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0eb4f7cd | 1 | Git User's Manual (for version 1.5.3 or newer) |
71f4b183 | 2 | ______________________________________________ |
d19fbc3c | 3 | |
99eaefdd BF |
4 | |
5 | Git is a fast distributed revision control system. | |
6 | ||
02783075 | 7 | This manual is designed to be readable by someone with basic UNIX |
2de9b711 | 8 | command-line skills, but no previous knowledge of Git. |
d19fbc3c | 9 | |
2624d9a5 BF |
10 | <<repositories-and-branches>> and <<exploring-git-history>> explain how |
11 | to fetch and study a project using git--read these chapters to learn how | |
12 | to build and test a particular version of a software project, search for | |
13 | regressions, and so on. | |
ef89f701 | 14 | |
2624d9a5 | 15 | People needing to do actual development will also want to read |
aa971cb9 | 16 | <<Developing-With-git>> and <<sharing-development>>. |
6bd9b682 BF |
17 | |
18 | Further chapters cover more specialized topics. | |
19 | ||
d19fbc3c | 20 | Comprehensive reference documentation is available through the man |
b3d98887 | 21 | pages, or linkgit:git-help[1] command. For example, for the command |
1249d8ad | 22 | `git clone <repo>`, you can either use: |
d19fbc3c BF |
23 | |
24 | ------------------------------------------------ | |
25 | $ man git-clone | |
26 | ------------------------------------------------ | |
27 | ||
b3d98887 CC |
28 | or: |
29 | ||
30 | ------------------------------------------------ | |
31 | $ git help clone | |
32 | ------------------------------------------------ | |
33 | ||
34 | With the latter, you can use the manual viewer of your choice; see | |
35 | linkgit:git-help[1] for more information. | |
36 | ||
2de9b711 | 37 | See also <<git-quick-start>> for a brief overview of Git commands, |
2624d9a5 | 38 | without any explanation. |
b181d57f | 39 | |
99f171bb | 40 | Finally, see <<todo>> for ways that you can help make this manual more |
2624d9a5 | 41 | complete. |
b181d57f | 42 | |
b181d57f | 43 | |
e34caace | 44 | [[repositories-and-branches]] |
d19fbc3c BF |
45 | Repositories and Branches |
46 | ========================= | |
47 | ||
e34caace | 48 | [[how-to-get-a-git-repository]] |
2de9b711 | 49 | How to get a Git repository |
d19fbc3c BF |
50 | --------------------------- |
51 | ||
2de9b711 | 52 | It will be useful to have a Git repository to experiment with as you |
d19fbc3c BF |
53 | read this manual. |
54 | ||
5162e697 | 55 | The best way to get one is by using the linkgit:git-clone[1] command to |
a5f90f31 BF |
56 | download a copy of an existing repository. If you don't already have a |
57 | project in mind, here are some interesting examples: | |
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58 | |
59 | ------------------------------------------------ | |
4b9ced27 | 60 | # Git itself (approx. 40MB download): |
d19fbc3c | 61 | $ git clone git://git.kernel.org/pub/scm/git/git.git |
4b9ced27 TK |
62 | # the Linux kernel (approx. 640MB download): |
63 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git | |
d19fbc3c BF |
64 | ------------------------------------------------ |
65 | ||
66 | The initial clone may be time-consuming for a large project, but you | |
67 | will only need to clone once. | |
68 | ||
283efb01 TK |
69 | The clone command creates a new directory named after the project |
70 | (`git` or `linux` in the examples above). After you cd into this | |
d19fbc3c | 71 | directory, you will see that it contains a copy of the project files, |
0c4a33b5 | 72 | called the <<def_working_tree,working tree>>, together with a special |
1249d8ad | 73 | top-level directory named `.git`, which contains all the information |
0c4a33b5 | 74 | about the history of the project. |
d19fbc3c | 75 | |
e34caace | 76 | [[how-to-check-out]] |
d19fbc3c BF |
77 | How to check out a different version of a project |
78 | ------------------------------------------------- | |
79 | ||
a2ef9d63 BF |
80 | Git is best thought of as a tool for storing the history of a collection |
81 | of files. It stores the history as a compressed collection of | |
2de9b711 | 82 | interrelated snapshots of the project's contents. In Git each such |
a2ef9d63 | 83 | version is called a <<def_commit,commit>>. |
d19fbc3c | 84 | |
0c4a33b5 BF |
85 | Those snapshots aren't necessarily all arranged in a single line from |
86 | oldest to newest; instead, work may simultaneously proceed along | |
57283291 | 87 | parallel lines of development, called <<def_branch,branches>>, which may |
0c4a33b5 BF |
88 | merge and diverge. |
89 | ||
2de9b711 | 90 | A single Git repository can track development on multiple branches. It |
0c4a33b5 | 91 | does this by keeping a list of <<def_head,heads>> which reference the |
5162e697 | 92 | latest commit on each branch; the linkgit:git-branch[1] command shows |
81b6c950 | 93 | you the list of branch heads: |
d19fbc3c BF |
94 | |
95 | ------------------------------------------------ | |
96 | $ git branch | |
97 | * master | |
98 | ------------------------------------------------ | |
99 | ||
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100 | A freshly cloned repository contains a single branch head, by default |
101 | named "master", with the working directory initialized to the state of | |
102 | the project referred to by that branch head. | |
d19fbc3c | 103 | |
81b6c950 BF |
104 | Most projects also use <<def_tag,tags>>. Tags, like heads, are |
105 | references into the project's history, and can be listed using the | |
5162e697 | 106 | linkgit:git-tag[1] command: |
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107 | |
108 | ------------------------------------------------ | |
109 | $ git tag -l | |
110 | v2.6.11 | |
111 | v2.6.11-tree | |
112 | v2.6.12 | |
113 | v2.6.12-rc2 | |
114 | v2.6.12-rc3 | |
115 | v2.6.12-rc4 | |
116 | v2.6.12-rc5 | |
117 | v2.6.12-rc6 | |
118 | v2.6.13 | |
119 | ... | |
120 | ------------------------------------------------ | |
121 | ||
fe4b3e59 | 122 | Tags are expected to always point at the same version of a project, |
81b6c950 | 123 | while heads are expected to advance as development progresses. |
fe4b3e59 | 124 | |
81b6c950 | 125 | Create a new branch head pointing to one of these versions and check it |
5162e697 | 126 | out using linkgit:git-checkout[1]: |
d19fbc3c BF |
127 | |
128 | ------------------------------------------------ | |
129 | $ git checkout -b new v2.6.13 | |
130 | ------------------------------------------------ | |
131 | ||
132 | The working directory then reflects the contents that the project had | |
5162e697 | 133 | when it was tagged v2.6.13, and linkgit:git-branch[1] shows two |
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134 | branches, with an asterisk marking the currently checked-out branch: |
135 | ||
136 | ------------------------------------------------ | |
137 | $ git branch | |
138 | master | |
139 | * new | |
140 | ------------------------------------------------ | |
141 | ||
142 | If you decide that you'd rather see version 2.6.17, you can modify | |
143 | the current branch to point at v2.6.17 instead, with | |
144 | ||
145 | ------------------------------------------------ | |
146 | $ git reset --hard v2.6.17 | |
147 | ------------------------------------------------ | |
148 | ||
81b6c950 | 149 | Note that if the current branch head was your only reference to a |
d19fbc3c | 150 | particular point in history, then resetting that branch may leave you |
81b6c950 BF |
151 | with no way to find the history it used to point to; so use this command |
152 | carefully. | |
d19fbc3c | 153 | |
e34caace | 154 | [[understanding-commits]] |
d19fbc3c BF |
155 | Understanding History: Commits |
156 | ------------------------------ | |
157 | ||
158 | Every change in the history of a project is represented by a commit. | |
5162e697 | 159 | The linkgit:git-show[1] command shows the most recent commit on the |
d19fbc3c BF |
160 | current branch: |
161 | ||
162 | ------------------------------------------------ | |
163 | $ git show | |
e2618ff4 BF |
164 | commit 17cf781661e6d38f737f15f53ab552f1e95960d7 |
165 | Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)> | |
166 | Date: Tue Apr 19 14:11:06 2005 -0700 | |
167 | ||
168 | Remove duplicate getenv(DB_ENVIRONMENT) call | |
169 | ||
170 | Noted by Tony Luck. | |
171 | ||
172 | diff --git a/init-db.c b/init-db.c | |
173 | index 65898fa..b002dc6 100644 | |
174 | --- a/init-db.c | |
175 | +++ b/init-db.c | |
176 | @@ -7,7 +7,7 @@ | |
d19fbc3c | 177 | |
e2618ff4 BF |
178 | int main(int argc, char **argv) |
179 | { | |
180 | - char *sha1_dir = getenv(DB_ENVIRONMENT), *path; | |
181 | + char *sha1_dir, *path; | |
182 | int len, i; | |
183 | ||
184 | if (mkdir(".git", 0755) < 0) { | |
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185 | ------------------------------------------------ |
186 | ||
187 | As you can see, a commit shows who made the latest change, what they | |
188 | did, and why. | |
189 | ||
35121930 | 190 | Every commit has a 40-hexdigit id, sometimes called the "object name" or the |
1249d8ad | 191 | "SHA-1 id", shown on the first line of the `git show` output. You can usually |
35121930 BF |
192 | refer to a commit by a shorter name, such as a tag or a branch name, but this |
193 | longer name can also be useful. Most importantly, it is a globally unique | |
194 | name for this commit: so if you tell somebody else the object name (for | |
195 | example in email), then you are guaranteed that name will refer to the same | |
196 | commit in their repository that it does in yours (assuming their repository | |
197 | has that commit at all). Since the object name is computed as a hash over the | |
198 | contents of the commit, you are guaranteed that the commit can never change | |
199 | without its name also changing. | |
200 | ||
2de9b711 | 201 | In fact, in <<git-concepts>> we shall see that everything stored in Git |
35121930 BF |
202 | history, including file data and directory contents, is stored in an object |
203 | with a name that is a hash of its contents. | |
d19fbc3c | 204 | |
e34caace | 205 | [[understanding-reachability]] |
d19fbc3c BF |
206 | Understanding history: commits, parents, and reachability |
207 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
208 | ||
209 | Every commit (except the very first commit in a project) also has a | |
210 | parent commit which shows what happened before this commit. | |
211 | Following the chain of parents will eventually take you back to the | |
212 | beginning of the project. | |
213 | ||
2de9b711 | 214 | However, the commits do not form a simple list; Git allows lines of |
d19fbc3c BF |
215 | development to diverge and then reconverge, and the point where two |
216 | lines of development reconverge is called a "merge". The commit | |
217 | representing a merge can therefore have more than one parent, with | |
218 | each parent representing the most recent commit on one of the lines | |
219 | of development leading to that point. | |
220 | ||
5162e697 | 221 | The best way to see how this works is using the linkgit:gitk[1] |
2de9b711 TA |
222 | command; running gitk now on a Git repository and looking for merge |
223 | commits will help understand how the Git organizes history. | |
d19fbc3c BF |
224 | |
225 | In the following, we say that commit X is "reachable" from commit Y | |
226 | if commit X is an ancestor of commit Y. Equivalently, you could say | |
02783075 | 227 | that Y is a descendant of X, or that there is a chain of parents |
d19fbc3c BF |
228 | leading from commit Y to commit X. |
229 | ||
e34caace | 230 | [[history-diagrams]] |
3dff5379 PR |
231 | Understanding history: History diagrams |
232 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 233 | |
2de9b711 | 234 | We will sometimes represent Git history using diagrams like the one |
d19fbc3c BF |
235 | below. Commits are shown as "o", and the links between them with |
236 | lines drawn with - / and \. Time goes left to right: | |
237 | ||
1dc71a91 BF |
238 | |
239 | ................................................ | |
d19fbc3c BF |
240 | o--o--o <-- Branch A |
241 | / | |
242 | o--o--o <-- master | |
243 | \ | |
244 | o--o--o <-- Branch B | |
1dc71a91 | 245 | ................................................ |
d19fbc3c BF |
246 | |
247 | If we need to talk about a particular commit, the character "o" may | |
248 | be replaced with another letter or number. | |
249 | ||
e34caace | 250 | [[what-is-a-branch]] |
d19fbc3c BF |
251 | Understanding history: What is a branch? |
252 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
253 | ||
81b6c950 BF |
254 | When we need to be precise, we will use the word "branch" to mean a line |
255 | of development, and "branch head" (or just "head") to mean a reference | |
256 | to the most recent commit on a branch. In the example above, the branch | |
257 | head named "A" is a pointer to one particular commit, but we refer to | |
258 | the line of three commits leading up to that point as all being part of | |
d19fbc3c BF |
259 | "branch A". |
260 | ||
81b6c950 BF |
261 | However, when no confusion will result, we often just use the term |
262 | "branch" both for branches and for branch heads. | |
d19fbc3c | 263 | |
e34caace | 264 | [[manipulating-branches]] |
d19fbc3c BF |
265 | Manipulating branches |
266 | --------------------- | |
267 | ||
