
1dc71a91 | 2690 | ................................................ |
b181d57f BF |
2691 | |
2692 | If we examined all this history together in one repository, it will | |
2693 | look like: | |
2694 | ||
1dc71a91 | 2695 | ................................................ |
b181d57f BF |
2696 | o--o--o <-- new head of origin |
2697 | / | |
2698 | o--o--O--o--o--o <-- old head of origin | |
2699 | \ \ | |
2700 | t--t--t--m <-- their branch: | |
1dc71a91 | 2701 | ................................................ |
b181d57f BF |
2702 | |
2703 | Git has no way of knowing that the new head is an updated version of | |
2704 | the old head; it treats this situation exactly the same as it would if | |
2705 | two developers had independently done the work on the old and new heads | |
2706 | in parallel. At this point, if someone attempts to merge the new head | |
2de9b711 | 2707 | in to their branch, Git will attempt to merge together the two (old and |
b181d57f BF |
2708 | new) lines of development, instead of trying to replace the old by the |
2709 | new. The results are likely to be unexpected. | |
2710 | ||
2711 | You may still choose to publish branches whose history is rewritten, | |
2712 | and it may be useful for others to be able to fetch those branches in | |
2713 | order to examine or test them, but they should not attempt to pull such | |
2714 | branches into their own work. | |
2715 | ||
2716 | For true distributed development that supports proper merging, | |
2717 | published branches should never be rewritten. | |
2718 | ||
3fb00282 SP |
2719 | [[bisect-merges]] |
2720 | Why bisecting merge commits can be harder than bisecting linear history | |
2721 | ----------------------------------------------------------------------- | |
2722 | ||
5162e697 | 2723 | The linkgit:git-bisect[1] command correctly handles history that |
3fb00282 SP |
2724 | includes merge commits. However, when the commit that it finds is a |
2725 | merge commit, the user may need to work harder than usual to figure out | |
2726 | why that commit introduced a problem. | |
2727 | ||
2728 | Imagine this history: | |
2729 | ||
2730 | ................................................ | |
2731 | ---Z---o---X---...---o---A---C---D | |
2732 | \ / | |
2733 | o---o---Y---...---o---B | |
2734 | ................................................ | |
2735 | ||
2736 | Suppose that on the upper line of development, the meaning of one | |
2737 | of the functions that exists at Z is changed at commit X. The | |
2738 | commits from Z leading to A change both the function's | |
2739 | implementation and all calling sites that exist at Z, as well | |
2740 | as new calling sites they add, to be consistent. There is no | |
2741 | bug at A. | |
2742 | ||
2743 | Suppose that in the meantime on the lower line of development somebody | |
2744 | adds a new calling site for that function at commit Y. The | |
2745 | commits from Z leading to B all assume the old semantics of that | |
2746 | function and the callers and the callee are consistent with each | |
2747 | other. There is no bug at B, either. | |
2748 | ||
2749 | Suppose further that the two development lines merge cleanly at C, | |
2750 | so no conflict resolution is required. | |
2751 | ||
2752 | Nevertheless, the code at C is broken, because the callers added | |
2753 | on the lower line of development have not been converted to the new | |
2754 | semantics introduced on the upper line of development. So if all | |
2755 | you know is that D is bad, that Z is good, and that | |
5162e697 | 2756 | linkgit:git-bisect[1] identifies C as the culprit, how will you |
3fb00282 SP |
2757 | figure out that the problem is due to this change in semantics? |
2758 | ||
6127c086 | 2759 | When the result of a `git bisect` is a non-merge commit, you should |
3fb00282 SP |
2760 | normally be able to discover the problem by examining just that commit. |
2761 | Developers can make this easy by breaking their changes into small | |
2762 | self-contained commits. That won't help in the case above, however, | |
2763 | because the problem isn't obvious from examination of any single | |
2764 | commit; instead, a global view of the development is required. To | |
2765 | make matters worse, the change in semantics in the problematic | |
2766 | function may be just one small part of the changes in the upper | |
2767 | line of development. | |
2768 | ||
2769 | On the other hand, if instead of merging at C you had rebased the | |
2770 | history between Z to B on top of A, you would have gotten this | |
2771 | linear history: | |
2772 | ||
2773 | ................................................................ | |
2774 | ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D* | |
2775 | ................................................................ | |
2776 | ||
2777 | Bisecting between Z and D* would hit a single culprit commit Y*, | |
2778 | and understanding why Y* was broken would probably be easier. | |
2779 | ||
2de9b711 | 2780 | Partly for this reason, many experienced Git users, even when |
3fb00282 SP |
2781 | working on an otherwise merge-heavy project, keep the history |
2782 | linear by rebasing against the latest upstream version before | |
2783 | publishing. | |
2784 | ||
e34caace | 2785 | [[advanced-branch-management]] |
b181d57f BF |
2786 | Advanced branch management |
2787 | ========================== | |
4c63ff45 | 2788 | |
e34caace | 2789 | [[fetching-individual-branches]] |
b181d57f BF |
2790 | Fetching individual branches |
2791 | ---------------------------- | |
2792 | ||
5162e697 | 2793 | Instead of using linkgit:git-remote[1], you can also choose just |
b181d57f BF |
2794 | to update one branch at a time, and to store it locally under an |
2795 | arbitrary name: | |
2796 | ||
2797 | ------------------------------------------------- | |
2798 | $ git fetch origin todo:my-todo-work | |
2799 | ------------------------------------------------- | |
2800 | ||
1249d8ad | 2801 | The first argument, `origin`, just tells Git to fetch from the |
2de9b711 | 2802 | repository you originally cloned from. The second argument tells Git |
1249d8ad TK |
2803 | to fetch the branch named `todo` from the remote repository, and to |
2804 | store it locally under the name `refs/heads/my-todo-work`. | |
b181d57f BF |
2805 | |
2806 | You can also fetch branches from other repositories; so | |
2807 | ||
2808 | ------------------------------------------------- | |
2809 | $ git fetch git://example.com/proj.git master:example-master | |
2810 | ------------------------------------------------- | |
2811 | ||
1249d8ad TK |
2812 | will create a new branch named `example-master` and store in it the |
2813 | branch named `master` from the repository at the given URL. If you | |
b181d57f | 2814 | already have a branch named example-master, it will attempt to |
59723040 BF |
2815 | <<fast-forwards,fast-forward>> to the commit given by example.com's |
2816 | master branch. In more detail: | |
b181d57f | 2817 | |
59723040 BF |
2818 | [[fetch-fast-forwards]] |
2819 | git fetch and fast-forwards | |
2820 | --------------------------- | |
b181d57f | 2821 | |
1249d8ad | 2822 | In the previous example, when updating an existing branch, `git fetch` |
7a7d4ef6 | 2823 | checks to make sure that the most recent commit on the remote |
b181d57f BF |
2824 | branch is a descendant of the most recent commit on your copy of the |
2825 | branch before updating your copy of the branch to point at the new | |
a75d7b54 | 2826 | commit. Git calls this process a <<fast-forwards,fast-forward>>. |
b181d57f | 2827 | |
a75d7b54 | 2828 | A fast-forward looks something like this: |
b181d57f | 2829 | |
1dc71a91 | 2830 | ................................................ |
b181d57f BF |
2831 | o--o--o--o <-- old head of the branch |
2832 | \ | |
2833 | o--o--o <-- new head of the branch | |
1dc71a91 | 2834 | ................................................ |
b181d57f BF |
2835 | |
2836 | ||
2837 | In some cases it is possible that the new head will *not* actually be | |
2838 | a descendant of the old head. For example, the developer may have | |
2839 | realized she made a serious mistake, and decided to backtrack, | |
2840 | resulting in a situation like: | |
2841 | ||
1dc71a91 | 2842 | ................................................ |
b181d57f BF |
2843 | o--o--o--o--a--b <-- old head of the branch |
2844 | \ | |
2845 | o--o--o <-- new head of the branch | |
1dc71a91 | 2846 | ................................................ |
b181d57f | 2847 | |
1249d8ad | 2848 | In this case, `git fetch` will fail, and print out a warning. |
b181d57f | 2849 | |
2de9b711 | 2850 | In that case, you can still force Git to update to the new head, as |
b181d57f | 2851 | described in the following section. However, note that in the |
1249d8ad | 2852 | situation above this may mean losing the commits labeled `a` and `b`, |
b181d57f BF |
2853 | unless you've already created a reference of your own pointing to |
2854 | them. | |
2855 | ||
e34caace | 2856 | [[forcing-fetch]] |
6127c086 | 2857 | Forcing git fetch to do non-fast-forward updates |
b181d57f BF |
2858 | ------------------------------------------------ |
2859 | ||
2860 | If git fetch fails because the new head of a branch is not a | |
2861 | descendant of the old head, you may force the update with: | |
2862 | ||
2863 | ------------------------------------------------- | |
2864 | $ git fetch git://example.com/proj.git +master:refs/remotes/example/master | |
2865 | ------------------------------------------------- | |
2866 | ||
1249d8ad | 2867 | Note the addition of the `+` sign. Alternatively, you can use the `-f` |
c64415e2 BF |
2868 | flag to force updates of all the fetched branches, as in: |
2869 | ||
2870 | ------------------------------------------------- | |
2871 | $ git fetch -f origin | |
2872 | ------------------------------------------------- | |
2873 | ||
2874 | Be aware that commits that the old version of example/master pointed at | |
2875 | may be lost, as we saw in the previous section. | |
b181d57f | 2876 | |
e34caace | 2877 | [[remote-branch-configuration]] |
29b9a66f MM |
2878 | Configuring remote-tracking branches |
2879 | ------------------------------------ | |
b181d57f | 2880 | |
1249d8ad | 2881 | We saw above that `origin` is just a shortcut to refer to the |
79c96c57 | 2882 | repository that you originally cloned from. This information is |
2de9b711 | 2883 | stored in Git configuration variables, which you can see using |
5162e697 | 2884 | linkgit:git-config[1]: |
b181d57f BF |
2885 | |
2886 | ------------------------------------------------- | |
9d13bda3 | 2887 | $ git config -l |
b181d57f BF |
2888 | core.repositoryformatversion=0 |
2889 | core.filemode=true | |
2890 | core.logallrefupdates=true | |
2891 | remote.origin.url=git://git.kernel.org/pub/scm/git/git.git | |
2892 | remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* | |
2893 | branch.master.remote=origin | |
2894 | branch.master.merge=refs/heads/master | |
2895 | ------------------------------------------------- | |
2896 | ||
2897 | If there are other repositories that you also use frequently, you can | |
2898 | create similar configuration options to save typing; for example, | |
b181d57f BF |
2899 | |
2900 | ------------------------------------------------- | |
47adb8ac | 2901 | $ git remote add example git://example.com/proj.git |
b181d57f BF |
2902 | ------------------------------------------------- |
2903 | ||
47adb8ac | 2904 | adds the following to `.git/config`: |
b181d57f BF |
2905 | |
2906 | ------------------------------------------------- | |
47adb8ac TK |
2907 | [remote "example"] |
2908 | url = git://example.com/proj.git | |
2909 | fetch = +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2910 | ------------------------------------------------- |
2911 | ||
47adb8ac TK |
2912 | Also note that the above configuration can be performed by directly |
2913 | editing the file `.git/config` instead of using linkgit:git-remote[1]. | |
b181d57f | 2914 | |
47adb8ac TK |
2915 | After configuring the remote, the following three commands will do the |
2916 | same thing: | |
b181d57f BF |
2917 | |
2918 | ------------------------------------------------- | |
47adb8ac TK |
2919 | $ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/* |
2920 | $ git fetch example +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2921 | $ git fetch example |
2922 | ------------------------------------------------- | |
2923 | ||
5162e697 | 2924 | See linkgit:git-config[1] for more details on the configuration |
47adb8ac TK |
2925 | options mentioned above and linkgit:git-fetch[1] for more details on |
2926 | the refspec syntax. | |