268 | Creating, deleting, and modifying branches is quick and easy; here's | |
269 | a summary of the commands: | |
270 | ||
1249d8ad | 271 | `git branch`:: |
d19fbc3c | 272 | list all branches |
1249d8ad TK |
273 | `git branch <branch>`:: |
274 | create a new branch named `<branch>`, referencing the same | |
d19fbc3c | 275 | point in history as the current branch |
1249d8ad TK |
276 | `git branch <branch> <start-point>`:: |
277 | create a new branch named `<branch>`, referencing | |
278 | `<start-point>`, which may be specified any way you like, | |
d19fbc3c | 279 | including using a branch name or a tag name |
1249d8ad TK |
280 | `git branch -d <branch>`:: |
281 | delete the branch `<branch>`; if the branch you are deleting | |
c64415e2 BF |
282 | points to a commit which is not reachable from the current |
283 | branch, this command will fail with a warning. | |
1249d8ad | 284 | `git branch -D <branch>`:: |
d19fbc3c BF |
285 | even if the branch points to a commit not reachable |
286 | from the current branch, you may know that that commit | |
287 | is still reachable from some other branch or tag. In that | |
2de9b711 | 288 | case it is safe to use this command to force Git to delete |
d19fbc3c | 289 | the branch. |
1249d8ad TK |
290 | `git checkout <branch>`:: |
291 | make the current branch `<branch>`, updating the working | |
292 | directory to reflect the version referenced by `<branch>` | |
293 | `git checkout -b <new> <start-point>`:: | |
294 | create a new branch `<new>` referencing `<start-point>`, and | |
d19fbc3c BF |
295 | check it out. |
296 | ||
72a76c95 | 297 | The special symbol "HEAD" can always be used to refer to the current |
1249d8ad TK |
298 | branch. In fact, Git uses a file named `HEAD` in the `.git` directory |
299 | to remember which branch is current: | |
72a76c95 BF |
300 | |
301 | ------------------------------------------------ | |
302 | $ cat .git/HEAD | |
303 | ref: refs/heads/master | |
304 | ------------------------------------------------ | |
305 | ||
25d9f3fa | 306 | [[detached-head]] |
72a76c95 BF |
307 | Examining an old version without creating a new branch |
308 | ------------------------------------------------------ | |
309 | ||
6127c086 | 310 | The `git checkout` command normally expects a branch head, but will also |
72a76c95 BF |
311 | accept an arbitrary commit; for example, you can check out the commit |
312 | referenced by a tag: | |
313 | ||
314 | ------------------------------------------------ | |
315 | $ git checkout v2.6.17 | |
316 | Note: moving to "v2.6.17" which isn't a local branch | |
317 | If you want to create a new branch from this checkout, you may do so | |
318 | (now or later) by using -b with the checkout command again. Example: | |
319 | git checkout -b <new_branch_name> | |
320 | HEAD is now at 427abfa... Linux v2.6.17 | |
321 | ------------------------------------------------ | |
322 | ||
a6e5ef7d | 323 | The HEAD then refers to the SHA-1 of the commit instead of to a branch, |
72a76c95 BF |
324 | and git branch shows that you are no longer on a branch: |
325 | ||
326 | ------------------------------------------------ | |
327 | $ cat .git/HEAD | |
328 | 427abfa28afedffadfca9dd8b067eb6d36bac53f | |
953f3d6f | 329 | $ git branch |
72a76c95 BF |
330 | * (no branch) |
331 | master | |
332 | ------------------------------------------------ | |
333 | ||
334 | In this case we say that the HEAD is "detached". | |
335 | ||
953f3d6f BF |
336 | This is an easy way to check out a particular version without having to |
337 | make up a name for the new branch. You can still create a new branch | |
338 | (or tag) for this version later if you decide to. | |
d19fbc3c | 339 | |
e34caace | 340 | [[examining-remote-branches]] |
d19fbc3c BF |
341 | Examining branches from a remote repository |
342 | ------------------------------------------- | |
343 | ||
344 | The "master" branch that was created at the time you cloned is a copy | |
345 | of the HEAD in the repository that you cloned from. That repository | |
346 | may also have had other branches, though, and your local repository | |
66a062a1 MM |
347 | keeps branches which track each of those remote branches, called |
348 | remote-tracking branches, which you | |
1249d8ad | 349 | can view using the `-r` option to linkgit:git-branch[1]: |
d19fbc3c BF |
350 | |
351 | ------------------------------------------------ | |
352 | $ git branch -r | |
353 | origin/HEAD | |
354 | origin/html | |
355 | origin/maint | |
356 | origin/man | |
357 | origin/master | |
358 | origin/next | |
359 | origin/pu | |
360 | origin/todo | |
361 | ------------------------------------------------ | |
362 | ||
66a062a1 MM |
363 | In this example, "origin" is called a remote repository, or "remote" |
364 | for short. The branches of this repository are called "remote | |
365 | branches" from our point of view. The remote-tracking branches listed | |
366 | above were created based on the remote branches at clone time and will | |
1249d8ad | 367 | be updated by `git fetch` (hence `git pull`) and `git push`. See |
66a062a1 MM |
368 | <<Updating-a-repository-With-git-fetch>> for details. |
369 | ||
45dfd403 JN |
370 | You might want to build on one of these remote-tracking branches |
371 | on a branch of your own, just as you would for a tag: | |
d19fbc3c BF |
372 | |
373 | ------------------------------------------------ | |
374 | $ git checkout -b my-todo-copy origin/todo | |
375 | ------------------------------------------------ | |
376 | ||
1249d8ad | 377 | You can also check out `origin/todo` directly to examine it or |
45dfd403 JN |
378 | write a one-off patch. See <<detached-head,detached head>>. |
379 | ||
2de9b711 | 380 | Note that the name "origin" is just the name that Git uses by default |
d19fbc3c BF |
381 | to refer to the repository that you cloned from. |
382 | ||
383 | [[how-git-stores-references]] | |
f60b9642 BF |
384 | Naming branches, tags, and other references |
385 | ------------------------------------------- | |
d19fbc3c BF |
386 | |
387 | Branches, remote-tracking branches, and tags are all references to | |
f60b9642 | 388 | commits. All references are named with a slash-separated path name |
1249d8ad | 389 | starting with `refs`; the names we've been using so far are actually |
f60b9642 | 390 | shorthand: |
d19fbc3c | 391 | |
1249d8ad TK |
392 | - The branch `test` is short for `refs/heads/test`. |
393 | - The tag `v2.6.18` is short for `refs/tags/v2.6.18`. | |
394 | - `origin/master` is short for `refs/remotes/origin/master`. | |
d19fbc3c | 395 | |
f60b9642 BF |
396 | The full name is occasionally useful if, for example, there ever |
397 | exists a tag and a branch with the same name. | |
d19fbc3c | 398 | |
1249d8ad | 399 | (Newly created refs are actually stored in the `.git/refs` directory, |
fc74ecc1 BF |
400 | under the path given by their name. However, for efficiency reasons |
401 | they may also be packed together in a single file; see | |
5162e697 | 402 | linkgit:git-pack-refs[1]). |
fc74ecc1 | 403 | |
c64415e2 BF |
404 | As another useful shortcut, the "HEAD" of a repository can be referred |
405 | to just using the name of that repository. So, for example, "origin" | |
406 | is usually a shortcut for the HEAD branch in the repository "origin". | |
d19fbc3c | 407 | |
2de9b711 | 408 | For the complete list of paths which Git checks for references, and |
f60b9642 BF |
409 | the order it uses to decide which to choose when there are multiple |
410 | references with the same shorthand name, see the "SPECIFYING | |
9d83e382 | 411 | REVISIONS" section of linkgit:gitrevisions[7]. |
d19fbc3c | 412 | |
aa971cb9 | 413 | [[Updating-a-repository-With-git-fetch]] |
6127c086 | 414 | Updating a repository with git fetch |
d19fbc3c BF |
415 | ------------------------------------ |
416 | ||
417 | Eventually the developer cloned from will do additional work in her | |
418 | repository, creating new commits and advancing the branches to point | |
419 | at the new commits. | |
420 | ||
1249d8ad | 421 | The command `git fetch`, with no arguments, will update all of the |
d19fbc3c BF |
422 | remote-tracking branches to the latest version found in her |
423 | repository. It will not touch any of your own branches--not even the | |
424 | "master" branch that was created for you on clone. | |
425 | ||
e34caace | 426 | [[fetching-branches]] |
d5cd5de4 BF |
427 | Fetching branches from other repositories |
428 | ----------------------------------------- | |
429 | ||
430 | You can also track branches from repositories other than the one you | |
5162e697 | 431 | cloned from, using linkgit:git-remote[1]: |
d5cd5de4 BF |
432 | |
433 | ------------------------------------------------- | |
34a25d4c TK |
434 | $ git remote add staging git://git.kernel.org/.../gregkh/staging.git |
435 | $ git fetch staging | |
436 | ... | |
437 | From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging | |
438 | * [new branch] master -> staging/master | |
439 | * [new branch] staging-linus -> staging/staging-linus | |
440 | * [new branch] staging-next -> staging/staging-next | |
d5cd5de4 BF |
441 | ------------------------------------------------- |
442 | ||
443 | New remote-tracking branches will be stored under the shorthand name | |
34a25d4c | 444 | that you gave `git remote add`, in this case `staging`: |
d5cd5de4 BF |
445 | |
446 | ------------------------------------------------- | |
447 | $ git branch -r | |
34a25d4c TK |
448 | origin/HEAD -> origin/master |
449 | origin/master | |
450 | staging/master | |
451 | staging/staging-linus | |
452 | staging/staging-next | |
d5cd5de4 BF |
453 | ------------------------------------------------- |
454 | ||
1249d8ad TK |
455 | If you run `git fetch <remote>` later, the remote-tracking branches |
456 | for the named `<remote>` will be updated. | |
d5cd5de4 | 457 | |
1249d8ad | 458 | If you examine the file `.git/config`, you will see that Git has added |
d5cd5de4 BF |
459 | a new stanza: |
460 | ||
461 | ------------------------------------------------- | |
462 | $ cat .git/config | |
463 | ... | |
34a25d4c TK |
464 | [remote "staging"] |
465 | url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git | |
466 | fetch = +refs/heads/*:refs/remotes/staging/* | |
d5cd5de4 BF |
467 | ... |
468 | ------------------------------------------------- | |
469 | ||
2de9b711 | 470 | This is what causes Git to track the remote's branches; you may modify |
1249d8ad | 471 | or delete these configuration options by editing `.git/config` with a |
fc90c536 | 472 | text editor. (See the "CONFIGURATION FILE" section of |
5162e697 | 473 | linkgit:git-config[1] for details.) |
d5cd5de4 | 474 | |
e34caace | 475 | [[exploring-git-history]] |
2de9b711 | 476 | Exploring Git history |
d19fbc3c BF |
477 | ===================== |
478 | ||
479 | Git is best thought of as a tool for storing the history of a | |
480 | collection of files. It does this by storing compressed snapshots of | |
1130845b | 481 | the contents of a file hierarchy, together with "commits" which show |
d19fbc3c BF |
482 | the relationships between these snapshots. |
483 | ||
484 | Git provides extremely flexible and fast tools for exploring the | |
485 | history of a project. | |
486 | ||
aacd404e | 487 | We start with one specialized tool that is useful for finding the |
d19fbc3c BF |
488 | commit that introduced a bug into a project. |
489 | ||
e34caace | 490 | [[using-bisect]] |
d19fbc3c BF |
491 | How to use bisect to find a regression |
492 | -------------------------------------- | |
493 | ||
494 | Suppose version 2.6.18 of your project worked, but the version at | |
495 | "master" crashes. Sometimes the best way to find the cause of such a | |
496 | regression is to perform a brute-force search through the project's | |
497 | history to find the particular commit that caused the problem. The | |
5162e697 | 498 | linkgit:git-bisect[1] command can help you do this: |
d19fbc3c BF |
499 | |
500 | ------------------------------------------------- | |
501 | $ git bisect start | |
502 | $ git bisect good v2.6.18 | |
503 | $ git bisect bad master | |
504 | Bisecting: 3537 revisions left to test after this | |
505 | [65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6] | |
506 | ------------------------------------------------- | |
507 | ||
1249d8ad | 508 | If you run `git branch` at this point, you'll see that Git has |
0e25790f CC |
509 | temporarily moved you in "(no branch)". HEAD is now detached from any |
510 | branch and points directly to a commit (with commit id 65934...) that | |
511 | is reachable from "master" but not from v2.6.18. Compile and test it, | |
512 | and see whether it crashes. Assume it does crash. Then: | |
d19fbc3c BF |
513 | |
514 | ------------------------------------------------- | |
515 | $ git bisect bad | |
516 | Bisecting: 1769 revisions left to test after this | |
517 | [7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings | |
518 | ------------------------------------------------- | |
519 | ||
2de9b711 | 520 | checks out an older version. Continue like this, telling Git at each |
d19fbc3c BF |
521 | stage whether the version it gives you is good or bad, and notice |
522 | that the number of revisions left to test is cut approximately in | |
523 | half each time. | |
524 | ||
525 | After about 13 tests (in this case), it will output the commit id of | |
526 | the guilty commit. You can then examine the commit with | |