d19fbc3c | 2927 | |
d19fbc3c | 2928 | |
036f8199 BF |
2929 | [[git-concepts]] |
2930 | Git concepts | |
2931 | ============ | |
d19fbc3c | 2932 | |
036f8199 BF |
2933 | Git is built on a small number of simple but powerful ideas. While it |
2934 | is possible to get things done without understanding them, you will find | |
2de9b711 | 2935 | Git much more intuitive if you do. |
036f8199 BF |
2936 | |
2937 | We start with the most important, the <<def_object_database,object | |
2938 | database>> and the <<def_index,index>>. | |
b181d57f | 2939 | |
e34caace | 2940 | [[the-object-database]] |
b181d57f BF |
2941 | The Object Database |
2942 | ------------------- | |
2943 | ||
1bbf1c79 BF |
2944 | |
2945 | We already saw in <<understanding-commits>> that all commits are stored | |
2946 | under a 40-digit "object name". In fact, all the information needed to | |
2947 | represent the history of a project is stored in objects with such names. | |
a6e5ef7d FC |
2948 | In each case the name is calculated by taking the SHA-1 hash of the |
2949 | contents of the object. The SHA-1 hash is a cryptographic hash function. | |
1bbf1c79 BF |
2950 | What that means to us is that it is impossible to find two different |
2951 | objects with the same name. This has a number of advantages; among | |
2952 | others: | |
2953 | ||
2954 | - Git can quickly determine whether two objects are identical or not, | |
2955 | just by comparing names. | |
06ada152 | 2956 | - Since object names are computed the same way in every repository, the |
1bbf1c79 BF |
2957 | same content stored in two repositories will always be stored under |
2958 | the same name. | |
2959 | - Git can detect errors when it reads an object, by checking that the | |
a6e5ef7d | 2960 | object's name is still the SHA-1 hash of its contents. |
1bbf1c79 BF |
2961 | |
2962 | (See <<object-details>> for the details of the object formatting and | |
a6e5ef7d | 2963 | SHA-1 calculation.) |
1bbf1c79 BF |
2964 | |
2965 | There are four different types of objects: "blob", "tree", "commit", and | |
2966 | "tag". | |
2967 | ||
2968 | - A <<def_blob_object,"blob" object>> is used to store file data. | |
843c81dc | 2969 | - A <<def_tree_object,"tree" object>> ties one or more |
1bbf1c79 BF |
2970 | "blob" objects into a directory structure. In addition, a tree object |
2971 | can refer to other tree objects, thus creating a directory hierarchy. | |
2972 | - A <<def_commit_object,"commit" object>> ties such directory hierarchies | |
2ef8ac1b | 2973 | together into a <<def_DAG,directed acyclic graph>> of revisions--each |
1bbf1c79 BF |
2974 | commit contains the object name of exactly one tree designating the |
2975 | directory hierarchy at the time of the commit. In addition, a commit | |
2976 | refers to "parent" commit objects that describe the history of how we | |
2977 | arrived at that directory hierarchy. | |
2978 | - A <<def_tag_object,"tag" object>> symbolically identifies and can be | |
2979 | used to sign other objects. It contains the object name and type of | |
2980 | another object, a symbolic name (of course!) and, optionally, a | |
2981 | signature. | |
b181d57f | 2982 | |
b181d57f BF |
2983 | The object types in some more detail: |
2984 | ||
513d419c BF |
2985 | [[commit-object]] |
2986 | Commit Object | |
2987 | ~~~~~~~~~~~~~ | |
b181d57f | 2988 | |
1bbf1c79 | 2989 | The "commit" object links a physical state of a tree with a description |
1249d8ad | 2990 | of how we got there and why. Use the `--pretty=raw` option to |
5162e697 | 2991 | linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite |
1bbf1c79 BF |
2992 | commit: |
2993 | ||
2994 | ------------------------------------------------ | |
2995 | $ git show -s --pretty=raw 2be7fcb476 | |
2996 | commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4 | |
2997 | tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf | |
2998 | parent 257a84d9d02e90447b149af58b271c19405edb6a | |
2999 | author Dave Watson <dwatson@mimvista.com> 1187576872 -0400 | |
3000 | committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700 | |
3001 | ||
3002 | Fix misspelling of 'suppress' in docs | |
3003 | ||
3004 | Signed-off-by: Junio C Hamano <gitster@pobox.com> | |
3005 | ------------------------------------------------ | |
3006 | ||
3007 | As you can see, a commit is defined by: | |
3008 | ||
a6e5ef7d | 3009 | - a tree: The SHA-1 name of a tree object (as defined below), representing |
1bbf1c79 | 3010 | the contents of a directory at a certain point in time. |
edfbbf7e | 3011 | - parent(s): The SHA-1 name(s) of some number of commits which represent the |
9e5d87d4 | 3012 | immediately previous step(s) in the history of the project. The |
1bbf1c79 BF |
3013 | example above has one parent; merge commits may have more than |
3014 | one. A commit with no parents is called a "root" commit, and | |
3015 | represents the initial revision of a project. Each project must have | |
3016 | at least one root. A project can also have multiple roots, though | |
3017 | that isn't common (or necessarily a good idea). | |
3018 | - an author: The name of the person responsible for this change, together | |
3019 | with its date. | |
3020 | - a committer: The name of the person who actually created the commit, | |
3021 | with the date it was done. This may be different from the author, for | |
3022 | example, if the author was someone who wrote a patch and emailed it | |
3023 | to the person who used it to create the commit. | |
3024 | - a comment describing this commit. | |
3025 | ||
3026 | Note that a commit does not itself contain any information about what | |
3027 | actually changed; all changes are calculated by comparing the contents | |
3028 | of the tree referred to by this commit with the trees associated with | |
2de9b711 | 3029 | its parents. In particular, Git does not attempt to record file renames |
1bbf1c79 BF |
3030 | explicitly, though it can identify cases where the existence of the same |
3031 | file data at changing paths suggests a rename. (See, for example, the | |
1249d8ad | 3032 | `-M` option to linkgit:git-diff[1]). |
1bbf1c79 | 3033 | |
5162e697 | 3034 | A commit is usually created by linkgit:git-commit[1], which creates a |
1bbf1c79 BF |
3035 | commit whose parent is normally the current HEAD, and whose tree is |
3036 | taken from the content currently stored in the index. | |
b181d57f | 3037 | |
e34caace | 3038 | [[tree-object]] |
b181d57f | 3039 | Tree Object |
971aa71f | 3040 | ~~~~~~~~~~~ |
b181d57f | 3041 | |
5162e697 DM |
3042 | The ever-versatile linkgit:git-show[1] command can also be used to |
3043 | examine tree objects, but linkgit:git-ls-tree[1] will give you more | |
1bbf1c79 BF |
3044 | details: |
3045 | ||
3046 | ------------------------------------------------ | |
3047 | $ git ls-tree fb3a8bdd0ce | |
3048 | 100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore | |
3049 | 100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap | |
3050 | 100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING | |
3051 | 040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation | |
3052 | 100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN | |
3053 | 100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL | |
3054 | 100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile | |
3055 | 100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README | |
3056 | ... | |
3057 | ------------------------------------------------ | |
3058 | ||
3059 | As you can see, a tree object contains a list of entries, each with a | |
a6e5ef7d | 3060 | mode, object type, SHA-1 name, and name, sorted by name. It represents |
1bbf1c79 BF |
3061 | the contents of a single directory tree. |
3062 | ||
3063 | The object type may be a blob, representing the contents of a file, or | |
3064 | another tree, representing the contents of a subdirectory. Since trees | |
a6e5ef7d FC |
3065 | and blobs, like all other objects, are named by the SHA-1 hash of their |
3066 | contents, two trees have the same SHA-1 name if and only if their | |
1bbf1c79 | 3067 | contents (including, recursively, the contents of all subdirectories) |
2de9b711 | 3068 | are identical. This allows Git to quickly determine the differences |
1bbf1c79 BF |
3069 | between two related tree objects, since it can ignore any entries with |
3070 | identical object names. | |
3071 | ||
3072 | (Note: in the presence of submodules, trees may also have commits as | |
6dd14366 | 3073 | entries. See <<submodules>> for documentation.) |
1bbf1c79 | 3074 | |
2de9b711 | 3075 | Note that the files all have mode 644 or 755: Git actually only pays |
1bbf1c79 | 3076 | attention to the executable bit. |
b181d57f | 3077 | |
513d419c BF |
3078 | [[blob-object]] |
3079 | Blob Object | |
3080 | ~~~~~~~~~~~ | |
b181d57f | 3081 | |
5162e697 | 3082 | You can use linkgit:git-show[1] to examine the contents of a blob; take, |
1249d8ad | 3083 | for example, the blob in the entry for `COPYING` from the tree above: |
b181d57f | 3084 | |
1bbf1c79 BF |
3085 | ------------------------------------------------ |
3086 | $ git show 6ff87c4664 | |
3087 | ||
3088 | Note that the only valid version of the GPL as far as this project | |
3089 | is concerned is _this_ particular version of the license (ie v2, not | |
3090 | v2.2 or v3.x or whatever), unless explicitly otherwise stated. | |
3091 | ... | |
3092 | ------------------------------------------------ | |
b181d57f | 3093 | |
1bbf1c79 BF |
3094 | A "blob" object is nothing but a binary blob of data. It doesn't refer |
3095 | to anything else or have attributes of any kind. | |
3096 | ||
3097 | Since the blob is entirely defined by its data, if two files in a | |
3098 | directory tree (or in multiple different versions of the repository) | |
3099 | have the same contents, they will share the same blob object. The object | |
3100 | is totally independent of its location in the directory tree, and | |
3101 | renaming a file does not change the object that file is associated with. | |
3102 | ||
3103 | Note that any tree or blob object can be examined using | |
5162e697 | 3104 | linkgit:git-show[1] with the <revision>:<path> syntax. This can |
1bbf1c79 BF |
3105 | sometimes be useful for browsing the contents of a tree that is not |
3106 | currently checked out. | |
b181d57f | 3107 | |
e34caace | 3108 | [[trust]] |
b181d57f | 3109 | Trust |
971aa71f | 3110 | ~~~~~ |
b181d57f | 3111 | |
a6e5ef7d | 3112 | If you receive the SHA-1 name of a blob from one source, and its contents |
1bbf1c79 | 3113 | from another (possibly untrusted) source, you can still trust that those |
a6e5ef7d FC |
3114 | contents are correct as long as the SHA-1 name agrees. This is because |
3115 | the SHA-1 is designed so that it is infeasible to find different contents | |
1bbf1c79 | 3116 | that produce the same hash. |
b181d57f | 3117 | |
a6e5ef7d | 3118 | Similarly, you need only trust the SHA-1 name of a top-level tree object |
1bbf1c79 | 3119 | to trust the contents of the entire directory that it refers to, and if |
a6e5ef7d | 3120 | you receive the SHA-1 name of a commit from a trusted source, then you |
1bbf1c79 BF |
3121 | can easily verify the entire history of commits reachable through |
3122 | parents of that commit, and all of those contents of the trees referred | |
3123 | to by those commits. | |
b181d57f BF |
3124 | |
3125 | So to introduce some real trust in the system, the only thing you need | |
3126 | to do is to digitally sign just 'one' special note, which includes the | |
3127 | name of a top-level commit. Your digital signature shows others | |
3128 | that you trust that commit, and the immutability of the history of | |
3129 | commits tells others that they can trust the whole history. | |
3130 | ||
3131 | In other words, you can easily validate a whole archive by just | |
a6e5ef7d | 3132 | sending out a single email that tells the people the name (SHA-1 hash) |
b181d57f BF |
3133 | of the top commit, and digitally sign that email using something |
3134 | like GPG/PGP. | |
3135 | ||
2de9b711 | 3136 | To assist in this, Git also provides the tag object... |
b181d57f | 3137 | |
e34caace | 3138 | [[tag-object]] |
b181d57f | 3139 | Tag Object |
971aa71f | 3140 | ~~~~~~~~~~ |
b181d57f | 3141 | |
1bbf1c79 BF |
3142 | A tag object contains an object, object type, tag name, the name of the |
3143 | person ("tagger") who created the tag, and a message, which may contain | |
843c81dc | 3144 | a signature, as can be seen using linkgit:git-cat-file[1]: |
b181d57f | 3145 | |
1bbf1c79 BF |
3146 | ------------------------------------------------ |
3147 | $ git cat-file tag v1.5.0 | |
3148 | object 437b1b20df4b356c9342dac8d38849f24ef44f27 | |