5162e697 | 527 | linkgit:git-show[1], find out who wrote it, and mail them your bug |
d19fbc3c BF |
528 | report with the commit id. Finally, run |
529 | ||
530 | ------------------------------------------------- | |
531 | $ git bisect reset | |
532 | ------------------------------------------------- | |
533 | ||
0e25790f | 534 | to return you to the branch you were on before. |
d19fbc3c | 535 | |
6127c086 | 536 | Note that the version which `git bisect` checks out for you at each |
d19fbc3c BF |
537 | point is just a suggestion, and you're free to try a different |
538 | version if you think it would be a good idea. For example, | |
539 | occasionally you may land on a commit that broke something unrelated; | |
540 | run | |
541 | ||
542 | ------------------------------------------------- | |
04483524 | 543 | $ git bisect visualize |
d19fbc3c BF |
544 | ------------------------------------------------- |
545 | ||
546 | which will run gitk and label the commit it chose with a marker that | |
843c81dc | 547 | says "bisect". Choose a safe-looking commit nearby, note its commit |
d19fbc3c BF |
548 | id, and check it out with: |
549 | ||
550 | ------------------------------------------------- | |
551 | $ git reset --hard fb47ddb2db... | |
552 | ------------------------------------------------- | |
553 | ||
1249d8ad | 554 | then test, run `bisect good` or `bisect bad` as appropriate, and |
d19fbc3c BF |
555 | continue. |
556 | ||
1249d8ad TK |
557 | Instead of `git bisect visualize` and then `git reset --hard |
558 | fb47ddb2db...`, you might just want to tell Git that you want to skip | |
0e25790f CC |
559 | the current commit: |
560 | ||
561 | ------------------------------------------------- | |
562 | $ git bisect skip | |
563 | ------------------------------------------------- | |
564 | ||
2de9b711 | 565 | In this case, though, Git may not eventually be able to tell the first |
a0178ae2 | 566 | bad one between some first skipped commits and a later bad commit. |
0e25790f CC |
567 | |
568 | There are also ways to automate the bisecting process if you have a | |
569 | test script that can tell a good from a bad commit. See | |
1249d8ad TK |
570 | linkgit:git-bisect[1] for more information about this and other `git |
571 | bisect` features. | |
0e25790f | 572 | |
e34caace | 573 | [[naming-commits]] |
d19fbc3c BF |
574 | Naming commits |
575 | -------------- | |
576 | ||
577 | We have seen several ways of naming commits already: | |
578 | ||
d55ae921 | 579 | - 40-hexdigit object name |
d19fbc3c BF |
580 | - branch name: refers to the commit at the head of the given |
581 | branch | |
582 | - tag name: refers to the commit pointed to by the given tag | |
583 | (we've seen branches and tags are special cases of | |
584 | <<how-git-stores-references,references>>). | |
585 | - HEAD: refers to the head of the current branch | |
586 | ||
eb6ae7f4 | 587 | There are many more; see the "SPECIFYING REVISIONS" section of the |
9d83e382 | 588 | linkgit:gitrevisions[7] man page for the complete list of ways to |
d19fbc3c BF |
589 | name revisions. Some examples: |
590 | ||
591 | ------------------------------------------------- | |
d55ae921 | 592 | $ git show fb47ddb2 # the first few characters of the object name |
d19fbc3c BF |
593 | # are usually enough to specify it uniquely |
594 | $ git show HEAD^ # the parent of the HEAD commit | |
595 | $ git show HEAD^^ # the grandparent | |
596 | $ git show HEAD~4 # the great-great-grandparent | |
597 | ------------------------------------------------- | |
598 | ||
599 | Recall that merge commits may have more than one parent; by default, | |
1249d8ad | 600 | `^` and `~` follow the first parent listed in the commit, but you can |
d19fbc3c BF |
601 | also choose: |
602 | ||
603 | ------------------------------------------------- | |
604 | $ git show HEAD^1 # show the first parent of HEAD | |
605 | $ git show HEAD^2 # show the second parent of HEAD | |
606 | ------------------------------------------------- | |
607 | ||
608 | In addition to HEAD, there are several other special names for | |
609 | commits: | |
610 | ||
611 | Merges (to be discussed later), as well as operations such as | |
6127c086 | 612 | `git reset`, which change the currently checked-out commit, generally |
d19fbc3c BF |
613 | set ORIG_HEAD to the value HEAD had before the current operation. |
614 | ||
6127c086 FC |
615 | The `git fetch` operation always stores the head of the last fetched |
616 | branch in FETCH_HEAD. For example, if you run `git fetch` without | |
d19fbc3c BF |
617 | specifying a local branch as the target of the operation |
618 | ||
619 | ------------------------------------------------- | |
620 | $ git fetch git://example.com/proj.git theirbranch | |
621 | ------------------------------------------------- | |
622 | ||
623 | the fetched commits will still be available from FETCH_HEAD. | |
624 | ||
625 | When we discuss merges we'll also see the special name MERGE_HEAD, | |
626 | which refers to the other branch that we're merging in to the current | |
627 | branch. | |
628 | ||
5162e697 | 629 | The linkgit:git-rev-parse[1] command is a low-level command that is |
d55ae921 BF |
630 | occasionally useful for translating some name for a commit to the object |
631 | name for that commit: | |
aec053bb BF |
632 | |
633 | ------------------------------------------------- | |
634 | $ git rev-parse origin | |
635 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
636 | ------------------------------------------------- | |
637 | ||
e34caace | 638 | [[creating-tags]] |
d19fbc3c BF |
639 | Creating tags |
640 | ------------- | |
641 | ||
642 | We can also create a tag to refer to a particular commit; after | |
643 | running | |
644 | ||
645 | ------------------------------------------------- | |
04483524 | 646 | $ git tag stable-1 1b2e1d63ff |
d19fbc3c BF |
647 | ------------------------------------------------- |
648 | ||
1249d8ad | 649 | You can use `stable-1` to refer to the commit 1b2e1d63ff. |
d19fbc3c | 650 | |
c64415e2 BF |
651 | This creates a "lightweight" tag. If you would also like to include a |
652 | comment with the tag, and possibly sign it cryptographically, then you | |
5162e697 | 653 | should create a tag object instead; see the linkgit:git-tag[1] man page |
c64415e2 | 654 | for details. |
d19fbc3c | 655 | |
e34caace | 656 | [[browsing-revisions]] |
d19fbc3c BF |
657 | Browsing revisions |
658 | ------------------ | |
659 | ||
5162e697 | 660 | The linkgit:git-log[1] command can show lists of commits. On its |
d19fbc3c BF |
661 | own, it shows all commits reachable from the parent commit; but you |
662 | can also make more specific requests: | |
663 | ||
664 | ------------------------------------------------- | |
665 | $ git log v2.5.. # commits since (not reachable from) v2.5 | |
666 | $ git log test..master # commits reachable from master but not test | |
667 | $ git log master..test # ...reachable from test but not master | |
668 | $ git log master...test # ...reachable from either test or master, | |
669 | # but not both | |
670 | $ git log --since="2 weeks ago" # commits from the last 2 weeks | |
671 | $ git log Makefile # commits which modify Makefile | |
672 | $ git log fs/ # ... which modify any file under fs/ | |
673 | $ git log -S'foo()' # commits which add or remove any file data | |
674 | # matching the string 'foo()' | |
675 | ------------------------------------------------- | |
676 | ||
677 | And of course you can combine all of these; the following finds | |
1249d8ad | 678 | commits since v2.5 which touch the `Makefile` or any file under `fs`: |
d19fbc3c BF |
679 | |
680 | ------------------------------------------------- | |
681 | $ git log v2.5.. Makefile fs/ | |
682 | ------------------------------------------------- | |
683 | ||
684 | You can also ask git log to show patches: | |
685 | ||
686 | ------------------------------------------------- | |
687 | $ git log -p | |
688 | ------------------------------------------------- | |
689 | ||
1249d8ad | 690 | See the `--pretty` option in the linkgit:git-log[1] man page for more |
d19fbc3c BF |
691 | display options. |
692 | ||
693 | Note that git log starts with the most recent commit and works | |
2de9b711 | 694 | backwards through the parents; however, since Git history can contain |
3dff5379 | 695 | multiple independent lines of development, the particular order that |
d19fbc3c BF |
696 | commits are listed in may be somewhat arbitrary. |
697 | ||
e34caace | 698 | [[generating-diffs]] |
d19fbc3c BF |
699 | Generating diffs |
700 | ---------------- | |
701 | ||
702 | You can generate diffs between any two versions using | |
5162e697 | 703 | linkgit:git-diff[1]: |
d19fbc3c BF |
704 | |
705 | ------------------------------------------------- | |
706 | $ git diff master..test | |
707 | ------------------------------------------------- | |
708 | ||
5b98d9bc BF |
709 | That will produce the diff between the tips of the two branches. If |
710 | you'd prefer to find the diff from their common ancestor to test, you | |
711 | can use three dots instead of two: | |
712 | ||
713 | ------------------------------------------------- | |
714 | $ git diff master...test | |
715 | ------------------------------------------------- | |
716 | ||
717 | Sometimes what you want instead is a set of patches; for this you can | |
5162e697 | 718 | use linkgit:git-format-patch[1]: |
d19fbc3c BF |
719 | |
720 | ------------------------------------------------- | |
721 | $ git format-patch master..test | |
722 | ------------------------------------------------- | |
723 | ||
724 | will generate a file with a patch for each commit reachable from test | |
5b98d9bc | 725 | but not from master. |
d19fbc3c | 726 | |
e34caace | 727 | [[viewing-old-file-versions]] |
d19fbc3c BF |
728 | Viewing old file versions |
729 | ------------------------- | |
730 | ||
731 | You can always view an old version of a file by just checking out the | |
732 | correct revision first. But sometimes it is more convenient to be | |
733 | able to view an old version of a single file without checking | |
734 | anything out; this command does that: | |
735 | ||
736 | ------------------------------------------------- | |
737 | $ git show v2.5:fs/locks.c | |
738 | ------------------------------------------------- | |
739 | ||
740 | Before the colon may be anything that names a commit, and after it | |
2de9b711 | 741 | may be any path to a file tracked by Git. |
d19fbc3c | 742 | |
e34caace | 743 | [[history-examples]] |
aec053bb BF |
744 | Examples |
745 | -------- | |
746 | ||
46acd3fa BF |
747 | [[counting-commits-on-a-branch]] |
748 | Counting the number of commits on a branch | |
749 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
750 | ||
1249d8ad TK |
751 | Suppose you want to know how many commits you've made on `mybranch` |
752 | since it diverged from `origin`: | |
46acd3fa BF |
753 | |
754 | ------------------------------------------------- | |
755 | $ git log --pretty=oneline origin..mybranch | wc -l | |
756 | ------------------------------------------------- | |
757 | ||
758 | Alternatively, you may often see this sort of thing done with the | |
a6e5ef7d | 759 | lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's |
46acd3fa BF |
760 | of all the given commits: |
761 | ||
762 | ------------------------------------------------- | |
763 | $ git rev-list origin..mybranch | wc -l | |
764 | ------------------------------------------------- | |
765 | ||
e34caace | 766 | [[checking-for-equal-branches]] |
aec053bb | 767 | Check whether two branches point at the same history |
2f99710c | 768 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
aec053bb BF |
769 | |
770 | Suppose you want to check whether two branches point at the same point | |
771 | in history. | |
772 | ||
773 | ------------------------------------------------- | |
774 | $ git diff origin..master | |
775 | ------------------------------------------------- | |
776 | ||
69f7ad73 BF |
777 | will tell you whether the contents of the project are the same at the |
778 | two branches; in theory, however, it's possible that the same project | |
779 | contents could have been arrived at by two different historical | |
d55ae921 | 780 | routes. You could compare the object names: |
aec053bb BF |
781 | |
782 | ------------------------------------------------- | |
783 | $ git rev-list origin | |
784 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
785 | $ git rev-list master | |
786 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
787 | ------------------------------------------------- | |
788 | ||
1249d8ad | 789 | Or you could recall that the `...` operator selects all commits |
69f7ad73 | 790 | contained reachable from either one reference or the other but not |
ddd2369c | 791 | both; so |
aec053bb BF |
792 | |
793 | ------------------------------------------------- | |
794 | $ git log origin...master | |
795 | ------------------------------------------------- | |
796 | ||
797 | will return no commits when the two branches are equal. | |
798 | ||
e34caace | 799 | [[finding-tagged-descendants]] |
b181d57f BF |
800 | Find first tagged version including a given fix |
801 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
aec053bb | 802 | |
69f7ad73 BF |
803 | Suppose you know that the commit e05db0fd fixed a certain problem. |