3149 | type commit | |
3150 | tag v1.5.0 | |
3151 | tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000 | |
3152 | ||
3153 | GIT 1.5.0 | |
3154 | -----BEGIN PGP SIGNATURE----- | |
3155 | Version: GnuPG v1.4.6 (GNU/Linux) | |
3156 | ||
3157 | iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui | |
3158 | nLE/L9aUXdWeTFPron96DLA= | |
3159 | =2E+0 | |
3160 | -----END PGP SIGNATURE----- | |
3161 | ------------------------------------------------ | |
b181d57f | 3162 | |
5162e697 DM |
3163 | See the linkgit:git-tag[1] command to learn how to create and verify tag |
3164 | objects. (Note that linkgit:git-tag[1] can also be used to create | |
1bbf1c79 | 3165 | "lightweight tags", which are not tag objects at all, but just simple |
1249d8ad | 3166 | references whose names begin with `refs/tags/`). |
b181d57f | 3167 | |
09eff7b0 | 3168 | [[pack-files]] |
2de9b711 | 3169 | How Git stores objects efficiently: pack files |
09eff7b0 BF |
3170 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
3171 | ||
9644ffdd | 3172 | Newly created objects are initially created in a file named after the |
1249d8ad | 3173 | object's SHA-1 hash (stored in `.git/objects`). |
09eff7b0 BF |
3174 | |
3175 | Unfortunately this system becomes inefficient once a project has a | |
3176 | lot of objects. Try this on an old project: | |
3177 | ||
3178 | ------------------------------------------------ | |
3179 | $ git count-objects | |
3180 | 6930 objects, 47620 kilobytes | |
3181 | ------------------------------------------------ | |
3182 | ||
3183 | The first number is the number of objects which are kept in | |
3184 | individual files. The second is the amount of space taken up by | |
3185 | those "loose" objects. | |
3186 | ||
2de9b711 | 3187 | You can save space and make Git faster by moving these loose objects in |
09eff7b0 BF |
3188 | to a "pack file", which stores a group of objects in an efficient |
3189 | compressed format; the details of how pack files are formatted can be | |
d5ff3b4b | 3190 | found in link:technical/pack-format.html[pack format]. |
09eff7b0 BF |
3191 | |
3192 | To put the loose objects into a pack, just run git repack: | |
3193 | ||
3194 | ------------------------------------------------ | |
3195 | $ git repack | |
3e65ac49 TA |
3196 | Counting objects: 6020, done. |
3197 | Delta compression using up to 4 threads. | |
3198 | Compressing objects: 100% (6020/6020), done. | |
3199 | Writing objects: 100% (6020/6020), done. | |
3200 | Total 6020 (delta 4070), reused 0 (delta 0) | |
09eff7b0 BF |
3201 | ------------------------------------------------ |
3202 | ||
3e65ac49 TA |
3203 | This creates a single "pack file" in .git/objects/pack/ |
3204 | containing all currently unpacked objects. You can then run | |
09eff7b0 BF |
3205 | |
3206 | ------------------------------------------------ | |
3207 | $ git prune | |
3208 | ------------------------------------------------ | |
3209 | ||
3210 | to remove any of the "loose" objects that are now contained in the | |
3211 | pack. This will also remove any unreferenced objects (which may be | |
1249d8ad | 3212 | created when, for example, you use `git reset` to remove a commit). |
09eff7b0 | 3213 | You can verify that the loose objects are gone by looking at the |
1249d8ad | 3214 | `.git/objects` directory or by running |
09eff7b0 BF |
3215 | |
3216 | ------------------------------------------------ | |
3217 | $ git count-objects | |
3218 | 0 objects, 0 kilobytes | |
3219 | ------------------------------------------------ | |
3220 | ||
3221 | Although the object files are gone, any commands that refer to those | |
3222 | objects will work exactly as they did before. | |
3223 | ||
5162e697 | 3224 | The linkgit:git-gc[1] command performs packing, pruning, and more for |
09eff7b0 BF |
3225 | you, so is normally the only high-level command you need. |
3226 | ||
3227 | [[dangling-objects]] | |
3228 | Dangling objects | |
3229 | ~~~~~~~~~~~~~~~~ | |
3230 | ||
5162e697 | 3231 | The linkgit:git-fsck[1] command will sometimes complain about dangling |
09eff7b0 BF |
3232 | objects. They are not a problem. |
3233 | ||
3234 | The most common cause of dangling objects is that you've rebased a | |
3235 | branch, or you have pulled from somebody else who rebased a branch--see | |
3236 | <<cleaning-up-history>>. In that case, the old head of the original | |
3237 | branch still exists, as does everything it pointed to. The branch | |
3238 | pointer itself just doesn't, since you replaced it with another one. | |
3239 | ||
3240 | There are also other situations that cause dangling objects. For | |
1249d8ad | 3241 | example, a "dangling blob" may arise because you did a `git add` of a |
09eff7b0 BF |
3242 | file, but then, before you actually committed it and made it part of the |
3243 | bigger picture, you changed something else in that file and committed | |
2ef8ac1b | 3244 | that *updated* thing--the old state that you added originally ends up |
09eff7b0 BF |
3245 | not being pointed to by any commit or tree, so it's now a dangling blob |
3246 | object. | |
3247 | ||
3248 | Similarly, when the "recursive" merge strategy runs, and finds that | |
3249 | there are criss-cross merges and thus more than one merge base (which is | |
3250 | fairly unusual, but it does happen), it will generate one temporary | |
3251 | midway tree (or possibly even more, if you had lots of criss-crossing | |
3252 | merges and more than two merge bases) as a temporary internal merge | |
3253 | base, and again, those are real objects, but the end result will not end | |
3254 | up pointing to them, so they end up "dangling" in your repository. | |
3255 | ||
3256 | Generally, dangling objects aren't anything to worry about. They can | |
3257 | even be very useful: if you screw something up, the dangling objects can | |
3258 | be how you recover your old tree (say, you did a rebase, and realized | |
2ef8ac1b | 3259 | that you really didn't want to--you can look at what dangling objects |
09eff7b0 BF |
3260 | you have, and decide to reset your head to some old dangling state). |
3261 | ||
3262 | For commits, you can just use: | |
3263 | ||
3264 | ------------------------------------------------ | |
3265 | $ gitk <dangling-commit-sha-goes-here> --not --all | |
3266 | ------------------------------------------------ | |
3267 | ||
3268 | This asks for all the history reachable from the given commit but not | |
3269 | from any branch, tag, or other reference. If you decide it's something | |
3270 | you want, you can always create a new reference to it, e.g., | |
3271 | ||
3272 | ------------------------------------------------ | |
3273 | $ git branch recovered-branch <dangling-commit-sha-goes-here> | |
3274 | ------------------------------------------------ | |
3275 | ||
3276 | For blobs and trees, you can't do the same, but you can still examine | |
3277 | them. You can just do | |
3278 | ||
3279 | ------------------------------------------------ | |
3280 | $ git show <dangling-blob/tree-sha-goes-here> | |
3281 | ------------------------------------------------ | |
3282 | ||
3283 | to show what the contents of the blob were (or, for a tree, basically | |
1249d8ad | 3284 | what the `ls` for that directory was), and that may give you some idea |
09eff7b0 BF |
3285 | of what the operation was that left that dangling object. |
3286 | ||
3287 | Usually, dangling blobs and trees aren't very interesting. They're | |
3288 | almost always the result of either being a half-way mergebase (the blob | |
3289 | will often even have the conflict markers from a merge in it, if you | |
3290 | have had conflicting merges that you fixed up by hand), or simply | |
1249d8ad | 3291 | because you interrupted a `git fetch` with ^C or something like that, |
09eff7b0 BF |
3292 | leaving _some_ of the new objects in the object database, but just |
3293 | dangling and useless. | |
3294 | ||
3295 | Anyway, once you are sure that you're not interested in any dangling | |
3296 | state, you can just prune all unreachable objects: | |
3297 | ||
3298 | ------------------------------------------------ | |
3299 | $ git prune | |
3300 | ------------------------------------------------ | |
3301 | ||
ddeb817f | 3302 | and they'll be gone. (You should only run `git prune` on a quiescent |
2ef8ac1b | 3303 | repository--it's kind of like doing a filesystem fsck recovery: you |
09eff7b0 | 3304 | don't want to do that while the filesystem is mounted. |
ddeb817f TA |
3305 | `git prune` is designed not to cause any harm in such cases of concurrent |
3306 | accesses to a repository but you might receive confusing or scary messages.) | |
b181d57f | 3307 | |
1cdade2c BF |
3308 | [[recovering-from-repository-corruption]] |
3309 | Recovering from repository corruption | |
3310 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3311 | ||
2de9b711 TA |
3312 | By design, Git treats data trusted to it with caution. However, even in |
3313 | the absence of bugs in Git itself, it is still possible that hardware or | |
1cdade2c BF |
3314 | operating system errors could corrupt data. |
3315 | ||
3316 | The first defense against such problems is backups. You can back up a | |
2de9b711 | 3317 | Git directory using clone, or just using cp, tar, or any other backup |
1cdade2c BF |
3318 | mechanism. |
3319 | ||
3320 | As a last resort, you can search for the corrupted objects and attempt | |
3321 | to replace them by hand. Back up your repository before attempting this | |
3322 | in case you corrupt things even more in the process. | |
3323 | ||
3324 | We'll assume that the problem is a single missing or corrupted blob, | |
9e5d87d4 | 3325 | which is sometimes a solvable problem. (Recovering missing trees and |
1cdade2c BF |
3326 | especially commits is *much* harder). |
3327 | ||
3328 | Before starting, verify that there is corruption, and figure out where | |
5162e697 | 3329 | it is with linkgit:git-fsck[1]; this may be time-consuming. |
1cdade2c BF |
3330 | |
3331 | Assume the output looks like this: | |
3332 | ||
3333 | ------------------------------------------------ | |
c6a13b2c | 3334 | $ git fsck --full --no-dangling |
1cdade2c BF |
3335 | broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 |
3336 | to blob 4b9458b3786228369c63936db65827de3cc06200 | |
3337 | missing blob 4b9458b3786228369c63936db65827de3cc06200 | |
3338 | ------------------------------------------------ | |
3339 | ||
1cdade2c BF |
3340 | Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6 |
3341 | points to it. If you could find just one copy of that missing blob | |
3342 | object, possibly in some other repository, you could move it into | |
1249d8ad | 3343 | `.git/objects/4b/9458b3...` and be done. Suppose you can't. You can |
5162e697 | 3344 | still examine the tree that pointed to it with linkgit:git-ls-tree[1], |
1cdade2c BF |
3345 | which might output something like: |
3346 | ||
3347 | ------------------------------------------------ | |
3348 | $ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 | |
3349 | 100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore | |
3350 | 100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap | |
3351 | 100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING | |
3352 | ... | |
3353 | 100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile | |
3354 | ... | |
3355 | ------------------------------------------------ | |
3356 | ||
3357 | So now you know that the missing blob was the data for a file named | |
1249d8ad TK |
3358 | `myfile`. And chances are you can also identify the directory--let's |
3359 | say it's in `somedirectory`. If you're lucky the missing copy might be | |
1cdade2c | 3360 | the same as the copy you have checked out in your working tree at |
1249d8ad | 3361 | `somedirectory/myfile`; you can test whether that's right with |
5162e697 | 3362 | linkgit:git-hash-object[1]: |
1cdade2c BF |
3363 | |
3364 | ------------------------------------------------ | |
3365 | $ git hash-object -w somedirectory/myfile | |
3366 | ------------------------------------------------ | |
3367 | ||
3368 | which will create and store a blob object with the contents of | |
a6e5ef7d | 3369 | somedirectory/myfile, and output the SHA-1 of that object. if you're |
1cdade2c BF |
3370 | extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in |
3371 | which case you've guessed right, and the corruption is fixed! | |
3372 | ||
3373 | Otherwise, you need more information. How do you tell which version of | |
3374 | the file has been lost? | |
3375 | ||
3376 | The easiest way to do this is with: | |
3377 | ||
3378 | ------------------------------------------------ | |
3379 | $ git log --raw --all --full-history -- somedirectory/myfile | |