804 | You'd like to find the earliest tagged release that contains that | |
805 | fix. | |
806 | ||
807 | Of course, there may be more than one answer--if the history branched | |
808 | after commit e05db0fd, then there could be multiple "earliest" tagged | |
809 | releases. | |
810 | ||
811 | You could just visually inspect the commits since e05db0fd: | |
812 | ||
813 | ------------------------------------------------- | |
814 | $ gitk e05db0fd.. | |
815 | ------------------------------------------------- | |
816 | ||
5162e697 | 817 | Or you can use linkgit:git-name-rev[1], which will give the commit a |
b181d57f BF |
818 | name based on any tag it finds pointing to one of the commit's |
819 | descendants: | |
820 | ||
821 | ------------------------------------------------- | |
04483524 | 822 | $ git name-rev --tags e05db0fd |
b181d57f BF |
823 | e05db0fd tags/v1.5.0-rc1^0~23 |
824 | ------------------------------------------------- | |
825 | ||
5162e697 | 826 | The linkgit:git-describe[1] command does the opposite, naming the |
b181d57f BF |
827 | revision using a tag on which the given commit is based: |
828 | ||
829 | ------------------------------------------------- | |
830 | $ git describe e05db0fd | |
04483524 | 831 | v1.5.0-rc0-260-ge05db0f |
b181d57f BF |
832 | ------------------------------------------------- |
833 | ||
834 | but that may sometimes help you guess which tags might come after the | |
835 | given commit. | |
836 | ||
837 | If you just want to verify whether a given tagged version contains a | |
5162e697 | 838 | given commit, you could use linkgit:git-merge-base[1]: |
b181d57f BF |
839 | |
840 | ------------------------------------------------- | |
841 | $ git merge-base e05db0fd v1.5.0-rc1 | |
842 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
843 | ------------------------------------------------- | |
844 | ||
845 | The merge-base command finds a common ancestor of the given commits, | |
846 | and always returns one or the other in the case where one is a | |
847 | descendant of the other; so the above output shows that e05db0fd | |
848 | actually is an ancestor of v1.5.0-rc1. | |
849 | ||
850 | Alternatively, note that | |
851 | ||
852 | ------------------------------------------------- | |
4a7979ca | 853 | $ git log v1.5.0-rc1..e05db0fd |
b181d57f BF |
854 | ------------------------------------------------- |
855 | ||
4a7979ca | 856 | will produce empty output if and only if v1.5.0-rc1 includes e05db0fd, |
b181d57f | 857 | because it outputs only commits that are not reachable from v1.5.0-rc1. |
aec053bb | 858 | |
5162e697 | 859 | As yet another alternative, the linkgit:git-show-branch[1] command lists |
4a7979ca BF |
860 | the commits reachable from its arguments with a display on the left-hand |
861 | side that indicates which arguments that commit is reachable from. So, | |
862 | you can run something like | |
863 | ||
864 | ------------------------------------------------- | |
865 | $ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2 | |
866 | ! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
867 | available | |
868 | ! [v1.5.0-rc0] GIT v1.5.0 preview | |
869 | ! [v1.5.0-rc1] GIT v1.5.0-rc1 | |
870 | ! [v1.5.0-rc2] GIT v1.5.0-rc2 | |
871 | ... | |
872 | ------------------------------------------------- | |
873 | ||
874 | then search for a line that looks like | |
875 | ||
876 | ------------------------------------------------- | |
877 | + ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
878 | available | |
879 | ------------------------------------------------- | |
880 | ||
881 | Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and | |
882 | from v1.5.0-rc2, but not from v1.5.0-rc0. | |
883 | ||
629d9f78 BF |
884 | [[showing-commits-unique-to-a-branch]] |
885 | Showing commits unique to a given branch | |
886 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
4a7979ca | 887 | |
629d9f78 | 888 | Suppose you would like to see all the commits reachable from the branch |
1249d8ad | 889 | head named `master` but not from any other head in your repository. |
d19fbc3c | 890 | |
629d9f78 | 891 | We can list all the heads in this repository with |
5162e697 | 892 | linkgit:git-show-ref[1]: |
d19fbc3c | 893 | |
629d9f78 BF |
894 | ------------------------------------------------- |
895 | $ git show-ref --heads | |
896 | bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial | |
897 | db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint | |
898 | a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master | |
899 | 24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2 | |
900 | 1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes | |
901 | ------------------------------------------------- | |
d19fbc3c | 902 | |
1249d8ad | 903 | We can get just the branch-head names, and remove `master`, with |
629d9f78 BF |
904 | the help of the standard utilities cut and grep: |
905 | ||
906 | ------------------------------------------------- | |
907 | $ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master' | |
908 | refs/heads/core-tutorial | |
909 | refs/heads/maint | |
910 | refs/heads/tutorial-2 | |
911 | refs/heads/tutorial-fixes | |
912 | ------------------------------------------------- | |
913 | ||
914 | And then we can ask to see all the commits reachable from master | |
915 | but not from these other heads: | |
916 | ||
917 | ------------------------------------------------- | |
918 | $ gitk master --not $( git show-ref --heads | cut -d' ' -f2 | | |
919 | grep -v '^refs/heads/master' ) | |
920 | ------------------------------------------------- | |
921 | ||
922 | Obviously, endless variations are possible; for example, to see all | |
923 | commits reachable from some head but not from any tag in the repository: | |
924 | ||
925 | ------------------------------------------------- | |
c78974f7 | 926 | $ gitk $( git show-ref --heads ) --not $( git show-ref --tags ) |
629d9f78 BF |
927 | ------------------------------------------------- |
928 | ||
9d83e382 | 929 | (See linkgit:gitrevisions[7] for explanations of commit-selecting |
629d9f78 BF |
930 | syntax such as `--not`.) |
931 | ||
82c8bf28 BF |
932 | [[making-a-release]] |
933 | Creating a changelog and tarball for a software release | |
934 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
935 | ||
5162e697 | 936 | The linkgit:git-archive[1] command can create a tar or zip archive from |
82c8bf28 BF |
937 | any version of a project; for example: |
938 | ||
939 | ------------------------------------------------- | |
7ed1690c | 940 | $ git archive -o latest.tar.gz --prefix=project/ HEAD |
82c8bf28 BF |
941 | ------------------------------------------------- |
942 | ||
7ed1690c TK |
943 | will use HEAD to produce a gzipped tar archive in which each filename |
944 | is preceded by `project/`. The output file format is inferred from | |
945 | the output file extension if possible, see linkgit:git-archive[1] for | |
946 | details. | |
947 | ||
1249d8ad | 948 | Versions of Git older than 1.7.7 don't know about the `tar.gz` format, |
7ed1690c TK |
949 | you'll need to use gzip explicitly: |
950 | ||
951 | ------------------------------------------------- | |
952 | $ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz | |
953 | ------------------------------------------------- | |
82c8bf28 BF |
954 | |
955 | If you're releasing a new version of a software project, you may want | |
956 | to simultaneously make a changelog to include in the release | |
957 | announcement. | |
958 | ||
959 | Linus Torvalds, for example, makes new kernel releases by tagging them, | |
960 | then running: | |
961 | ||
962 | ------------------------------------------------- | |
963 | $ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7 | |
964 | ------------------------------------------------- | |
965 | ||
966 | where release-script is a shell script that looks like: | |
967 | ||
968 | ------------------------------------------------- | |
969 | #!/bin/sh | |
970 | stable="$1" | |
971 | last="$2" | |
972 | new="$3" | |
973 | echo "# git tag v$new" | |
974 | echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz" | |
975 | echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz" | |
976 | echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new" | |
977 | echo "git shortlog --no-merges v$new ^v$last > ../ShortLog" | |
978 | echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new" | |
979 | ------------------------------------------------- | |
980 | ||
981 | and then he just cut-and-pastes the output commands after verifying that | |
982 | they look OK. | |
4a7979ca | 983 | |
e1ba4c32 | 984 | [[Finding-commits-With-given-Content]] |
187b0d80 | 985 | Finding commits referencing a file with given content |
d5821de2 | 986 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
187b0d80 BF |
987 | |
988 | Somebody hands you a copy of a file, and asks which commits modified a | |
989 | file such that it contained the given content either before or after the | |
990 | commit. You can find out with this: | |
991 | ||
992 | ------------------------------------------------- | |
477ff5b7 | 993 | $ git log --raw --abbrev=40 --pretty=oneline | |
187b0d80 BF |
994 | grep -B 1 `git hash-object filename` |
995 | ------------------------------------------------- | |
996 | ||
997 | Figuring out why this works is left as an exercise to the (advanced) | |
5162e697 DM |
998 | student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and |
999 | linkgit:git-hash-object[1] man pages may prove helpful. | |
187b0d80 | 1000 | |
aa971cb9 | 1001 | [[Developing-With-git]] |
2de9b711 | 1002 | Developing with Git |
d19fbc3c BF |
1003 | =================== |
1004 | ||
e34caace | 1005 | [[telling-git-your-name]] |
2de9b711 | 1006 | Telling Git your name |
d19fbc3c BF |
1007 | --------------------- |
1008 | ||
632cc3e6 TK |
1009 | Before creating any commits, you should introduce yourself to Git. |
1010 | The easiest way to do so is to use linkgit:git-config[1]: | |
1011 | ||
1012 | ------------------------------------------------ | |
1013 | $ git config --global user.name 'Your Name Comes Here' | |
1014 | $ git config --global user.email 'you@yourdomain.example.com' | |
1015 | ------------------------------------------------ | |
1016 | ||
1017 | Which will add the following to a file named `.gitconfig` in your | |
1018 | home directory: | |
d19fbc3c BF |
1019 | |
1020 | ------------------------------------------------ | |
d19fbc3c BF |
1021 | [user] |
1022 | name = Your Name Comes Here | |
1023 | email = you@yourdomain.example.com | |
d19fbc3c BF |
1024 | ------------------------------------------------ |
1025 | ||
632cc3e6 TK |
1026 | See the "CONFIGURATION FILE" section of linkgit:git-config[1] for |
1027 | details on the configuration file. The file is plain text, so you can | |
1028 | also edit it with your favorite editor. | |
fc90c536 | 1029 | |
d19fbc3c | 1030 | |
e34caace | 1031 | [[creating-a-new-repository]] |
d19fbc3c BF |
1032 | Creating a new repository |
1033 | ------------------------- | |
1034 | ||
1035 | Creating a new repository from scratch is very easy: | |
1036 | ||
1037 | ------------------------------------------------- | |
1038 | $ mkdir project | |
1039 | $ cd project | |
f1d2b477 | 1040 | $ git init |
d19fbc3c BF |
1041 | ------------------------------------------------- |
1042 | ||
1043 | If you have some initial content (say, a tarball): | |
1044 | ||
1045 | ------------------------------------------------- | |
0ddd93b2 | 1046 | $ tar xzvf project.tar.gz |
d19fbc3c | 1047 | $ cd project |
f1d2b477 | 1048 | $ git init |
d19fbc3c BF |
1049 | $ git add . # include everything below ./ in the first commit: |
1050 | $ git commit | |
1051 | ------------------------------------------------- | |
1052 | ||
1053 | [[how-to-make-a-commit]] | |
ae25c67a | 1054 | How to make a commit |
d19fbc3c BF |
1055 | -------------------- |
1056 | ||
1057 | Creating a new commit takes three steps: | |
1058 | ||
1059 | 1. Making some changes to the working directory using your | |
1060 | favorite editor. | |
2de9b711 TA |
1061 | 2. Telling Git about your changes. |
1062 | 3. Creating the commit using the content you told Git about | |
d19fbc3c BF |
1063 | in step 2. |
1064 | ||
1065 | In practice, you can interleave and repeat steps 1 and 2 as many | |
1066 | times as you want: in order to keep track of what you want committed | |
2de9b711 | 1067 | at step 3, Git maintains a snapshot of the tree's contents in a |
d19fbc3c BF |
1068 | special staging area called "the index." |
1069 | ||
01997b4a | 1070 | At the beginning, the content of the index will be identical to |
1249d8ad | 1071 | that of the HEAD. The command `git diff --cached`, which shows |
01997b4a BF |
1072 | the difference between the HEAD and the index, should therefore |
1073 | produce no output at that point. | |
eb6ae7f4 | 1074 | |
d19fbc3c BF |
1075 | Modifying the index is easy: |
1076 | ||
1077 | To update the index with the new contents of a modified file, use | |
1078 | ||
1079 | ------------------------------------------------- | |
1080 | $ git add path/to/file | |
1081 | ------------------------------------------------- | |
1082 | ||
1083 | To add the contents of a new file to the index, use | |
1084 | ||
1085 | ------------------------------------------------- | |
1086 | $ git add path/to/file | |
1087 | ------------------------------------------------- | |
1088 | ||
eb6ae7f4 | 1089 | To remove a file from the index and from the working tree, |
d19fbc3c BF |
1090 | |
1091 | ------------------------------------------------- | |
1092 | $ git rm path/to/file | |
1093 | ------------------------------------------------- | |
1094 | ||
1095 | After each step you can verify that | |
1096 | ||
1097 | ------------------------------------------------- | |
1098 | $ git diff --cached | |
1099 | ------------------------------------------------- | |
1100 | ||
1101 | always shows the difference between the HEAD and the index file--this | |
1102 | is what you'd commit if you created the commit now--and that | |
1103 | ||
1104 | ------------------------------------------------- | |
1105 | $ git diff | |
1106 | ------------------------------------------------- | |
1107 | ||
1108 | shows the difference between the working tree and the index file. | |
1109 | ||
1249d8ad | 1110 | Note that `git add` always adds just the current contents of a file |
d19fbc3c | 1111 | to the index; further changes to the same file will be ignored unless |
6127c086 | 1112 | you run `git add` on the file again. |
d19fbc3c BF |
1113 | |
1114 | When you're ready, just run | |
1115 | ||
1116 | ------------------------------------------------- | |
1117 | $ git commit | |
1118 | ------------------------------------------------- | |
1119 | ||
2de9b711 | 1120 | and Git will prompt you for a commit message and then create the new |
3dff5379 | 1121 | commit. Check to make sure it looks like what you expected with |
d19fbc3c BF |
1122 | |
1123 | ------------------------------------------------- | |
1124 | $ git show | |
1125 | ------------------------------------------------- | |
1126 | ||
1127 | As a special shortcut, | |
a6080a0a | 1128 | |
d19fbc3c BF |
1129 | ------------------------------------------------- |
1130 | $ git commit -a | |
1131 | ------------------------------------------------- | |
1132 | ||
1133 | will update the index with any files that you've modified or removed | |
1134 | and create a commit, all in one step. | |
1135 | ||
1136 | A number of commands are useful for keeping track of what you're | |
1137 | about to commit: | |
1138 | ||
1139 | ------------------------------------------------- | |
1140 | $ git diff --cached # difference between HEAD and the index; what | |
1130845b | 1141 | # would be committed if you ran "commit" now. |
d19fbc3c BF |
1142 | $ git diff # difference between the index file and your |
1143 | # working directory; changes that would not | |
1144 | # be included if you ran "commit" now. | |
c64415e2 BF |
1145 | $ git diff HEAD # difference between HEAD and working tree; what |
1146 | # would be committed if you ran "commit -a" now. | |
d19fbc3c BF |
1147 | $ git status # a brief per-file summary of the above. |
1148 | ------------------------------------------------- | |
1149 | ||
5162e697 | 1150 | You can also use linkgit:git-gui[1] to create commits, view changes in |
407c0c87 BF |
1151 | the index and the working tree files, and individually select diff hunks |
1152 | for inclusion in the index (by right-clicking on the diff hunk and | |
1153 | choosing "Stage Hunk For Commit"). | |
1154 | ||
e34caace | 1155 | [[creating-good-commit-messages]] |
ae25c67a | 1156 | Creating good commit messages |
d19fbc3c BF |
1157 | ----------------------------- |
1158 | ||
1159 | Though not required, it's a good idea to begin the commit message | |
1160 | with a single short (less than 50 character) line summarizing the | |
1161 | change, followed by a blank line and then a more thorough | |
52ffe995 JW |
1162 | description. The text up to the first blank line in a commit |
1163 | message is treated as the commit title, and that title is used | |
2de9b711 | 1164 | throughout Git. For example, linkgit:git-format-patch[1] turns a |
52ffe995 JW |
1165 | commit into email, and it uses the title on the Subject line and the |
1166 | rest of the commit in the body. | |
1167 | ||
d19fbc3c | 1168 | |
2dc53617 JH |
1169 | [[ignoring-files]] |
1170 | Ignoring files | |
1171 | -------------- | |
1172 | ||
2de9b711 | 1173 | A project will often generate files that you do 'not' want to track with Git. |
2dc53617 | 1174 | This typically includes files generated by a build process or temporary |
2de9b711 | 1175 | backup files made by your editor. Of course, 'not' tracking files with Git |
6127c086 | 1176 | is just a matter of 'not' calling `git add` on them. But it quickly becomes |
2dc53617 | 1177 | annoying to have these untracked files lying around; e.g. they make |
dcb11263 CJ |
1178 | `git add .` practically useless, and they keep showing up in the output of |
1179 | `git status`. | |
2dc53617 | 1180 | |
1249d8ad TK |
1181 | You can tell Git to ignore certain files by creating a file called |
1182 | `.gitignore` in the top level of your working directory, with contents | |
1183 | such as: | |
2dc53617 JH |
1184 | |
1185 | ------------------------------------------------- | |
1186 | # Lines starting with '#' are considered comments. | |
464a8a7a | 1187 | # Ignore any file named foo.txt. |
2dc53617 JH |
1188 | foo.txt |
1189 | # Ignore (generated) html files, | |
1190 | *.html | |
1191 | # except foo.html which is maintained by hand. | |
1192 | !foo.html | |
1193 | # Ignore objects and archives. | |
1194 | *.[oa] | |
1195 | ------------------------------------------------- | |
1196 | ||
5162e697 | 1197 | See linkgit:gitignore[5] for a detailed explanation of the syntax. You can |
464a8a7a BF |
1198 | also place .gitignore files in other directories in your working tree, and they |
1199 | will apply to those directories and their subdirectories. The `.gitignore` | |
1200 | files can be added to your repository like any other files (just run `git add | |
1201 | .gitignore` and `git commit`, as usual), which is convenient when the exclude | |
1202 | patterns (such as patterns matching build output files) would also make sense | |
1203 | for other users who clone your repository. | |
1204 | ||
1205 | If you wish the exclude patterns to affect only certain repositories | |
1206 | (instead of every repository for a given project), you may instead put | |
1249d8ad TK |
1207 | them in a file in your repository named `.git/info/exclude`, or in any |
1208 | file specified by the `core.excludesfile` configuration variable. | |
1209 | Some Git commands can also take exclude patterns directly on the | |
1210 | command line. See linkgit:gitignore[5] for the details. | |
2dc53617 | 1211 | |
e34caace | 1212 | [[how-to-merge]] |
ae25c67a | 1213 | How to merge |
d19fbc3c BF |
1214 | ------------ |
1215 | ||
1216 | You can rejoin two diverging branches of development using | |
5162e697 | 1217 | linkgit:git-merge[1]: |
d19fbc3c BF |
1218 | |
1219 | ------------------------------------------------- | |
1220 | $ git merge branchname | |
1221 | ------------------------------------------------- | |
1222 | ||
1249d8ad | 1223 | merges the development in the branch `branchname` into the current |
e63ec003 MM |
1224 | branch. |
1225 | ||
1249d8ad | 1226 | A merge is made by combining the changes made in `branchname` and the |
e63ec003 MM |
1227 | changes made up to the latest commit in your current branch since |
1228 | their histories forked. The work tree is overwritten by the result of | |
1229 | the merge when this combining is done cleanly, or overwritten by a | |
1230 | half-merged results when this combining results in conflicts. | |
1231 | Therefore, if you have uncommitted changes touching the same files as | |
1232 | the ones impacted by the merge, Git will refuse to proceed. Most of | |
1233 | the time, you will want to commit your changes before you can merge, | |
1234 | and if you don't, then linkgit:git-stash[1] can take these changes | |
1235 | away while you're doing the merge, and reapply them afterwards. | |
1236 | ||
6a5d0b0a | 1237 | If the changes are independent enough, Git will automatically complete |
e63ec003 MM |
1238 | the merge and commit the result (or reuse an existing commit in case |
1239 | of <<fast-forwards,fast-forward>>, see below). On the other hand, | |
1240 | if there are conflicts--for example, if the same file is | |
d19fbc3c BF |
1241 | modified in two different ways in the remote branch and the local |
1242 | branch--then you are warned; the output may look something like this: | |
1243 | ||
1244 | ------------------------------------------------- | |
fabbd8f6 BF |
1245 | $ git merge next |
1246 | 100% (4/4) done | |
1247 | Auto-merged file.txt | |
d19fbc3c BF |
1248 | CONFLICT (content): Merge conflict in file.txt |
1249 | Automatic merge failed; fix conflicts and then commit the result. | |
1250 | ------------------------------------------------- | |
1251 | ||
1252 | Conflict markers are left in the problematic files, and after | |
1253 | you resolve the conflicts manually, you can update the index | |
2de9b711 | 1254 | with the contents and run Git commit, as you normally would when |
d19fbc3c BF |
1255 | creating a new file. |
1256 | ||
1257 | If you examine the resulting commit using gitk, you will see that it | |
1258 | has two parents, one pointing to the top of the current branch, and | |
1259 | one to the top of the other branch. | |
1260 | ||
d19fbc3c BF |
1261 | [[resolving-a-merge]] |
1262 | Resolving a merge | |
1263 | ----------------- | |
1264 | ||
2de9b711 | 1265 | When a merge isn't resolved automatically, Git leaves the index and |
d19fbc3c BF |
1266 | the working tree in a special state that gives you all the |
1267 | information you need to help resolve the merge. | |
1268 | ||
1269 | Files with conflicts are marked specially in the index, so until you | |
5162e697 | 1270 | resolve the problem and update the index, linkgit:git-commit[1] will |
ef561ac7 | 1271 | fail: |
d19fbc3c BF |
1272 | |
1273 | ------------------------------------------------- | |
1274 | $ git commit | |
1275 | file.txt: needs merge | |
1276 | ------------------------------------------------- | |
1277 | ||
5162e697 | 1278 | Also, linkgit:git-status[1] will list those files as "unmerged", and the |
ef561ac7 BF |
1279 | files with conflicts will have conflict markers added, like this: |
1280 | ||
1281 | ------------------------------------------------- | |
1282 | <<<<<<< HEAD:file.txt | |
1283 | Hello world | |
1284 | ======= | |
1285 | Goodbye | |
1286 | >>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1287 | ------------------------------------------------- | |
1288 | ||
1289 | All you need to do is edit the files to resolve the conflicts, and then | |
1290 | ||
1291 | ------------------------------------------------- | |
1292 | $ git add file.txt | |
1293 | $ git commit | |
1294 | ------------------------------------------------- | |
1295 | ||
1296 | Note that the commit message will already be filled in for you with | |
1297 | some information about the merge. Normally you can just use this | |
1298 | default message unchanged, but you may add additional commentary of | |
1299 | your own if desired. | |
1300 | ||
2de9b711 | 1301 | The above is all you need to know to resolve a simple merge. But Git |
ef561ac7 BF |
1302 | also provides more information to help resolve conflicts: |
1303 | ||
e34caace | 1304 | [[conflict-resolution]] |
ef561ac7 BF |
1305 | Getting conflict-resolution help during a merge |
1306 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 1307 | |
2de9b711 | 1308 | All of the changes that Git was able to merge automatically are |
5162e697 | 1309 | already added to the index file, so linkgit:git-diff[1] shows only |
ef561ac7 | 1310 | the conflicts. It uses an unusual syntax: |
d19fbc3c BF |
1311 | |
1312 | ------------------------------------------------- | |
1313 | $ git diff | |
1314 | diff --cc file.txt | |
1315 | index 802992c,2b60207..0000000 | |
1316 | --- a/file.txt | |
1317 | +++ b/file.txt | |
1318 | @@@ -1,1 -1,1 +1,5 @@@ | |
1319 | ++<<<<<<< HEAD:file.txt | |
1320 | +Hello world | |
1321 | ++======= | |
1322 | + Goodbye | |
1323 | ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1324 | ------------------------------------------------- | |
1325 | ||
1130845b | 1326 | Recall that the commit which will be committed after we resolve this |
d19fbc3c BF |
1327 | conflict will have two parents instead of the usual one: one parent |
1328 | will be HEAD, the tip of the current branch; the other will be the | |
1329 | tip of the other branch, which is stored temporarily in MERGE_HEAD. | |
1330 | ||
ef561ac7 BF |
1331 | During the merge, the index holds three versions of each file. Each of |
1332 | these three "file stages" represents a different version of the file: | |
1333 | ||
1334 | ------------------------------------------------- | |
1335 | $ git show :1:file.txt # the file in a common ancestor of both branches | |
4209752d JH |
1336 | $ git show :2:file.txt # the version from HEAD. |
1337 | $ git show :3:file.txt # the version from MERGE_HEAD. | |
ef561ac7 BF |
1338 | ------------------------------------------------- |
1339 | ||
4209752d JH |
1340 | When you ask linkgit:git-diff[1] to show the conflicts, it runs a |
1341 | three-way diff between the conflicted merge results in the work tree with | |
1342 | stages 2 and 3 to show only hunks whose contents come from both sides, | |
1343 | mixed (in other words, when a hunk's merge results come only from stage 2, | |