3380 | ------------------------------------------------ | |
3381 | ||
3382 | Because you're asking for raw output, you'll now get something like | |
3383 | ||
3384 | ------------------------------------------------ | |
3385 | commit abc | |
3386 | Author: | |
3387 | Date: | |
3388 | ... | |
3389 | :100644 100644 4b9458b... newsha... M somedirectory/myfile | |
3390 | ||
3391 | ||
3392 | commit xyz | |
3393 | Author: | |
3394 | Date: | |
3395 | ||
3396 | ... | |
3397 | :100644 100644 oldsha... 4b9458b... M somedirectory/myfile | |
3398 | ------------------------------------------------ | |
3399 | ||
edfbbf7e ŠN |
3400 | This tells you that the immediately following version of the file was |
3401 | "newsha", and that the immediately preceding version was "oldsha". | |
1cdade2c BF |
3402 | You also know the commit messages that went with the change from oldsha |
3403 | to 4b9458b and with the change from 4b9458b to newsha. | |
3404 | ||
3405 | If you've been committing small enough changes, you may now have a good | |
3406 | shot at reconstructing the contents of the in-between state 4b9458b. | |
3407 | ||
3408 | If you can do that, you can now recreate the missing object with | |
3409 | ||
3410 | ------------------------------------------------ | |
3411 | $ git hash-object -w <recreated-file> | |
3412 | ------------------------------------------------ | |
3413 | ||
3414 | and your repository is good again! | |
3415 | ||
1249d8ad | 3416 | (Btw, you could have ignored the `fsck`, and started with doing a |
1cdade2c BF |
3417 | |
3418 | ------------------------------------------------ | |
3419 | $ git log --raw --all | |
3420 | ------------------------------------------------ | |
3421 | ||
1ab58e8d | 3422 | and just looked for the sha of the missing object (4b9458b..) in that |
da2c7b3d | 3423 | whole thing. It's up to you--Git does *have* a lot of information, it is |
1cdade2c BF |
3424 | just missing one particular blob version. |
3425 | ||
e34caace | 3426 | [[the-index]] |
1c097891 BF |
3427 | The index |
3428 | ----------- | |
3429 | ||
1249d8ad | 3430 | The index is a binary file (generally kept in `.git/index`) containing a |
a6e5ef7d | 3431 | sorted list of path names, each with permissions and the SHA-1 of a blob |
5162e697 | 3432 | object; linkgit:git-ls-files[1] can show you the contents of the index: |
b181d57f | 3433 | |
1c097891 BF |
3434 | ------------------------------------------------- |
3435 | $ git ls-files --stage | |
3436 | 100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore | |
3437 | 100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap | |
3438 | 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING | |
3439 | 100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore | |
3440 | 100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile | |
3441 | ... | |
3442 | 100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h | |
3443 | 100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c | |
3444 | 100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h | |
3445 | ------------------------------------------------- | |
3446 | ||
3447 | Note that in older documentation you may see the index called the | |
3448 | "current directory cache" or just the "cache". It has three important | |
3449 | properties: | |
3450 | ||
3451 | 1. The index contains all the information necessary to generate a single | |
3452 | (uniquely determined) tree object. | |
3453 | + | |
5162e697 | 3454 | For example, running linkgit:git-commit[1] generates this tree object |
1c097891 BF |
3455 | from the index, stores it in the object database, and uses it as the |
3456 | tree object associated with the new commit. | |
3457 | ||
3458 | 2. The index enables fast comparisons between the tree object it defines | |
3459 | and the working tree. | |
3460 | + | |
3461 | It does this by storing some additional data for each entry (such as | |
3462 | the last modified time). This data is not displayed above, and is not | |
3463 | stored in the created tree object, but it can be used to determine | |
3464 | quickly which files in the working directory differ from what was | |
2de9b711 | 3465 | stored in the index, and thus save Git from having to read all of the |
1c097891 BF |
3466 | data from such files to look for changes. |
3467 | ||
3468 | 3. It can efficiently represent information about merge conflicts | |
3469 | between different tree objects, allowing each pathname to be | |
b181d57f | 3470 | associated with sufficient information about the trees involved that |
1c097891 BF |
3471 | you can create a three-way merge between them. |
3472 | + | |
3473 | We saw in <<conflict-resolution>> that during a merge the index can | |
3474 | store multiple versions of a single file (called "stages"). The third | |
5162e697 | 3475 | column in the linkgit:git-ls-files[1] output above is the stage |
1c097891 BF |
3476 | number, and will take on values other than 0 for files with merge |
3477 | conflicts. | |
3478 | ||
3479 | The index is thus a sort of temporary staging area, which is filled with | |
3480 | a tree which you are in the process of working on. | |
3481 | ||
3482 | If you blow the index away entirely, you generally haven't lost any | |
3483 | information as long as you have the name of the tree that it described. | |
b181d57f | 3484 | |
38a457ba MV |
3485 | [[submodules]] |
3486 | Submodules | |
3487 | ========== | |
3488 | ||
6dd14366 MS |
3489 | Large projects are often composed of smaller, self-contained modules. For |
3490 | example, an embedded Linux distribution's source tree would include every | |
3491 | piece of software in the distribution with some local modifications; a movie | |
3492 | player might need to build against a specific, known-working version of a | |
3493 | decompression library; several independent programs might all share the same | |
3494 | build scripts. | |
3495 | ||
3496 | With centralized revision control systems this is often accomplished by | |
3497 | including every module in one single repository. Developers can check out | |
3498 | all modules or only the modules they need to work with. They can even modify | |
3499 | files across several modules in a single commit while moving things around | |
3500 | or updating APIs and translations. | |
3501 | ||
3502 | Git does not allow partial checkouts, so duplicating this approach in Git | |
3503 | would force developers to keep a local copy of modules they are not | |
3504 | interested in touching. Commits in an enormous checkout would be slower | |
3505 | than you'd expect as Git would have to scan every directory for changes. | |
3506 | If modules have a lot of local history, clones would take forever. | |
3507 | ||
3508 | On the plus side, distributed revision control systems can much better | |
3509 | integrate with external sources. In a centralized model, a single arbitrary | |
3510 | snapshot of the external project is exported from its own revision control | |
3511 | and then imported into the local revision control on a vendor branch. All | |
3512 | the history is hidden. With distributed revision control you can clone the | |
3513 | entire external history and much more easily follow development and re-merge | |
3514 | local changes. | |
3515 | ||
3516 | Git's submodule support allows a repository to contain, as a subdirectory, a | |
3517 | checkout of an external project. Submodules maintain their own identity; | |
3518 | the submodule support just stores the submodule repository location and | |
3519 | commit ID, so other developers who clone the containing project | |
3520 | ("superproject") can easily clone all the submodules at the same revision. | |
3521 | Partial checkouts of the superproject are possible: you can tell Git to | |
3522 | clone none, some or all of the submodules. | |
3523 | ||
5162e697 | 3524 | The linkgit:git-submodule[1] command is available since Git 1.5.3. Users |
6dd14366 MS |
3525 | with Git 1.5.2 can look up the submodule commits in the repository and |
3526 | manually check them out; earlier versions won't recognize the submodules at | |
3527 | all. | |
38a457ba | 3528 | |
ddd4ddef | 3529 | To see how submodule support works, create four example |
38a457ba MV |
3530 | repositories that can be used later as a submodule: |
3531 | ||
3532 | ------------------------------------------------- | |
3533 | $ mkdir ~/git | |
3534 | $ cd ~/git | |
3535 | $ for i in a b c d | |
3536 | do | |
3537 | mkdir $i | |
3538 | cd $i | |
3539 | git init | |
3540 | echo "module $i" > $i.txt | |
3541 | git add $i.txt | |
3542 | git commit -m "Initial commit, submodule $i" | |
3543 | cd .. | |
3544 | done | |
3545 | ------------------------------------------------- | |
3546 | ||
3547 | Now create the superproject and add all the submodules: | |
3548 | ||
3549 | ------------------------------------------------- | |
3550 | $ mkdir super | |
3551 | $ cd super | |
3552 | $ git init | |
3553 | $ for i in a b c d | |
3554 | do | |
a56bf585 | 3555 | git submodule add ~/git/$i $i |
38a457ba MV |
3556 | done |
3557 | ------------------------------------------------- | |
3558 | ||
3559 | NOTE: Do not use local URLs here if you plan to publish your superproject! | |
3560 | ||
6127c086 | 3561 | See what files `git submodule` created: |
38a457ba MV |
3562 | |
3563 | ------------------------------------------------- | |
3564 | $ ls -a | |
3565 | . .. .git .gitmodules a b c d | |
3566 | ------------------------------------------------- | |
3567 | ||
6127c086 | 3568 | The `git submodule add <repo> <path>` command does a couple of things: |
38a457ba | 3569 | |
1249d8ad | 3570 | - It clones the submodule from `<repo>` to the given `<path>` under the |
a56bf585 | 3571 | current directory and by default checks out the master branch. |
5162e697 | 3572 | - It adds the submodule's clone path to the linkgit:gitmodules[5] file and |
6dd14366 | 3573 | adds this file to the index, ready to be committed. |
38a457ba MV |
3574 | - It adds the submodule's current commit ID to the index, ready to be |
3575 | committed. | |
3576 | ||
3577 | Commit the superproject: | |
3578 | ||
3579 | ------------------------------------------------- | |
3580 | $ git commit -m "Add submodules a, b, c and d." | |
3581 | ------------------------------------------------- | |
3582 | ||
3583 | Now clone the superproject: | |
3584 | ||
3585 | ------------------------------------------------- | |
3586 | $ cd .. | |
3587 | $ git clone super cloned | |
3588 | $ cd cloned | |
3589 | ------------------------------------------------- | |
3590 | ||
3591 | The submodule directories are there, but they're empty: | |
3592 | ||
3593 | ------------------------------------------------- | |
3594 | $ ls -a a | |
3595 | . .. | |
3596 | $ git submodule status | |
3597 | -d266b9873ad50488163457f025db7cdd9683d88b a | |
3598 | -e81d457da15309b4fef4249aba9b50187999670d b | |
3599 | -c1536a972b9affea0f16e0680ba87332dc059146 c | |
3600 | -d96249ff5d57de5de093e6baff9e0aafa5276a74 d | |
3601 | ------------------------------------------------- | |
3602 | ||
3603 | NOTE: The commit object names shown above would be different for you, but they | |
3604 | should match the HEAD commit object names of your repositories. You can check | |
3605 | it by running `git ls-remote ../a`. | |
3606 | ||
3607 | Pulling down the submodules is a two-step process. First run `git submodule | |
3608 | init` to add the submodule repository URLs to `.git/config`: | |
3609 | ||
3610 | ------------------------------------------------- | |
3611 | $ git submodule init | |
3612 | ------------------------------------------------- | |
3613 | ||
6127c086 | 3614 | Now use `git submodule update` to clone the repositories and check out the |
38a457ba MV |
3615 | commits specified in the superproject: |
3616 | ||
3617 | ------------------------------------------------- | |
3618 | $ git submodule update | |
3619 | $ cd a | |
3620 | $ ls -a | |
3621 | . .. .git a.txt | |
3622 | ------------------------------------------------- | |
3623 | ||
6127c086 FC |
3624 | One major difference between `git submodule update` and `git submodule add` is |
3625 | that `git submodule update` checks out a specific commit, rather than the tip | |
38a457ba MV |
3626 | of a branch. It's like checking out a tag: the head is detached, so you're not |
3627 | working on a branch. | |
3628 | ||
3629 | ------------------------------------------------- | |
3630 | $ git branch | |
95f9be55 | 3631 | * (detached from d266b98) |
38a457ba MV |
3632 | master |
3633 | ------------------------------------------------- | |
3634 | ||
3635 | If you want to make a change within a submodule and you have a detached head, | |