1344 | that part is not conflicting and is not shown. Same for stage 3). | |
ef561ac7 BF |
1345 | |
1346 | The diff above shows the differences between the working-tree version of | |
1347 | file.txt and the stage 2 and stage 3 versions. So instead of preceding | |
1249d8ad | 1348 | each line by a single `+` or `-`, it now uses two columns: the first |
ef561ac7 BF |
1349 | column is used for differences between the first parent and the working |
1350 | directory copy, and the second for differences between the second parent | |
1351 | and the working directory copy. (See the "COMBINED DIFF FORMAT" section | |
5162e697 | 1352 | of linkgit:git-diff-files[1] for a details of the format.) |
ef561ac7 BF |
1353 | |
1354 | After resolving the conflict in the obvious way (but before updating the | |
1355 | index), the diff will look like: | |
d19fbc3c BF |
1356 | |
1357 | ------------------------------------------------- | |
1358 | $ git diff | |
1359 | diff --cc file.txt | |
1360 | index 802992c,2b60207..0000000 | |
1361 | --- a/file.txt | |
1362 | +++ b/file.txt | |
1363 | @@@ -1,1 -1,1 +1,1 @@@ | |
1364 | - Hello world | |
1365 | -Goodbye | |
1366 | ++Goodbye world | |
1367 | ------------------------------------------------- | |
1368 | ||
1369 | This shows that our resolved version deleted "Hello world" from the | |
1370 | first parent, deleted "Goodbye" from the second parent, and added | |
1371 | "Goodbye world", which was previously absent from both. | |
1372 | ||
ef561ac7 BF |
1373 | Some special diff options allow diffing the working directory against |
1374 | any of these stages: | |
1375 | ||
1376 | ------------------------------------------------- | |
1377 | $ git diff -1 file.txt # diff against stage 1 | |
1378 | $ git diff --base file.txt # same as the above | |
1379 | $ git diff -2 file.txt # diff against stage 2 | |
1380 | $ git diff --ours file.txt # same as the above | |
1381 | $ git diff -3 file.txt # diff against stage 3 | |
1382 | $ git diff --theirs file.txt # same as the above. | |
1383 | ------------------------------------------------- | |
1384 | ||
0cafe944 | 1385 | The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help |
ef561ac7 | 1386 | for merges: |
d19fbc3c BF |
1387 | |
1388 | ------------------------------------------------- | |
1389 | $ git log --merge | |
ef561ac7 | 1390 | $ gitk --merge |
d19fbc3c BF |
1391 | ------------------------------------------------- |
1392 | ||
ef561ac7 BF |
1393 | These will display all commits which exist only on HEAD or on |
1394 | MERGE_HEAD, and which touch an unmerged file. | |
d19fbc3c | 1395 | |
5162e697 | 1396 | You may also use linkgit:git-mergetool[1], which lets you merge the |
c7719fbe | 1397 | unmerged files using external tools such as Emacs or kdiff3. |
c64415e2 | 1398 | |
ef561ac7 | 1399 | Each time you resolve the conflicts in a file and update the index: |
d19fbc3c BF |
1400 | |
1401 | ------------------------------------------------- | |
1402 | $ git add file.txt | |
d19fbc3c BF |
1403 | ------------------------------------------------- |
1404 | ||
ef561ac7 | 1405 | the different stages of that file will be "collapsed", after which |
6127c086 | 1406 | `git diff` will (by default) no longer show diffs for that file. |
d19fbc3c BF |
1407 | |
1408 | [[undoing-a-merge]] | |
ae25c67a | 1409 | Undoing a merge |
d19fbc3c BF |
1410 | --------------- |
1411 | ||
1412 | If you get stuck and decide to just give up and throw the whole mess | |
1413 | away, you can always return to the pre-merge state with | |
1414 | ||
1415 | ------------------------------------------------- | |
1416 | $ git reset --hard HEAD | |
1417 | ------------------------------------------------- | |
1418 | ||
1130845b | 1419 | Or, if you've already committed the merge that you want to throw away, |
d19fbc3c BF |
1420 | |
1421 | ------------------------------------------------- | |
1c73bb0e | 1422 | $ git reset --hard ORIG_HEAD |
d19fbc3c BF |
1423 | ------------------------------------------------- |
1424 | ||
1425 | However, this last command can be dangerous in some cases--never | |
1426 | throw away a commit you have already committed if that commit may | |
1427 | itself have been merged into another branch, as doing so may confuse | |
1428 | further merges. | |
1429 | ||
e34caace | 1430 | [[fast-forwards]] |
d19fbc3c BF |
1431 | Fast-forward merges |
1432 | ------------------- | |
1433 | ||
1434 | There is one special case not mentioned above, which is treated | |
1435 | differently. Normally, a merge results in a merge commit, with two | |
1436 | parents, one pointing at each of the two lines of development that | |
1437 | were merged. | |
1438 | ||
59723040 | 1439 | However, if the current branch is a descendant of the other--so every |
2de9b711 | 1440 | commit present in the one is already contained in the other--then Git |
a75d7b54 | 1441 | just performs a "fast-forward"; the head of the current branch is moved |
59723040 BF |
1442 | forward to point at the head of the merged-in branch, without any new |
1443 | commits being created. | |
d19fbc3c | 1444 | |
e34caace | 1445 | [[fixing-mistakes]] |
b684f830 BF |
1446 | Fixing mistakes |
1447 | --------------- | |
1448 | ||
1449 | If you've messed up the working tree, but haven't yet committed your | |
1450 | mistake, you can return the entire working tree to the last committed | |
1451 | state with | |
1452 | ||
1453 | ------------------------------------------------- | |
1454 | $ git reset --hard HEAD | |
1455 | ------------------------------------------------- | |
1456 | ||
1457 | If you make a commit that you later wish you hadn't, there are two | |
1458 | fundamentally different ways to fix the problem: | |
1459 | ||
1460 | 1. You can create a new commit that undoes whatever was done | |
93cbbd71 | 1461 | by the old commit. This is the correct thing if your |
b684f830 BF |
1462 | mistake has already been made public. |
1463 | ||
1464 | 2. You can go back and modify the old commit. You should | |
1465 | never do this if you have already made the history public; | |
2de9b711 | 1466 | Git does not normally expect the "history" of a project to |
b684f830 BF |
1467 | change, and cannot correctly perform repeated merges from |
1468 | a branch that has had its history changed. | |
1469 | ||
e34caace | 1470 | [[reverting-a-commit]] |
b684f830 BF |
1471 | Fixing a mistake with a new commit |
1472 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1473 | ||
1474 | Creating a new commit that reverts an earlier change is very easy; | |
5162e697 | 1475 | just pass the linkgit:git-revert[1] command a reference to the bad |
b684f830 BF |
1476 | commit; for example, to revert the most recent commit: |
1477 | ||
1478 | ------------------------------------------------- | |
1479 | $ git revert HEAD | |
1480 | ------------------------------------------------- | |
1481 | ||
1482 | This will create a new commit which undoes the change in HEAD. You | |
1483 | will be given a chance to edit the commit message for the new commit. | |
1484 | ||
1485 | You can also revert an earlier change, for example, the next-to-last: | |
1486 | ||
1487 | ------------------------------------------------- | |
1488 | $ git revert HEAD^ | |
1489 | ------------------------------------------------- | |
1490 | ||
2de9b711 | 1491 | In this case Git will attempt to undo the old change while leaving |
b684f830 BF |
1492 | intact any changes made since then. If more recent changes overlap |
1493 | with the changes to be reverted, then you will be asked to fix | |
1494 | conflicts manually, just as in the case of <<resolving-a-merge, | |
1495 | resolving a merge>>. | |
1496 | ||
7cb192ea BF |
1497 | [[fixing-a-mistake-by-rewriting-history]] |
1498 | Fixing a mistake by rewriting history | |
b684f830 BF |
1499 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
1500 | ||
1501 | If the problematic commit is the most recent commit, and you have not | |
1502 | yet made that commit public, then you may just | |
6127c086 | 1503 | <<undoing-a-merge,destroy it using `git reset`>>. |
b684f830 BF |
1504 | |
1505 | Alternatively, you | |
1506 | can edit the working directory and update the index to fix your | |
1507 | mistake, just as if you were going to <<how-to-make-a-commit,create a | |
1508 | new commit>>, then run | |
1509 | ||
1510 | ------------------------------------------------- | |
1511 | $ git commit --amend | |
1512 | ------------------------------------------------- | |
1513 | ||
1514 | which will replace the old commit by a new commit incorporating your | |
1515 | changes, giving you a chance to edit the old commit message first. | |
1516 | ||
1517 | Again, you should never do this to a commit that may already have | |
5162e697 | 1518 | been merged into another branch; use linkgit:git-revert[1] instead in |
b684f830 BF |
1519 | that case. |
1520 | ||
7cb192ea | 1521 | It is also possible to replace commits further back in the history, but |
b684f830 BF |
1522 | this is an advanced topic to be left for |
1523 | <<cleaning-up-history,another chapter>>. | |
1524 | ||
e34caace | 1525 | [[checkout-of-path]] |
b684f830 BF |
1526 | Checking out an old version of a file |
1527 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1528 | ||
1529 | In the process of undoing a previous bad change, you may find it | |
1530 | useful to check out an older version of a particular file using | |
6127c086 | 1531 | linkgit:git-checkout[1]. We've used `git checkout` before to switch |
b684f830 BF |
1532 | branches, but it has quite different behavior if it is given a path |
1533 | name: the command | |
1534 | ||
1535 | ------------------------------------------------- | |
1536 | $ git checkout HEAD^ path/to/file | |
1537 | ------------------------------------------------- | |
1538 | ||
1539 | replaces path/to/file by the contents it had in the commit HEAD^, and | |
1540 | also updates the index to match. It does not change branches. | |
1541 | ||
1542 | If you just want to look at an old version of the file, without | |
1543 | modifying the working directory, you can do that with | |
5162e697 | 1544 | linkgit:git-show[1]: |
b684f830 BF |
1545 | |
1546 | ------------------------------------------------- | |
ed4eb0d8 | 1547 | $ git show HEAD^:path/to/file |
b684f830 BF |
1548 | ------------------------------------------------- |
1549 | ||
1550 | which will display the given version of the file. | |
1551 | ||
7a7cc594 JH |
1552 | [[interrupted-work]] |
1553 | Temporarily setting aside work in progress | |
1554 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1555 | ||
1556 | While you are in the middle of working on something complicated, you | |
1557 | find an unrelated but obvious and trivial bug. You would like to fix it | |
5162e697 | 1558 | before continuing. You can use linkgit:git-stash[1] to save the current |
7a7cc594 JH |
1559 | state of your work, and after fixing the bug (or, optionally after doing |
1560 | so on a different branch and then coming back), unstash the | |
1561 | work-in-progress changes. | |
1562 | ||
1563 | ------------------------------------------------ | |
7a85f6ae | 1564 | $ git stash save "work in progress for foo feature" |
7a7cc594 JH |
1565 | ------------------------------------------------ |
1566 | ||
1567 | This command will save your changes away to the `stash`, and | |
1568 | reset your working tree and the index to match the tip of your | |
1569 | current branch. Then you can make your fix as usual. | |
1570 | ||
1571 | ------------------------------------------------ | |
1572 | ... edit and test ... | |
1573 | $ git commit -a -m "blorpl: typofix" | |
1574 | ------------------------------------------------ | |
1575 | ||
1576 | After that, you can go back to what you were working on with | |
7b8988e1 | 1577 | `git stash pop`: |
7a7cc594 JH |
1578 | |
1579 | ------------------------------------------------ | |
7b8988e1 | 1580 | $ git stash pop |
7a7cc594 JH |
1581 | ------------------------------------------------ |
1582 | ||
1583 | ||
e34caace | 1584 | [[ensuring-good-performance]] |
d19fbc3c BF |
1585 | Ensuring good performance |
1586 | ------------------------- | |
1587 | ||
2de9b711 | 1588 | On large repositories, Git depends on compression to keep the history |
901fd180 | 1589 | information from taking up too much space on disk or in memory. Some |
e1ebf212 | 1590 | Git commands may automatically run linkgit:git-gc[1], so you don't |
901fd180 TK |
1591 | have to worry about running it manually. However, compressing a large |
1592 | repository may take a while, so you may want to call `gc` explicitly | |
1593 | to avoid automatic compression kicking in when it is not convenient. | |
d19fbc3c | 1594 | |
e34caace BF |
1595 | |
1596 | [[ensuring-reliability]] | |
11e016a3 BF |
1597 | Ensuring reliability |
1598 | -------------------- | |
1599 | ||
e34caace | 1600 | [[checking-for-corruption]] |
11e016a3 BF |
1601 | Checking the repository for corruption |
1602 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1603 | ||
5162e697 | 1604 | The linkgit:git-fsck[1] command runs a number of self-consistency checks |
1191ee18 | 1605 | on the repository, and reports on any problems. This may take some |
c6a13b2c | 1606 | time. |
21dcb3b7 BF |
1607 | |
1608 | ------------------------------------------------- | |
04e50e94 | 1609 | $ git fsck |
21dcb3b7 BF |