3636 | then you should create or checkout a branch, make your changes, publish the | |
3637 | change within the submodule, and then update the superproject to reference the | |
3638 | new commit: | |
3639 | ||
3640 | ------------------------------------------------- | |
3641 | $ git checkout master | |
3642 | ------------------------------------------------- | |
3643 | ||
3644 | or | |
3645 | ||
3646 | ------------------------------------------------- | |
3647 | $ git checkout -b fix-up | |
3648 | ------------------------------------------------- | |
3649 | ||
3650 | then | |
3651 | ||
3652 | ------------------------------------------------- | |
3653 | $ echo "adding a line again" >> a.txt | |
3654 | $ git commit -a -m "Updated the submodule from within the superproject." | |
3655 | $ git push | |
3656 | $ cd .. | |
3657 | $ git diff | |
3658 | diff --git a/a b/a | |
3659 | index d266b98..261dfac 160000 | |
3660 | --- a/a | |
3661 | +++ b/a | |
3662 | @@ -1 +1 @@ | |
3663 | -Subproject commit d266b9873ad50488163457f025db7cdd9683d88b | |
3664 | +Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24 | |
3665 | $ git add a | |
3666 | $ git commit -m "Updated submodule a." | |
3667 | $ git push | |
3668 | ------------------------------------------------- | |
3669 | ||
3670 | You have to run `git submodule update` after `git pull` if you want to update | |
3671 | submodules, too. | |
3672 | ||
3673 | Pitfalls with submodules | |
3674 | ------------------------ | |
3675 | ||
3676 | Always publish the submodule change before publishing the change to the | |
3677 | superproject that references it. If you forget to publish the submodule change, | |
3678 | others won't be able to clone the repository: | |
3679 | ||
3680 | ------------------------------------------------- | |
3681 | $ cd ~/git/super/a | |
3682 | $ echo i added another line to this file >> a.txt | |
3683 | $ git commit -a -m "doing it wrong this time" | |
3684 | $ cd .. | |
3685 | $ git add a | |
3686 | $ git commit -m "Updated submodule a again." | |
3687 | $ git push | |
3688 | $ cd ~/git/cloned | |
3689 | $ git pull | |
3690 | $ git submodule update | |
3691 | error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git. | |
3692 | Did you forget to 'git add'? | |
3693 | Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a' | |
3694 | ------------------------------------------------- | |
3695 | ||
2de9b711 | 3696 | In older Git versions it could be easily forgotten to commit new or modified |
8d9e7d52 | 3697 | files in a submodule, which silently leads to similar problems as not pushing |
1249d8ad | 3698 | the submodule changes. Starting with Git 1.7.0 both `git status` and `git diff` |
8d9e7d52 | 3699 | in the superproject show submodules as modified when they contain new or |
1249d8ad TK |
3700 | modified files to protect against accidentally committing such a state. `git |
3701 | diff` will also add a `-dirty` to the work tree side when generating patch | |
3702 | output or used with the `--submodule` option: | |
8d9e7d52 JL |
3703 | |
3704 | ------------------------------------------------- | |
3705 | $ git diff | |
3706 | diff --git a/sub b/sub | |
3707 | --- a/sub | |
3708 | +++ b/sub | |
3709 | @@ -1 +1 @@ | |
3710 | -Subproject commit 3f356705649b5d566d97ff843cf193359229a453 | |
3711 | +Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty | |
3712 | $ git diff --submodule | |
3713 | Submodule sub 3f35670..3f35670-dirty: | |
3714 | ------------------------------------------------- | |
3715 | ||
38a457ba MV |
3716 | You also should not rewind branches in a submodule beyond commits that were |
3717 | ever recorded in any superproject. | |
3718 | ||
3719 | It's not safe to run `git submodule update` if you've made and committed | |
3720 | changes within a submodule without checking out a branch first. They will be | |
3721 | silently overwritten: | |
3722 | ||
3723 | ------------------------------------------------- | |
3724 | $ cat a.txt | |
3725 | module a | |
3726 | $ echo line added from private2 >> a.txt | |
3727 | $ git commit -a -m "line added inside private2" | |
3728 | $ cd .. | |
3729 | $ git submodule update | |
3730 | Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b' | |
3731 | $ cd a | |
3732 | $ cat a.txt | |
3733 | module a | |
3734 | ------------------------------------------------- | |
3735 | ||
3736 | NOTE: The changes are still visible in the submodule's reflog. | |
3737 | ||
91486733 TK |
3738 | If you have uncommitted changes in your submodule working tree, `git |
3739 | submodule update` will not overwrite them. Instead, you get the usual | |
3740 | warning about not being able switch from a dirty branch. | |
38a457ba | 3741 | |
1c6045ff | 3742 | [[low-level-operations]] |
2de9b711 | 3743 | Low-level Git operations |
1c6045ff | 3744 | ======================== |
b181d57f | 3745 | |
1c6045ff | 3746 | Many of the higher-level commands were originally implemented as shell |
2de9b711 TA |
3747 | scripts using a smaller core of low-level Git commands. These can still |
3748 | be useful when doing unusual things with Git, or just as a way to | |
1c6045ff | 3749 | understand its inner workings. |
b181d57f | 3750 | |
1bbf1c79 BF |
3751 | [[object-manipulation]] |
3752 | Object access and manipulation | |
3753 | ------------------------------ | |
3754 | ||
5162e697 DM |
3755 | The linkgit:git-cat-file[1] command can show the contents of any object, |
3756 | though the higher-level linkgit:git-show[1] is usually more useful. | |
1bbf1c79 | 3757 | |
5162e697 | 3758 | The linkgit:git-commit-tree[1] command allows constructing commits with |
1bbf1c79 BF |
3759 | arbitrary parents and trees. |
3760 | ||
5162e697 DM |
3761 | A tree can be created with linkgit:git-write-tree[1] and its data can be |
3762 | accessed by linkgit:git-ls-tree[1]. Two trees can be compared with | |
3763 | linkgit:git-diff-tree[1]. | |
1bbf1c79 | 3764 | |
5162e697 DM |
3765 | A tag is created with linkgit:git-mktag[1], and the signature can be |
3766 | verified by linkgit:git-verify-tag[1], though it is normally simpler to | |
3767 | use linkgit:git-tag[1] for both. | |
1bbf1c79 | 3768 | |
e34caace | 3769 | [[the-workflow]] |
b181d57f BF |
3770 | The Workflow |
3771 | ------------ | |
3772 | ||
5162e697 DM |
3773 | High-level operations such as linkgit:git-commit[1], |
3774 | linkgit:git-checkout[1] and linkgit:git-reset[1] work by moving data | |
06ada152 RW |
3775 | between the working tree, the index, and the object database. Git |
3776 | provides low-level operations which perform each of these steps | |
3777 | individually. | |
1c6045ff | 3778 | |
2de9b711 | 3779 | Generally, all Git operations work on the index file. Some operations |
b181d57f | 3780 | work *purely* on the index file (showing the current state of the |
1c6045ff BF |
3781 | index), but most operations move data between the index file and either |
3782 | the database or the working directory. Thus there are four main | |
3783 | combinations: | |
b181d57f | 3784 | |
e34caace | 3785 | [[working-directory-to-index]] |
b181d57f BF |
3786 | working directory -> index |
3787 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3788 | ||
5162e697 | 3789 | The linkgit:git-update-index[1] command updates the index with |
1c6045ff BF |
3790 | information from the working directory. You generally update the |
3791 | index information by just specifying the filename you want to update, | |
3792 | like so: | |
b181d57f BF |
3793 | |
3794 | ------------------------------------------------- | |
1c6045ff | 3795 | $ git update-index filename |
b181d57f BF |
3796 | ------------------------------------------------- |
3797 | ||
5fe8f49b | 3798 | but to avoid common mistakes with filename globbing etc., the command |
b181d57f BF |
3799 | will not normally add totally new entries or remove old entries, |
3800 | i.e. it will normally just update existing cache entries. | |
3801 | ||
2de9b711 | 3802 | To tell Git that yes, you really do realize that certain files no |
b181d57f BF |
3803 | longer exist, or that new files should be added, you |
3804 | should use the `--remove` and `--add` flags respectively. | |
3805 | ||
3806 | NOTE! A `--remove` flag does 'not' mean that subsequent filenames will | |
3807 | necessarily be removed: if the files still exist in your directory | |
3808 | structure, the index will be updated with their new status, not | |
10455d2a | 3809 | removed. The only thing `--remove` means is that update-index will be |
b181d57f BF |
3810 | considering a removed file to be a valid thing, and if the file really |
3811 | does not exist any more, it will update the index accordingly. | |
3812 | ||
467c0197 | 3813 | As a special case, you can also do `git update-index --refresh`, which |
b181d57f BF |
3814 | will refresh the "stat" information of each index to match the current |
3815 | stat information. It will 'not' update the object status itself, and | |
3816 | it will only update the fields that are used to quickly test whether | |
3817 | an object still matches its old backing store object. | |
3818 | ||
5162e697 DM |
3819 | The previously introduced linkgit:git-add[1] is just a wrapper for |
3820 | linkgit:git-update-index[1]. | |
1c6045ff | 3821 | |
e34caace | 3822 | [[index-to-object-database]] |
b181d57f BF |
3823 | index -> object database |
3824 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
3825 | ||
3826 | You write your current index file to a "tree" object with the program | |
3827 | ||
3828 | ------------------------------------------------- | |
1c6045ff | 3829 | $ git write-tree |
b181d57f BF |
3830 | ------------------------------------------------- |
3831 | ||
2ef8ac1b | 3832 | that doesn't come with any options--it will just write out the |
b181d57f BF |
3833 | current index into the set of tree objects that describe that state, |
3834 | and it will return the name of the resulting top-level tree. You can | |
3835 | use that tree to re-generate the index at any time by going in the | |
3836 | other direction: | |
3837 | ||
e34caace | 3838 | [[object-database-to-index]] |
b181d57f BF |
3839 | object database -> index |
3840 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
3841 | ||
3842 | You read a "tree" file from the object database, and use that to | |
2ef8ac1b | 3843 | populate (and overwrite--don't do this if your index contains any |
b181d57f BF |
3844 | unsaved state that you might want to restore later!) your current |
3845 | index. Normal operation is just | |
3846 | ||
3847 | ------------------------------------------------- | |
a6e5ef7d | 3848 | $ git read-tree <SHA-1 of tree> |
b181d57f BF |
3849 | ------------------------------------------------- |
3850 | ||
3851 | and your index file will now be equivalent to the tree that you saved | |
3852 | earlier. However, that is only your 'index' file: your working | |
3853 | directory contents have not been modified. | |
3854 | ||
e34caace | 3855 | [[index-to-working-directory]] |
b181d57f BF |
3856 | index -> working directory |
3857 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3858 | ||
3859 | You update your working directory from the index by "checking out" | |
3860 | files. This is not a very common operation, since normally you'd just | |
3861 | keep your files updated, and rather than write to your working | |
3862 | directory, you'd tell the index files about the changes in your | |
6127c086 | 3863 | working directory (i.e. `git update-index`). |
b181d57f BF |
3864 | |
3865 | However, if you decide to jump to a new version, or check out somebody | |
3866 | else's version, or just restore a previous tree, you'd populate your | |
3867 | index file with read-tree, and then you need to check out the result | |
3868 | with | |
3869 | ||
3870 | ------------------------------------------------- | |
b1889c36 | 3871 | $ git checkout-index filename |
b181d57f BF |
3872 | ------------------------------------------------- |
3873 | ||
3874 | or, if you want to check out all of the index, use `-a`. | |
3875 | ||
6127c086 | 3876 | NOTE! `git checkout-index` normally refuses to overwrite old files, so |
b181d57f | 3877 | if you have an old version of the tree already checked out, you will |
1249d8ad | 3878 | need to use the `-f` flag ('before' the `-a` flag or the filename) to |
b181d57f BF |
3879 | 'force' the checkout. |
3880 | ||
3881 | ||
3882 | Finally, there are a few odds and ends which are not purely moving | |
3883 | from one representation to the other: | |
3884 | ||
e34caace | 3885 | [[tying-it-all-together]] |
b181d57f BF |
3886 | Tying it all together |
3887 | ~~~~~~~~~~~~~~~~~~~~~ | |
3888 | ||
1249d8ad | 3889 | To commit a tree you have instantiated with `git write-tree`, you'd |