1610 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 |
1611 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1612 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1613 | dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb | |
1614 | dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f | |
1615 | dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e | |
1616 | dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085 | |
1617 | dangling tree b24c2473f1fd3d91352a624795be026d64c8841f | |
1618 | ... | |
1619 | ------------------------------------------------- | |
1620 | ||
c6a13b2c JH |
1621 | You will see informational messages on dangling objects. They are objects |
1622 | that still exist in the repository but are no longer referenced by any of | |
1249d8ad | 1623 | your branches, and can (and will) be removed after a while with `gc`. |
b4ab1980 | 1624 | You can run `git fsck --no-dangling` to suppress these messages, and still |
c6a13b2c | 1625 | view real errors. |
1cdade2c | 1626 | |
e34caace | 1627 | [[recovering-lost-changes]] |
11e016a3 BF |
1628 | Recovering lost changes |
1629 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1630 | ||
e34caace | 1631 | [[reflogs]] |
559e4d7a BF |
1632 | Reflogs |
1633 | ^^^^^^^ | |
1634 | ||
1249d8ad TK |
1635 | Say you modify a branch with <<fixing-mistakes,`git reset --hard`>>, |
1636 | and then realize that the branch was the only reference you had to | |
1637 | that point in history. | |
559e4d7a | 1638 | |
2de9b711 | 1639 | Fortunately, Git also keeps a log, called a "reflog", of all the |
559e4d7a | 1640 | previous values of each branch. So in this case you can still find the |
a6080a0a | 1641 | old history using, for example, |
559e4d7a BF |
1642 | |
1643 | ------------------------------------------------- | |
1644 | $ git log master@{1} | |
1645 | ------------------------------------------------- | |
1646 | ||
e502c2c3 | 1647 | This lists the commits reachable from the previous version of the |
1249d8ad TK |
1648 | `master` branch head. This syntax can be used with any Git command |
1649 | that accepts a commit, not just with `git log`. Some other examples: | |
559e4d7a BF |
1650 | |
1651 | ------------------------------------------------- | |
1652 | $ git show master@{2} # See where the branch pointed 2, | |
1653 | $ git show master@{3} # 3, ... changes ago. | |
1654 | $ gitk master@{yesterday} # See where it pointed yesterday, | |
1655 | $ gitk master@{"1 week ago"} # ... or last week | |
953f3d6f BF |
1656 | $ git log --walk-reflogs master # show reflog entries for master |
1657 | ------------------------------------------------- | |
1658 | ||
1659 | A separate reflog is kept for the HEAD, so | |
1660 | ||
1661 | ------------------------------------------------- | |
1662 | $ git show HEAD@{"1 week ago"} | |
559e4d7a BF |
1663 | ------------------------------------------------- |
1664 | ||
953f3d6f BF |
1665 | will show what HEAD pointed to one week ago, not what the current branch |
1666 | pointed to one week ago. This allows you to see the history of what | |
1667 | you've checked out. | |
1668 | ||
559e4d7a | 1669 | The reflogs are kept by default for 30 days, after which they may be |
5162e697 | 1670 | pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn |
559e4d7a | 1671 | how to control this pruning, and see the "SPECIFYING REVISIONS" |
9d83e382 | 1672 | section of linkgit:gitrevisions[7] for details. |
559e4d7a | 1673 | |
2de9b711 | 1674 | Note that the reflog history is very different from normal Git history. |
559e4d7a BF |
1675 | While normal history is shared by every repository that works on the |
1676 | same project, the reflog history is not shared: it tells you only about | |
1677 | how the branches in your local repository have changed over time. | |
1678 | ||
59723040 | 1679 | [[dangling-object-recovery]] |
559e4d7a BF |
1680 | Examining dangling objects |
1681 | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
1682 | ||
59723040 BF |
1683 | In some situations the reflog may not be able to save you. For example, |
1684 | suppose you delete a branch, then realize you need the history it | |
1685 | contained. The reflog is also deleted; however, if you have not yet | |
1686 | pruned the repository, then you may still be able to find the lost | |
6127c086 | 1687 | commits in the dangling objects that `git fsck` reports. See |
59723040 | 1688 | <<dangling-objects>> for the details. |
559e4d7a BF |
1689 | |
1690 | ------------------------------------------------- | |
1691 | $ git fsck | |
1692 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 | |
1693 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1694 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1695 | ... | |
1696 | ------------------------------------------------- | |
1697 | ||
aacd404e | 1698 | You can examine |
559e4d7a BF |
1699 | one of those dangling commits with, for example, |
1700 | ||
1701 | ------------------------------------------------ | |
1702 | $ gitk 7281251ddd --not --all | |
1703 | ------------------------------------------------ | |
1704 | ||
1705 | which does what it sounds like: it says that you want to see the commit | |
1706 | history that is described by the dangling commit(s), but not the | |
1707 | history that is described by all your existing branches and tags. Thus | |
1708 | you get exactly the history reachable from that commit that is lost. | |
1709 | (And notice that it might not be just one commit: we only report the | |
1710 | "tip of the line" as being dangling, but there might be a whole deep | |
79c96c57 | 1711 | and complex commit history that was dropped.) |
559e4d7a BF |
1712 | |
1713 | If you decide you want the history back, you can always create a new | |
1714 | reference pointing to it, for example, a new branch: | |
1715 | ||
1716 | ------------------------------------------------ | |
a6080a0a | 1717 | $ git branch recovered-branch 7281251ddd |
559e4d7a BF |
1718 | ------------------------------------------------ |
1719 | ||
59723040 BF |
1720 | Other types of dangling objects (blobs and trees) are also possible, and |
1721 | dangling objects can arise in other situations. | |
1722 | ||
11e016a3 | 1723 | |
e34caace | 1724 | [[sharing-development]] |
d19fbc3c | 1725 | Sharing development with others |
b684f830 | 1726 | =============================== |
d19fbc3c | 1727 | |
aa971cb9 | 1728 | [[getting-updates-With-git-pull]] |
6127c086 | 1729 | Getting updates with git pull |
b684f830 | 1730 | ----------------------------- |
d19fbc3c | 1731 | |
e63ec003 | 1732 | After you clone a repository and commit a few changes of your own, you |
d19fbc3c BF |
1733 | may wish to check the original repository for updates and merge them |
1734 | into your own work. | |
1735 | ||
aa971cb9 | 1736 | We have already seen <<Updating-a-repository-With-git-fetch,how to |
0e615b25 | 1737 | keep remote-tracking branches up to date>> with linkgit:git-fetch[1], |
d19fbc3c BF |
1738 | and how to merge two branches. So you can merge in changes from the |
1739 | original repository's master branch with: | |
1740 | ||
1741 | ------------------------------------------------- | |
1742 | $ git fetch | |
1743 | $ git merge origin/master | |
1744 | ------------------------------------------------- | |
1745 | ||
5162e697 | 1746 | However, the linkgit:git-pull[1] command provides a way to do this in |
d19fbc3c BF |
1747 | one step: |
1748 | ||
1749 | ------------------------------------------------- | |
1750 | $ git pull origin master | |
1751 | ------------------------------------------------- | |
1752 | ||
1249d8ad TK |
1753 | In fact, if you have `master` checked out, then this branch has been |
1754 | configured by `git clone` to get changes from the HEAD branch of the | |
66a062a1 | 1755 | origin repository. So often you can |
0eb4f7cd | 1756 | accomplish the above with just a simple |
d19fbc3c BF |
1757 | |
1758 | ------------------------------------------------- | |
1759 | $ git pull | |
1760 | ------------------------------------------------- | |
1761 | ||
66a062a1 MM |
1762 | This command will fetch changes from the remote branches to your |
1763 | remote-tracking branches `origin/*`, and merge the default branch into | |
1764 | the current branch. | |
1765 | ||
29b9a66f MM |
1766 | More generally, a branch that is created from a remote-tracking branch |
1767 | will pull | |
0eb4f7cd | 1768 | by default from that branch. See the descriptions of the |
1249d8ad | 1769 | `branch.<name>.remote` and `branch.<name>.merge` options in |
5162e697 DM |
1770 | linkgit:git-config[1], and the discussion of the `--track` option in |
1771 | linkgit:git-checkout[1], to learn how to control these defaults. | |
d19fbc3c | 1772 | |
1249d8ad | 1773 | In addition to saving you keystrokes, `git pull` also helps you by |
d19fbc3c BF |
1774 | producing a default commit message documenting the branch and |
1775 | repository that you pulled from. | |
1776 | ||
1777 | (But note that no such commit will be created in the case of a | |
a75d7b54 | 1778 | <<fast-forwards,fast-forward>>; instead, your branch will just be |
79c96c57 | 1779 | updated to point to the latest commit from the upstream branch.) |
d19fbc3c | 1780 | |
1249d8ad | 1781 | The `git pull` command can also be given `.` as the "remote" repository, |
1191ee18 | 1782 | in which case it just merges in a branch from the current repository; so |
4c63ff45 BF |
1783 | the commands |
1784 | ||
1785 | ------------------------------------------------- | |
1786 | $ git pull . branch | |
1787 | $ git merge branch | |
1788 | ------------------------------------------------- | |
1789 | ||
1790 | are roughly equivalent. The former is actually very commonly used. | |
1791 | ||
e34caace | 1792 | [[submitting-patches]] |
d19fbc3c | 1793 | Submitting patches to a project |
b684f830 | 1794 | ------------------------------- |
d19fbc3c BF |
1795 | |
1796 | If you just have a few changes, the simplest way to submit them may | |
1797 | just be to send them as patches in email: | |
1798 | ||
5162e697 | 1799 | First, use linkgit:git-format-patch[1]; for example: |
d19fbc3c BF |
1800 | |
1801 | ------------------------------------------------- | |
eb6ae7f4 | 1802 | $ git format-patch origin |
d19fbc3c BF |
1803 | ------------------------------------------------- |
1804 | ||
1805 | will produce a numbered series of files in the current directory, one | |
1249d8ad | 1806 | for each patch in the current branch but not in `origin/HEAD`. |
d19fbc3c | 1807 | |
d84cef18 PO |
1808 | `git format-patch` can include an initial "cover letter". You can insert |
1809 | commentary on individual patches after the three dash line which | |
1810 | `format-patch` places after the commit message but before the patch | |
1811 | itself. If you use `git notes` to track your cover letter material, | |
1812 | `git format-patch --notes` will include the commit's notes in a similar | |
1813 | manner. | |
1814 | ||
d19fbc3c BF |
1815 | You can then import these into your mail client and send them by |
1816 | hand. However, if you have a lot to send at once, you may prefer to | |
5162e697 | 1817 | use the linkgit:git-send-email[1] script to automate the process. |
d19fbc3c BF |
1818 | Consult the mailing list for your project first to determine how they |
1819 | prefer such patches be handled. | |
1820 | ||
e34caace | 1821 | [[importing-patches]] |
d19fbc3c | 1822 | Importing patches to a project |
b684f830 | 1823 | ------------------------------ |
d19fbc3c | 1824 | |
5162e697 | 1825 | Git also provides a tool called linkgit:git-am[1] (am stands for |
d19fbc3c BF |
1826 | "apply mailbox"), for importing such an emailed series of patches. |
1827 | Just save all of the patch-containing messages, in order, into a | |
1249d8ad | 1828 | single mailbox file, say `patches.mbox`, then run |
d19fbc3c BF |
1829 | |
1830 | ------------------------------------------------- | |
eb6ae7f4 | 1831 | $ git am -3 patches.mbox |
d19fbc3c BF |
1832 | ------------------------------------------------- |
1833 | ||
1834 | Git will apply each patch in order; if any conflicts are found, it | |
1835 | will stop, and you can fix the conflicts as described in | |
1249d8ad | 1836 | "<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells |
2de9b711 | 1837 | Git to perform a merge; if you would prefer it just to abort and |
01997b4a BF |
1838 | leave your tree and index untouched, you may omit that option.) |
1839 | ||
1840 | Once the index is updated with the results of the conflict | |
1841 | resolution, instead of creating a new commit, just run | |
d19fbc3c BF |
1842 | |
1843 | ------------------------------------------------- | |
8ceb6fbd | 1844 | $ git am --continue |
d19fbc3c BF |
1845 | ------------------------------------------------- |
1846 | ||
2de9b711 | 1847 | and Git will create the commit for you and continue applying the |
d19fbc3c BF |
1848 | remaining patches from the mailbox. |
1849 | ||
1850 | The final result will be a series of commits, one for each patch in | |
1851 | the original mailbox, with authorship and commit log message each | |
1852 | taken from the message containing each patch. | |
1853 | ||
eda69449 | 1854 | [[public-repositories]] |
2de9b711 | 1855 | Public Git repositories |
eda69449 | 1856 | ----------------------- |
d19fbc3c | 1857 | |
6e30fb0c DK |
1858 | Another way to submit changes to a project is to tell the maintainer |