b181d57f | 3890 | create a "commit" object that refers to that tree and the history |
2ef8ac1b | 3891 | behind it--most notably the "parent" commits that preceded it in |
b181d57f BF |
3892 | history. |
3893 | ||
3894 | Normally a "commit" has one parent: the previous state of the tree | |
3895 | before a certain change was made. However, sometimes it can have two | |
3896 | or more parent commits, in which case we call it a "merge", due to the | |
3897 | fact that such a commit brings together ("merges") two or more | |
3898 | previous states represented by other commits. | |
3899 | ||
3900 | In other words, while a "tree" represents a particular directory state | |
ddd4ddef | 3901 | of a working directory, a "commit" represents that state in time, |
b181d57f BF |
3902 | and explains how we got there. |
3903 | ||
3904 | You create a commit object by giving it the tree that describes the | |
3905 | state at the time of the commit, and a list of parents: | |
3906 | ||
3907 | ------------------------------------------------- | |
0adda936 | 3908 | $ git commit-tree <tree> -p <parent> [(-p <parent2>)...] |
b181d57f BF |
3909 | ------------------------------------------------- |
3910 | ||
3911 | and then giving the reason for the commit on stdin (either through | |
3912 | redirection from a pipe or file, or by just typing it at the tty). | |
3913 | ||
6127c086 | 3914 | `git commit-tree` will return the name of the object that represents |
b181d57f | 3915 | that commit, and you should save it away for later use. Normally, |
2de9b711 | 3916 | you'd commit a new `HEAD` state, and while Git doesn't care where you |
b181d57f BF |
3917 | save the note about that state, in practice we tend to just write the |
3918 | result to the file pointed at by `.git/HEAD`, so that we can always see | |
3919 | what the last committed state was. | |
3920 | ||
381183fb | 3921 | Here is a picture that illustrates how various pieces fit together: |
b181d57f BF |
3922 | |
3923 | ------------ | |
3924 | ||
3925 | commit-tree | |
3926 | commit obj | |
3927 | +----+ | |
3928 | | | | |
3929 | | | | |
3930 | V V | |
3931 | +-----------+ | |
3932 | | Object DB | | |
3933 | | Backing | | |
3934 | | Store | | |
3935 | +-----------+ | |
3936 | ^ | |
3937 | write-tree | | | |
3938 | tree obj | | | |
3939 | | | read-tree | |
3940 | | | tree obj | |
3941 | V | |
3942 | +-----------+ | |
3943 | | Index | | |
3944 | | "cache" | | |
3945 | +-----------+ | |
3946 | update-index ^ | |
3947 | blob obj | | | |
3948 | | | | |
3949 | checkout-index -u | | checkout-index | |
3950 | stat | | blob obj | |
3951 | V | |
3952 | +-----------+ | |
3953 | | Working | | |
3954 | | Directory | | |
3955 | +-----------+ | |
3956 | ||
3957 | ------------ | |
3958 | ||
3959 | ||
e34caace | 3960 | [[examining-the-data]] |
b181d57f BF |
3961 | Examining the data |
3962 | ------------------ | |
3963 | ||
3964 | You can examine the data represented in the object database and the | |
3965 | index with various helper tools. For every object, you can use | |
5162e697 | 3966 | linkgit:git-cat-file[1] to examine details about the |
b181d57f BF |
3967 | object: |
3968 | ||
3969 | ------------------------------------------------- | |
b1889c36 | 3970 | $ git cat-file -t <objectname> |
b181d57f BF |
3971 | ------------------------------------------------- |
3972 | ||
3973 | shows the type of the object, and once you have the type (which is | |
3974 | usually implicit in where you find the object), you can use | |
3975 | ||
3976 | ------------------------------------------------- | |
b1889c36 | 3977 | $ git cat-file blob|tree|commit|tag <objectname> |
b181d57f BF |
3978 | ------------------------------------------------- |
3979 | ||
3980 | to show its contents. NOTE! Trees have binary content, and as a result | |
3981 | there is a special helper for showing that content, called | |
6127c086 | 3982 | `git ls-tree`, which turns the binary content into a more easily |
b181d57f BF |
3983 | readable form. |
3984 | ||
3985 | It's especially instructive to look at "commit" objects, since those | |
3986 | tend to be small and fairly self-explanatory. In particular, if you | |
3987 | follow the convention of having the top commit name in `.git/HEAD`, | |
3988 | you can do | |
3989 | ||
3990 | ------------------------------------------------- | |
b1889c36 | 3991 | $ git cat-file commit HEAD |
b181d57f BF |
3992 | ------------------------------------------------- |
3993 | ||
3994 | to see what the top commit was. | |
3995 | ||
e34caace | 3996 | [[merging-multiple-trees]] |
b181d57f | 3997 | Merging multiple trees |
d19fbc3c BF |
3998 | ---------------------- |
3999 | ||
e8e9964d TA |
4000 | Git can help you perform a three-way merge, which can in turn be |
4001 | used for a many-way merge by repeating the merge procedure several | |
4002 | times. The usual situation is that you only do one three-way merge | |
4003 | (reconciling two lines of history) and commit the result, but if | |
4004 | you like to, you can merge several branches in one go. | |
b181d57f | 4005 | |
e8e9964d TA |
4006 | To perform a three-way merge, you start with the two commits you |
4007 | want to merge, find their closest common parent (a third commit), | |
4008 | and compare the trees corresponding to these three commits. | |
b181d57f | 4009 | |
e8e9964d TA |
4010 | To get the "base" for the merge, look up the common parent of two |
4011 | commits: | |
b181d57f BF |
4012 | |
4013 | ------------------------------------------------- | |
b1889c36 | 4014 | $ git merge-base <commit1> <commit2> |
b181d57f BF |
4015 | ------------------------------------------------- |
4016 | ||
e8e9964d TA |
4017 | This prints the name of a commit they are both based on. You should |
4018 | now look up the tree objects of those commits, which you can easily | |
4019 | do with | |
b181d57f BF |
4020 | |
4021 | ------------------------------------------------- | |
b1889c36 | 4022 | $ git cat-file commit <commitname> | head -1 |
b181d57f BF |
4023 | ------------------------------------------------- |
4024 | ||
4025 | since the tree object information is always the first line in a commit | |
4026 | object. | |
4027 | ||
1191ee18 | 4028 | Once you know the three trees you are going to merge (the one "original" |
c64415e2 | 4029 | tree, aka the common tree, and the two "result" trees, aka the branches |
1191ee18 BF |
4030 | you want to merge), you do a "merge" read into the index. This will |
4031 | complain if it has to throw away your old index contents, so you should | |
2ef8ac1b | 4032 | make sure that you've committed those--in fact you would normally |
1191ee18 BF |
4033 | always do a merge against your last commit (which should thus match what |
4034 | you have in your current index anyway). | |
b181d57f BF |
4035 | |
4036 | To do the merge, do | |
4037 | ||
4038 | ------------------------------------------------- | |
b1889c36 | 4039 | $ git read-tree -m -u <origtree> <yourtree> <targettree> |
b181d57f BF |
4040 | ------------------------------------------------- |
4041 | ||
4042 | which will do all trivial merge operations for you directly in the | |
4043 | index file, and you can just write the result out with | |
467c0197 | 4044 | `git write-tree`. |
b181d57f BF |
4045 | |
4046 | ||
e34caace | 4047 | [[merging-multiple-trees-2]] |
b181d57f BF |
4048 | Merging multiple trees, continued |
4049 | --------------------------------- | |
4050 | ||
4051 | Sadly, many merges aren't trivial. If there are files that have | |
06ada152 | 4052 | been added, moved or removed, or if both branches have modified the |
b181d57f BF |
4053 | same file, you will be left with an index tree that contains "merge |
4054 | entries" in it. Such an index tree can 'NOT' be written out to a tree | |
4055 | object, and you will have to resolve any such merge clashes using | |
4056 | other tools before you can write out the result. | |
4057 | ||
b1889c36 | 4058 | You can examine such index state with `git ls-files --unmerged` |
b181d57f BF |
4059 | command. An example: |
4060 | ||
4061 | ------------------------------------------------ | |
b1889c36 JN |
4062 | $ git read-tree -m $orig HEAD $target |
4063 | $ git ls-files --unmerged | |
b181d57f BF |
4064 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c |
4065 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c | |
4066 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c | |
4067 | ------------------------------------------------ | |
4068 | ||
b1889c36 | 4069 | Each line of the `git ls-files --unmerged` output begins with |
a6e5ef7d | 4070 | the blob mode bits, blob SHA-1, 'stage number', and the |
2de9b711 | 4071 | filename. The 'stage number' is Git's way to say which tree it |
edfbbf7e ŠN |
4072 | came from: stage 1 corresponds to the `$orig` tree, stage 2 to |
4073 | the `HEAD` tree, and stage 3 to the `$target` tree. | |
b181d57f BF |
4074 | |
4075 | Earlier we said that trivial merges are done inside | |
6127c086 | 4076 | `git read-tree -m`. For example, if the file did not change |
a58088ab | 4077 | from `$orig` to `HEAD` or `$target`, or if the file changed |
b181d57f BF |
4078 | from `$orig` to `HEAD` and `$orig` to `$target` the same way, |
4079 | obviously the final outcome is what is in `HEAD`. What the | |
4080 | above example shows is that file `hello.c` was changed from | |
4081 | `$orig` to `HEAD` and `$orig` to `$target` in a different way. | |
4082 | You could resolve this by running your favorite 3-way merge | |
2de9b711 | 4083 | program, e.g. `diff3`, `merge`, or Git's own merge-file, on |
c64415e2 | 4084 | the blob objects from these three stages yourself, like this: |
b181d57f BF |
4085 | |
4086 | ------------------------------------------------ | |
b1889c36 JN |
4087 | $ git cat-file blob 263414f... >hello.c~1 |
4088 | $ git cat-file blob 06fa6a2... >hello.c~2 | |
4089 | $ git cat-file blob cc44c73... >hello.c~3 | |
c64415e2 | 4090 | $ git merge-file hello.c~2 hello.c~1 hello.c~3 |
b181d57f BF |
4091 | ------------------------------------------------ |
4092 | ||
4093 | This would leave the merge result in `hello.c~2` file, along | |
4094 | with conflict markers if there are conflicts. After verifying | |
2de9b711 | 4095 | the merge result makes sense, you can tell Git what the final |
b181d57f BF |
4096 | merge result for this file is by: |
4097 | ||
4098 | ------------------------------------------------- | |
4099 | $ mv -f hello.c~2 hello.c | |
b1889c36 | 4100 | $ git update-index hello.c |
b181d57f BF |
4101 | ------------------------------------------------- |
4102 | ||
6127c086 | 4103 | When a path is in the "unmerged" state, running `git update-index` for |
2de9b711 | 4104 | that path tells Git to mark the path resolved. |
b181d57f | 4105 | |
2de9b711 | 4106 | The above is the description of a Git merge at the lowest level, |
b181d57f | 4107 | to help you understand what conceptually happens under the hood. |
2de9b711 | 4108 | In practice, nobody, not even Git itself, runs `git cat-file` three times |
6127c086 | 4109 | for this. There is a `git merge-index` program that extracts the |
b181d57f BF |
4110 | stages to temporary files and calls a "merge" script on it: |
4111 | ||
4112 | ------------------------------------------------- | |
b1889c36 | 4113 | $ git merge-index git-merge-one-file hello.c |
b181d57f BF |
4114 | ------------------------------------------------- |
4115 | ||
6127c086 | 4116 | and that is what higher level `git merge -s resolve` is implemented with. |
b181d57f | 4117 | |
971aa71f | 4118 | [[hacking-git]] |
2de9b711 | 4119 | Hacking Git |
971aa71f BF |
4120 | =========== |
4121 | ||
2de9b711 TA |
4122 | This chapter covers internal details of the Git implementation which |
4123 | probably only Git developers need to understand. | |
971aa71f | 4124 | |
f2327c6c BF |
4125 | [[object-details]] |
4126 | Object storage format | |
4127 | --------------------- | |
4128 | ||
4129 | All objects have a statically determined "type" which identifies the | |
4130 | format of the object (i.e. how it is used, and how it can refer to other | |
4131 | objects). There are currently four different object types: "blob", | |
4132 | "tree", "commit", and "tag". | |
4133 | ||
4134 | Regardless of object type, all objects share the following | |
4135 | characteristics: they are all deflated with zlib, and have a header | |
4136 | that not only specifies their type, but also provides size information | |
a6e5ef7d | 4137 | about the data in the object. It's worth noting that the SHA-1 hash |
f2327c6c BF |
4138 | that is used to name the object is the hash of the original data |
4139 | plus this header, so `sha1sum` 'file' does not match the object name | |
4140 | for 'file'. | |
f2327c6c BF |
4141 | |
4142 | As a result, the general consistency of an object can always be tested | |
4143 | independently of the contents or the type of the object: all objects can | |
4144 | be validated by verifying that (a) their hashes match the content of the | |
4145 | file and (b) the object successfully inflates to a stream of bytes that | |
1249d8ad TK |
4146 | forms a sequence of |
4147 | `<ascii type without space> + <space> + <ascii decimal size> + | |
4148 | <byte\0> + <binary object data>`. | |
f2327c6c BF |
4149 | |
4150 | The structured objects can further have their structure and | |
4151 | connectivity to other objects verified. This is generally done with | |
6127c086 | 4152 | the `git fsck` program, which generates a full dependency graph |
f2327c6c BF |
4153 | of all objects, and verifies their internal consistency (in addition |
4154 | to just verifying their superficial consistency through the hash). | |
4155 | ||
126640af | 4156 | [[birdview-on-the-source-code]] |
a5fc33b4 BF |
4157 | A birds-eye view of Git's source code |
4158 | ------------------------------------- | |
126640af | 4159 | |
a5fc33b4 BF |
4160 | It is not always easy for new developers to find their way through Git's |
4161 | source code. This section gives you a little guidance to show where to | |
4162 | start. | |
126640af | 4163 | |
a5fc33b4 | 4164 | A good place to start is with the contents of the initial commit, with: |
126640af JS |
4165 | |
4166 | ---------------------------------------------------- | |
a5fc33b4 | 4167 | $ git checkout e83c5163 |
126640af JS |
4168 | ---------------------------------------------------- |
4169 | ||
2de9b711 | 4170 | The initial revision lays the foundation for almost everything Git has |
a5fc33b4 | 4171 | today, but is small enough to read in one sitting. |
126640af | 4172 | |
a5fc33b4 BF |
4173 | Note that terminology has changed since that revision. For example, the |
4174 | README in that revision uses the word "changeset" to describe what we | |
4175 | now call a <<def_commit_object,commit>>. | |
126640af | 4176 | |
843c81dc | 4177 | Also, we do not call it "cache" any more, but rather "index"; however, the |
126640af JS |
4178 | file is still called `cache.h`. Remark: Not much reason to change it now, |
4179 | especially since there is no good single name for it anyway, because it is | |
4180 | basically _the_ header file which is included by _all_ of Git's C sources. | |
4181 | ||
a5fc33b4 BF |
4182 | If you grasp the ideas in that initial commit, you should check out a |
4183 | more recent version and skim `cache.h`, `object.h` and `commit.h`. | |
126640af JS |
4184 | |
4185 | In the early days, Git (in the tradition of UNIX) was a bunch of programs | |
4186 | which were extremely simple, and which you used in scripts, piping the | |
4187 | output of one into another. This turned out to be good for initial | |
4188 | development, since it was easier to test new things. However, recently | |
4189 | many of these parts have become builtins, and some of the core has been | |
4190 | "libified", i.e. put into libgit.a for performance, portability reasons, | |
4191 | and to avoid code duplication. | |
4192 | ||
4193 | By now, you know what the index is (and find the corresponding data | |
4194 | structures in `cache.h`), and that there are just a couple of object types | |
4195 | (blobs, trees, commits and tags) which inherit their common structure from | |
4196 | `struct object`, which is their first member (and thus, you can cast e.g. | |
4197 | `(struct object *)commit` to achieve the _same_ as `&commit->object`, i.e. | |
4198 | get at the object name and flags). | |
4199 | ||
4200 | Now is a good point to take a break to let this information sink in. | |
4201 | ||
4202 | Next step: get familiar with the object naming. Read <<naming-commits>>. | |
4203 | There are quite a few ways to name an object (and not only revisions!). | |
4204 | All of these are handled in `sha1_name.c`. Just have a quick look at | |
4205 | the function `get_sha1()`. A lot of the special handling is done by | |
4206 | functions like `get_sha1_basic()` or the likes. | |
4207 | ||
4208 | This is just to get you into the groove for the most libified part of Git: | |
4209 | the revision walker. | |
4210 | ||
6127c086 | 4211 | Basically, the initial version of `git log` was a shell script: |
126640af JS |
4212 | |
4213 | ---------------------------------------------------------------- | |
4214 | $ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ | |
4215 | LESS=-S ${PAGER:-less} | |
4216 | ---------------------------------------------------------------- | |
4217 | ||
4218 | What does this mean? | |
4219 | ||
6127c086 | 4220 | `git rev-list` is the original version of the revision walker, which |
126640af | 4221 | _always_ printed a list of revisions to stdout. It is still functional, |
57f6ec02 | 4222 | and needs to, since most new Git commands start out as scripts using |
6127c086 | 4223 | `git rev-list`. |
126640af | 4224 | |
6127c086 | 4225 | `git rev-parse` is not as important any more; it was only used to filter out |
126640af JS |
4226 | options that were relevant for the different plumbing commands that were |
4227 | called by the script. | |
4228 | ||
6127c086 | 4229 | Most of what `git rev-list` did is contained in `revision.c` and |
126640af JS |
4230 | `revision.h`. It wraps the options in a struct named `rev_info`, which |
4231 | controls how and what revisions are walked, and more. | |
4232 | ||
6127c086 | 4233 | The original job of `git rev-parse` is now taken by the function |
126640af JS |
4234 | `setup_revisions()`, which parses the revisions and the common command line |
4235 | options for the revision walker. This information is stored in the struct | |
4236 | `rev_info` for later consumption. You can do your own command line option | |
4237 | parsing after calling `setup_revisions()`. After that, you have to call | |
4238 | `prepare_revision_walk()` for initialization, and then you can get the | |
4239 | commits one by one with the function `get_revision()`. | |
4240 | ||
4241 | If you are interested in more details of the revision walking process, | |
4242 | just have a look at the first implementation of `cmd_log()`; call | |
6cf378f0 | 4243 | `git show v1.3.0~155^2~4` and scroll down to that function (note that you |
126640af JS |
4244 | no longer need to call `setup_pager()` directly). |
4245 | ||
6127c086 | 4246 | Nowadays, `git log` is a builtin, which means that it is _contained_ in the |
126640af JS |
4247 | command `git`. The source side of a builtin is |
4248 | ||
09b7e220 PH |
4249 | - a function called `cmd_<bla>`, typically defined in `builtin/<bla.c>` |
4250 | (note that older versions of Git used to have it in `builtin-<bla>.c` | |
4251 | instead), and declared in `builtin.h`. | |
126640af JS |
4252 | |
4253 | - an entry in the `commands[]` array in `git.c`, and | |
4254 | ||
4255 | - an entry in `BUILTIN_OBJECTS` in the `Makefile`. | |
4256 | ||
4257 | Sometimes, more than one builtin is contained in one source file. For | |
09b7e220 | 4258 | example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin/log.c`, |
126640af JS |
4259 | since they share quite a bit of code. In that case, the commands which are |
4260 | _not_ named like the `.c` file in which they live have to be listed in | |
4261 | `BUILT_INS` in the `Makefile`. | |
4262 | ||
6127c086 | 4263 | `git log` looks more complicated in C than it does in the original script, |
126640af JS |
4264 | but that allows for a much greater flexibility and performance. |
4265 | ||
4266 | Here again it is a good point to take a pause. | |
4267 | ||
4268 | Lesson three is: study the code. Really, it is the best way to learn about | |
4269 | the organization of Git (after you know the basic concepts). | |
4270 | ||
4271 | So, think about something which you are interested in, say, "how can I | |
4272 | access a blob just knowing the object name of it?". The first step is to | |
4273 | find a Git command with which you can do it. In this example, it is either | |
6127c086 | 4274 | `git show` or `git cat-file`. |
126640af | 4275 | |
6127c086 | 4276 | For the sake of clarity, let's stay with `git cat-file`, because it |
126640af JS |
4277 | |
4278 | - is plumbing, and | |
4279 | ||
4280 | - was around even in the initial commit (it literally went only through | |
09b7e220 | 4281 | some 20 revisions as `cat-file.c`, was renamed to `builtin/cat-file.c` |
126640af JS |
4282 | when made a builtin, and then saw less than 10 versions). |
4283 | ||
09b7e220 | 4284 | So, look into `builtin/cat-file.c`, search for `cmd_cat_file()` and look what |
126640af JS |
4285 | it does. |
4286 | ||
4287 | ------------------------------------------------------------------ | |
4288 | git_config(git_default_config); | |
4289 | if (argc != 3) | |
6127c086 | 4290 | usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>"); |
126640af JS |
4291 | if (get_sha1(argv[2], sha1)) |
4292 | die("Not a valid object name %s", argv[2]); | |
4293 | ------------------------------------------------------------------ | |
4294 | ||
4295 | Let's skip over the obvious details; the only really interesting part | |
4296 | here is the call to `get_sha1()`. It tries to interpret `argv[2]` as an | |
4297 | object name, and if it refers to an object which is present in the current | |
4298 | repository, it writes the resulting SHA-1 into the variable `sha1`. | |
4299 | ||
4300 | Two things are interesting here: | |
4301 | ||
4302 | - `get_sha1()` returns 0 on _success_. This might surprise some new | |
4303 | Git hackers, but there is a long tradition in UNIX to return different | |
2ef8ac1b | 4304 | negative numbers in case of different errors--and 0 on success. |
126640af JS |
4305 | |
4306 | - the variable `sha1` in the function signature of `get_sha1()` is `unsigned | |
6cf378f0 | 4307 | char *`, but is actually expected to be a pointer to `unsigned |
126640af | 4308 | char[20]`. This variable will contain the 160-bit SHA-1 of the given |
6cf378f0 | 4309 | commit. Note that whenever a SHA-1 is passed as `unsigned char *`, it |
126640af | 4310 | is the binary representation, as opposed to the ASCII representation in |
a5fc33b4 | 4311 | hex characters, which is passed as `char *`. |
126640af JS |
4312 | |
4313 | You will see both of these things throughout the code. | |
4314 | ||
4315 | Now, for the meat: | |
4316 | ||
4317 | ----------------------------------------------------------------------------- | |
4318 | case 0: | |
4319 | buf = read_object_with_reference(sha1, argv[1], &size, NULL); | |
4320 | ----------------------------------------------------------------------------- | |
4321 | ||
4322 | This is how you read a blob (actually, not only a blob, but any type of | |
4323 | object). To know how the function `read_object_with_reference()` actually | |
4324 | works, find the source code for it (something like `git grep | |
2de9b711 | 4325 | read_object_with | grep ":[a-z]"` in the Git repository), and read |
126640af JS |
4326 | the source. |
4327 | ||
4328 | To find out how the result can be used, just read on in `cmd_cat_file()`: | |
4329 | ||
4330 | ----------------------------------- | |
4331 | write_or_die(1, buf, size); | |
4332 | ----------------------------------- | |
4333 | ||
4334 | Sometimes, you do not know where to look for a feature. In many such cases, | |
6127c086 | 4335 | it helps to search through the output of `git log`, and then `git show` the |
126640af JS |
4336 | corresponding commit. |
4337 | ||
6127c086 | 4338 | Example: If you know that there was some test case for `git bundle`, but |
126640af JS |
4339 | do not remember where it was (yes, you _could_ `git grep bundle t/`, but that |
4340 | does not illustrate the point!): | |
4341 | ||
4342 | ------------------------ | |
4343 | $ git log --no-merges t/ | |
4344 | ------------------------ | |
4345 | ||
4346 | In the pager (`less`), just search for "bundle", go a few lines back, | |
4347 | and see that it is in commit 18449ab0... Now just copy this object name, | |
4348 | and paste it into the command line | |
4349 | ||
4350 | ------------------- | |
4351 | $ git show 18449ab0 | |
4352 | ------------------- | |
4353 | ||
4354 | Voila. | |
4355 | ||
4356 | Another example: Find out what to do in order to make some script a | |
4357 | builtin: | |
4358 | ||
4359 | ------------------------------------------------- | |
09b7e220 | 4360 | $ git log --no-merges --diff-filter=A builtin/*.c |
126640af JS |
4361 | ------------------------------------------------- |
4362 | ||
4363 | You see, Git is actually the best tool to find out about the source of Git | |
4364 | itself! | |
4365 | ||
e34caace | 4366 | [[glossary]] |
73a1d050 | 4367 | Git Glossary |
497c8331 CC |
4368 | ============ |
4369 | ||
4370 | include::glossary-content.txt[] | |
d19fbc3c | 4371 | |
2624d9a5 | 4372 | [[git-quick-start]] |
99f171bb BF |
4373 | Appendix A: Git Quick Reference |
4374 | =============================== | |
2624d9a5 | 4375 | |
99f171bb BF |
4376 | This is a quick summary of the major commands; the previous chapters |
4377 | explain how these work in more detail. | |
2624d9a5 BF |
4378 | |
4379 | [[quick-creating-a-new-repository]] | |
4380 | Creating a new repository | |
4381 | ------------------------- | |
4382 | ||
4383 | From a tarball: | |
4384 | ||
4385 | ----------------------------------------------- | |
4386 | $ tar xzf project.tar.gz | |
4387 | $ cd project | |
4388 | $ git init | |
4389 | Initialized empty Git repository in .git/ | |
4390 | $ git add . | |
4391 | $ git commit | |
4392 | ----------------------------------------------- | |
4393 | ||
4394 | From a remote repository: | |
4395 | ||
4396 | ----------------------------------------------- | |
4397 | $ git clone git://example.com/pub/project.git | |
4398 | $ cd project | |
4399 | ----------------------------------------------- | |
4400 | ||
4401 | [[managing-branches]] | |
4402 | Managing branches | |
4403 | ----------------- | |
4404 | ||
4405 | ----------------------------------------------- | |
4406 | $ git branch # list all local branches in this repo | |
4407 | $ git checkout test # switch working directory to branch "test" | |
4408 | $ git branch new # create branch "new" starting at current HEAD | |
4409 | $ git branch -d new # delete branch "new" | |
4410 | ----------------------------------------------- | |
4411 | ||
06ada152 | 4412 | Instead of basing a new branch on current HEAD (the default), use: |
2624d9a5 BF |
4413 | |
4414 | ----------------------------------------------- | |
4415 | $ git branch new test # branch named "test" | |
4416 | $ git branch new v2.6.15 # tag named v2.6.15 | |
4417 | $ git branch new HEAD^ # commit before the most recent | |
4418 | $ git branch new HEAD^^ # commit before that | |
4419 | $ git branch new test~10 # ten commits before tip of branch "test" | |
4420 | ----------------------------------------------- | |
4421 | ||
4422 | Create and switch to a new branch at the same time: | |
4423 | ||
4424 | ----------------------------------------------- | |
4425 | $ git checkout -b new v2.6.15 | |
4426 | ----------------------------------------------- | |
4427 | ||
4428 | Update and examine branches from the repository you cloned from: | |
4429 | ||
4430 | ----------------------------------------------- | |
4431 | $ git fetch # update | |
4432 | $ git branch -r # list | |
4433 | origin/master | |
4434 | origin/next | |
4435 | ... | |
4436 | $ git checkout -b masterwork origin/master | |
4437 | ----------------------------------------------- | |
4438 | ||
4439 | Fetch a branch from a different repository, and give it a new | |
4440 | name in your repository: | |
4441 | ||
4442 | ----------------------------------------------- | |
4443 | $ git fetch git://example.com/project.git theirbranch:mybranch | |
4444 | $ git fetch git://example.com/project.git v2.6.15:mybranch | |
4445 | ----------------------------------------------- | |
4446 | ||
4447 | Keep a list of repositories you work with regularly: | |
4448 | ||
4449 | ----------------------------------------------- | |
4450 | $ git remote add example git://example.com/project.git | |
4451 | $ git remote # list remote repositories | |
4452 | example | |
4453 | origin | |
4454 | $ git remote show example # get details | |
4455 | * remote example | |
4456 | URL: git://example.com/project.git | |
4457 | Tracked remote branches | |
20244ea2 JS |
4458 | master |
4459 | next | |
4460 | ... | |
2624d9a5 BF |
4461 | $ git fetch example # update branches from example |
4462 | $ git branch -r # list all remote branches | |
4463 | ----------------------------------------------- | |
4464 | ||
4465 | ||
4466 | [[exploring-history]] | |
4467 | Exploring history | |
4468 | ----------------- | |
4469 | ||
4470 | ----------------------------------------------- | |
4471 | $ gitk # visualize and browse history | |
4472 | $ git log # list all commits | |
4473 | $ git log src/ # ...modifying src/ | |
4474 | $ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15 | |
4475 | $ git log master..test # ...in branch test, not in branch master | |
4476 | $ git log test..master # ...in branch master, but not in test | |
4477 | $ git log test...master # ...in one branch, not in both | |
4478 | $ git log -S'foo()' # ...where difference contain "foo()" | |
4479 | $ git log --since="2 weeks ago" | |
4480 | $ git log -p # show patches as well | |
4481 | $ git show # most recent commit | |
4482 | $ git diff v2.6.15..v2.6.16 # diff between two tagged versions | |
4483 | $ git diff v2.6.15..HEAD # diff with current head | |
4484 | $ git grep "foo()" # search working directory for "foo()" | |
4485 | $ git grep v2.6.15 "foo()" # search old tree for "foo()" | |
4486 | $ git show v2.6.15:a.txt # look at old version of a.txt | |
4487 | ----------------------------------------------- | |
4488 | ||
4489 | Search for regressions: | |
4490 | ||
4491 | ----------------------------------------------- | |
4492 | $ git bisect start | |
4493 | $ git bisect bad # current version is bad | |
4494 | $ git bisect good v2.6.13-rc2 # last known good revision | |
4495 | Bisecting: 675 revisions left to test after this | |
4496 | # test here, then: | |
4497 | $ git bisect good # if this revision is good, or | |
4498 | $ git bisect bad # if this revision is bad. | |
4499 | # repeat until done. | |
4500 | ----------------------------------------------- | |
4501 | ||
4502 | [[making-changes]] | |
4503 | Making changes | |
4504 | -------------- | |
4505 | ||
2de9b711 | 4506 | Make sure Git knows who to blame: |
2624d9a5 BF |
4507 | |
4508 | ------------------------------------------------ | |
4509 | $ cat >>~/.gitconfig <<\EOF | |
4510 | [user] | |
4511 | name = Your Name Comes Here | |
4512 | email = you@yourdomain.example.com | |
4513 | EOF | |
4514 | ------------------------------------------------ | |
4515 | ||
4516 | Select file contents to include in the next commit, then make the | |
4517 | commit: | |
4518 | ||
4519 | ----------------------------------------------- | |
4520 | $ git add a.txt # updated file | |
4521 | $ git add b.txt # new file | |
4522 | $ git rm c.txt # old file | |
4523 | $ git commit | |
4524 | ----------------------------------------------- | |
4525 | ||
4526 | Or, prepare and create the commit in one step: | |
4527 | ||
4528 | ----------------------------------------------- | |
4529 | $ git commit d.txt # use latest content only of d.txt | |
4530 | $ git commit -a # use latest content of all tracked files | |
4531 | ----------------------------------------------- | |
4532 | ||
4533 | [[merging]] | |
4534 | Merging | |
4535 | ------- | |
4536 | ||
4537 | ----------------------------------------------- | |
4538 | $ git merge test # merge branch "test" into the current branch | |
4539 | $ git pull git://example.com/project.git master | |
4540 | # fetch and merge in remote branch | |
4541 | $ git pull . test # equivalent to git merge test | |
4542 | ----------------------------------------------- | |
4543 | ||
4544 | [[sharing-your-changes]] | |
4545 | Sharing your changes | |
4546 | -------------------- | |
4547 | ||
4548 | Importing or exporting patches: | |
4549 | ||
4550 | ----------------------------------------------- | |
4551 | $ git format-patch origin..HEAD # format a patch for each commit | |
4552 | # in HEAD but not in origin | |
4553 | $ git am mbox # import patches from the mailbox "mbox" | |
4554 | ----------------------------------------------- | |
4555 | ||
2de9b711 | 4556 | Fetch a branch in a different Git repository, then merge into the |
2624d9a5 BF |
4557 | current branch: |
4558 | ||
4559 | ----------------------------------------------- | |
4560 | $ git pull git://example.com/project.git theirbranch | |
4561 | ----------------------------------------------- | |
4562 | ||
4563 | Store the fetched branch into a local branch before merging into the | |
4564 | current branch: | |
4565 | ||
4566 | ----------------------------------------------- | |
4567 | $ git pull git://example.com/project.git theirbranch:mybranch | |
4568 | ----------------------------------------------- | |
4569 | ||
4570 | After creating commits on a local branch, update the remote | |
4571 | branch with your commits: | |
4572 | ||
4573 | ----------------------------------------------- | |
4574 | $ git push ssh://example.com/project.git mybranch:theirbranch | |
4575 | ----------------------------------------------- | |
4576 | ||
4577 | When remote and local branch are both named "test": | |
4578 | ||
4579 | ----------------------------------------------- | |
4580 | $ git push ssh://example.com/project.git test | |
4581 | ----------------------------------------------- | |
4582 | ||
4583 | Shortcut version for a frequently used remote repository: | |
4584 | ||
4585 | ----------------------------------------------- | |
4586 | $ git remote add example ssh://example.com/project.git | |
4587 | $ git push example test | |
4588 | ----------------------------------------------- | |
4589 | ||
4590 | [[repository-maintenance]] | |
4591 | Repository maintenance | |
4592 | ---------------------- | |
4593 | ||
4594 | Check for corruption: | |
4595 | ||
4596 | ----------------------------------------------- | |
4597 | $ git fsck | |
4598 | ----------------------------------------------- | |
4599 | ||
4600 | Recompress, remove unused cruft: | |
4601 | ||
4602 | ----------------------------------------------- | |
4603 | $ git gc | |
4604 | ----------------------------------------------- | |
4605 | ||
4606 | ||
e34caace | 4607 | [[todo]] |
2624d9a5 BF |
4608 | Appendix B: Notes and todo list for this manual |
4609 | =============================================== | |
6bd9b682 BF |
4610 | |
4611 | This is a work in progress. | |
4612 | ||
4613 | The basic requirements: | |
ecd95b53 BF |
4614 | |
4615 | - It must be readable in order, from beginning to end, by someone | |
4616 | intelligent with a basic grasp of the UNIX command line, but without | |
2de9b711 | 4617 | any special knowledge of Git. If necessary, any other prerequisites |
ecd95b53 BF |
4618 | should be specifically mentioned as they arise. |
4619 | - Whenever possible, section headings should clearly describe the task | |
4620 | they explain how to do, in language that requires no more knowledge | |
4621 | than necessary: for example, "importing patches into a project" rather | |
6127c086 | 4622 | than "the `git am` command" |
6bd9b682 | 4623 | |
d5cd5de4 BF |
4624 | Think about how to create a clear chapter dependency graph that will |
4625 | allow people to get to important topics without necessarily reading | |
4626 | everything in between. | |
d19fbc3c | 4627 | |
1249d8ad | 4628 | Scan `Documentation/` for other stuff left out; in particular: |
ecd95b53 BF |
4629 | |
4630 | - howto's | |
1249d8ad | 4631 | - some of `technical/`? |
ecd95b53 | 4632 | - hooks |
5162e697 | 4633 | - list of commands in linkgit:git[1] |
d19fbc3c BF |
4634 | |
4635 | Scan email archives for other stuff left out | |
4636 | ||
4637 | Scan man pages to see if any assume more background than this manual | |
4638 | provides. | |
4639 | ||
2f99710c | 4640 | Simplify beginning by suggesting disconnected head instead of |
b181d57f | 4641 | temporary branch creation? |
d19fbc3c | 4642 | |
2f99710c BF |
4643 | Add more good examples. Entire sections of just cookbook examples |
4644 | might be a good idea; maybe make an "advanced examples" section a | |
4645 | standard end-of-chapter section? | |
d19fbc3c BF |
4646 | |
4647 | Include cross-references to the glossary, where appropriate. | |
4648 | ||
9a241220 BF |
4649 | Document shallow clones? See draft 1.5.0 release notes for some |
4650 | documentation. | |
4651 | ||
3dff5379 | 4652 | Add a section on working with other version control systems, including |
9a241220 BF |
4653 | CVS, Subversion, and just imports of series of release tarballs. |
4654 | ||
a8cd1402 | 4655 | More details on gitweb? |
0b375ab0 BF |
4656 | |
4657 | Write a chapter on using plumbing and writing scripts. | |
d9bd321c BF |
4658 | |
4659 | Alternates, clone -reference, etc. | |
4660 | ||
1cdade2c | 4661 | More on recovery from repository corruption. See: |
efe6de6e OB |
4662 | http://marc.info/?l=git&m=117263864820799&w=2 |
4663 | http://marc.info/?l=git&m=117147855503798&w=2 |