1859 | of that project to pull the changes from your repository using | |
aa971cb9 | 1860 | linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull, |
6127c086 | 1861 | Getting updates with `git pull`>>" we described this as a way to get |
6e30fb0c DK |
1862 | updates from the "main" repository, but it works just as well in the |
1863 | other direction. | |
d19fbc3c | 1864 | |
eda69449 BF |
1865 | If you and the maintainer both have accounts on the same machine, then |
1866 | you can just pull changes from each other's repositories directly; | |
11d51533 | 1867 | commands that accept repository URLs as arguments will also accept a |
eda69449 | 1868 | local directory name: |
d19fbc3c BF |
1869 | |
1870 | ------------------------------------------------- | |
1871 | $ git clone /path/to/repository | |
1872 | $ git pull /path/to/other/repository | |
1873 | ------------------------------------------------- | |
1874 | ||
c9016158 | 1875 | or an ssh URL: |
11d51533 BF |
1876 | |
1877 | ------------------------------------------------- | |
1878 | $ git clone ssh://yourhost/~you/repository | |
1879 | ------------------------------------------------- | |
1880 | ||
1881 | For projects with few developers, or for synchronizing a few private | |
1882 | repositories, this may be all you need. | |
1883 | ||
eda69449 BF |
1884 | However, the more common way to do this is to maintain a separate public |
1885 | repository (usually on a different host) for others to pull changes | |
1886 | from. This is usually more convenient, and allows you to cleanly | |
1887 | separate private work in progress from publicly visible work. | |
d19fbc3c BF |
1888 | |
1889 | You will continue to do your day-to-day work in your personal | |
1890 | repository, but periodically "push" changes from your personal | |
1891 | repository into your public repository, allowing other developers to | |
1892 | pull from that repository. So the flow of changes, in a situation | |
1893 | where there is one other developer with a public repository, looks | |
1894 | like this: | |
1895 | ||
1896 | you push | |
1897 | your personal repo ------------------> your public repo | |
a6080a0a | 1898 | ^ | |
d19fbc3c BF |
1899 | | | |
1900 | | you pull | they pull | |
1901 | | | | |
1902 | | | | |
1903 | | they push V | |
1904 | their public repo <------------------- their repo | |
1905 | ||
11d51533 BF |
1906 | We explain how to do this in the following sections. |
1907 | ||
eda69449 BF |
1908 | [[setting-up-a-public-repository]] |
1909 | Setting up a public repository | |
1910 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1911 | ||
1249d8ad | 1912 | Assume your personal repository is in the directory `~/proj`. We |
6127c086 | 1913 | first create a new clone of the repository and tell `git daemon` that it |
eda69449 | 1914 | is meant to be public: |
d19fbc3c BF |
1915 | |
1916 | ------------------------------------------------- | |
52c80037 | 1917 | $ git clone --bare ~/proj proj.git |
eda69449 | 1918 | $ touch proj.git/git-daemon-export-ok |
d19fbc3c BF |
1919 | ------------------------------------------------- |
1920 | ||
52c80037 | 1921 | The resulting directory proj.git contains a "bare" git repository--it is |
1249d8ad | 1922 | just the contents of the `.git` directory, without any files checked out |
eda69449 | 1923 | around it. |
d19fbc3c | 1924 | |
1249d8ad | 1925 | Next, copy `proj.git` to the server where you plan to host the |
d19fbc3c BF |
1926 | public repository. You can use scp, rsync, or whatever is most |
1927 | convenient. | |
1928 | ||
eda69449 | 1929 | [[exporting-via-git]] |
2de9b711 | 1930 | Exporting a Git repository via the Git protocol |
eda69449 BF |
1931 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
1932 | ||
1933 | This is the preferred method. | |
1934 | ||
1935 | If someone else administers the server, they should tell you what | |
1249d8ad TK |
1936 | directory to put the repository in, and what `git://` URL it will |
1937 | appear at. You can then skip to the section | |
d19fbc3c BF |
1938 | "<<pushing-changes-to-a-public-repository,Pushing changes to a public |
1939 | repository>>", below. | |
1940 | ||
5162e697 | 1941 | Otherwise, all you need to do is start linkgit:git-daemon[1]; it will |
eda69449 | 1942 | listen on port 9418. By default, it will allow access to any directory |
2de9b711 | 1943 | that looks like a Git directory and contains the magic file |
6127c086 | 1944 | git-daemon-export-ok. Passing some directory paths as `git daemon` |
eda69449 BF |
1945 | arguments will further restrict the exports to those paths. |
1946 | ||
6127c086 | 1947 | You can also run `git daemon` as an inetd service; see the |
5162e697 | 1948 | linkgit:git-daemon[1] man page for details. (See especially the |
eda69449 | 1949 | examples section.) |
d19fbc3c BF |
1950 | |
1951 | [[exporting-via-http]] | |
de3f2c7b | 1952 | Exporting a git repository via HTTP |
eda69449 | 1953 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c | 1954 | |
2de9b711 | 1955 | The Git protocol gives better performance and reliability, but on a |
de3f2c7b | 1956 | host with a web server set up, HTTP exports may be simpler to set up. |
d19fbc3c | 1957 | |
2de9b711 | 1958 | All you need to do is place the newly created bare Git repository in |
d19fbc3c BF |
1959 | a directory that is exported by the web server, and make some |
1960 | adjustments to give web clients some extra information they need: | |
1961 | ||
1962 | ------------------------------------------------- | |
1963 | $ mv proj.git /home/you/public_html/proj.git | |
1964 | $ cd proj.git | |
c64415e2 | 1965 | $ git --bare update-server-info |
7dce9918 | 1966 | $ mv hooks/post-update.sample hooks/post-update |
d19fbc3c BF |
1967 | ------------------------------------------------- |
1968 | ||
1969 | (For an explanation of the last two lines, see | |
6998e4db | 1970 | linkgit:git-update-server-info[1] and linkgit:githooks[5].) |
d19fbc3c | 1971 | |
1249d8ad | 1972 | Advertise the URL of `proj.git`. Anybody else should then be able to |
c9016158 | 1973 | clone or pull from that URL, for example with a command line like: |
d19fbc3c BF |
1974 | |
1975 | ------------------------------------------------- | |
1976 | $ git clone http://yourserver.com/~you/proj.git | |
1977 | ------------------------------------------------- | |
1978 | ||
1979 | (See also | |
1980 | link:howto/setup-git-server-over-http.txt[setup-git-server-over-http] | |
1981 | for a slightly more sophisticated setup using WebDAV which also | |
de3f2c7b | 1982 | allows pushing over HTTP.) |
d19fbc3c | 1983 | |
d19fbc3c BF |
1984 | [[pushing-changes-to-a-public-repository]] |
1985 | Pushing changes to a public repository | |
eda69449 | 1986 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c | 1987 | |
eda69449 | 1988 | Note that the two techniques outlined above (exporting via |
d19fbc3c BF |
1989 | <<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other |
1990 | maintainers to fetch your latest changes, but they do not allow write | |
1991 | access, which you will need to update the public repository with the | |
1992 | latest changes created in your private repository. | |
1993 | ||
5162e697 | 1994 | The simplest way to do this is using linkgit:git-push[1] and ssh; to |
1249d8ad TK |
1995 | update the remote branch named `master` with the latest state of your |
1996 | branch named `master`, run | |
d19fbc3c BF |
1997 | |
1998 | ------------------------------------------------- | |
1999 | $ git push ssh://yourserver.com/~you/proj.git master:master | |
2000 | ------------------------------------------------- | |
2001 | ||
2002 | or just | |
2003 | ||
2004 | ------------------------------------------------- | |
2005 | $ git push ssh://yourserver.com/~you/proj.git master | |
2006 | ------------------------------------------------- | |
2007 | ||
6127c086 | 2008 | As with `git fetch`, `git push` will complain if this does not result in a |
a75d7b54 | 2009 | <<fast-forwards,fast-forward>>; see the following section for details on |
81eb417a | 2010 | handling this case. |
d19fbc3c | 2011 | |
1249d8ad | 2012 | Note that the target of a `push` is normally a |
11d51533 | 2013 | <<def_bare_repository,bare>> repository. You can also push to a |
d9be2485 TK |
2014 | repository that has a checked-out working tree, but a push to update the |
2015 | currently checked-out branch is denied by default to prevent confusion. | |
50995edd | 2016 | See the description of the receive.denyCurrentBranch option |
d9be2485 | 2017 | in linkgit:git-config[1] for details. |
11d51533 | 2018 | |
6127c086 | 2019 | As with `git fetch`, you may also set up configuration options to |
e9b49083 TK |
2020 | save typing; so, for example: |
2021 | ||
2022 | ------------------------------------------------- | |
2023 | $ git remote add public-repo ssh://yourserver.com/~you/proj.git | |
2024 | ------------------------------------------------- | |
2025 | ||
2026 | adds the following to `.git/config`: | |
d19fbc3c BF |
2027 | |
2028 | ------------------------------------------------- | |
d19fbc3c | 2029 | [remote "public-repo"] |
e9b49083 TK |
2030 | url = yourserver.com:proj.git |
2031 | fetch = +refs/heads/*:refs/remotes/example/* | |
d19fbc3c BF |
2032 | ------------------------------------------------- |
2033 | ||
e9b49083 | 2034 | which lets you do the same push with just |
d19fbc3c BF |
2035 | |
2036 | ------------------------------------------------- | |
2037 | $ git push public-repo master | |
2038 | ------------------------------------------------- | |
2039 | ||
1249d8ad TK |
2040 | See the explanations of the `remote.<name>.url`, |
2041 | `branch.<name>.remote`, and `remote.<name>.push` options in | |
2042 | linkgit:git-config[1] for details. | |
d19fbc3c | 2043 | |
81eb417a BF |
2044 | [[forcing-push]] |
2045 | What to do when a push fails | |
2046 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
2047 | ||
a75d7b54 | 2048 | If a push would not result in a <<fast-forwards,fast-forward>> of the |
81eb417a BF |
2049 | remote branch, then it will fail with an error like: |
2050 | ||
2051 | ------------------------------------------------- | |
2052 | error: remote 'refs/heads/master' is not an ancestor of | |
2053 | local 'refs/heads/master'. | |
2054 | Maybe you are not up-to-date and need to pull first? | |
2055 | error: failed to push to 'ssh://yourserver.com/~you/proj.git' | |
2056 | ------------------------------------------------- | |
2057 | ||
2058 | This can happen, for example, if you: | |
2059 | ||
6127c086 FC |
2060 | - use `git reset --hard` to remove already-published commits, or |
2061 | - use `git commit --amend` to replace already-published commits | |
7cb192ea | 2062 | (as in <<fixing-a-mistake-by-rewriting-history>>), or |
6127c086 | 2063 | - use `git rebase` to rebase any already-published commits (as |
81eb417a BF |
2064 | in <<using-git-rebase>>). |
2065 | ||
6127c086 | 2066 | You may force `git push` to perform the update anyway by preceding the |
81eb417a BF |
2067 | branch name with a plus sign: |
2068 | ||
2069 | ------------------------------------------------- | |
2070 | $ git push ssh://yourserver.com/~you/proj.git +master | |
2071 | ------------------------------------------------- | |
2072 | ||
d1471e06 TK |
2073 | Note the addition of the `+` sign. Alternatively, you can use the |
2074 | `-f` flag to force the remote update, as in: | |
2075 | ||
2076 | ------------------------------------------------- | |
2077 | $ git push -f ssh://yourserver.com/~you/proj.git master | |
2078 | ------------------------------------------------- | |
2079 | ||
81eb417a | 2080 | Normally whenever a branch head in a public repository is modified, it |
9e5d87d4 | 2081 | is modified to point to a descendant of the commit that it pointed to |
81eb417a | 2082 | before. By forcing a push in this situation, you break that convention. |
aa971cb9 | 2083 | (See <<problems-With-rewriting-history>>.) |
81eb417a BF |
2084 | |
2085 | Nevertheless, this is a common practice for people that need a simple | |
2086 | way to publish a work-in-progress patch series, and it is an acceptable | |
2087 | compromise as long as you warn other developers that this is how you | |
2088 | intend to manage the branch. | |
2089 | ||
2090 | It's also possible for a push to fail in this way when other people have | |
2091 | the right to push to the same repository. In that case, the correct | |
843c81dc EH |
2092 | solution is to retry the push after first updating your work: either by a |
2093 | pull, or by a fetch followed by a rebase; see the | |
81eb417a | 2094 | <<setting-up-a-shared-repository,next section>> and |
6998e4db | 2095 | linkgit:gitcvs-migration[7] for more. |
81eb417a | 2096 | |
e34caace | 2097 | [[setting-up-a-shared-repository]] |
d19fbc3c | 2098 | Setting up a shared repository |
eda69449 | 2099 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
d19fbc3c BF |
2100 | |
2101 | Another way to collaborate is by using a model similar to that | |
2102 | commonly used in CVS, where several developers with special rights | |
2103 | all push to and pull from a single shared repository. See | |
6998e4db | 2104 | linkgit:gitcvs-migration[7] for instructions on how to |
d19fbc3c BF |
2105 | set this up. |
2106 | ||
2de9b711 | 2107 | However, while there is nothing wrong with Git's support for shared |
8fae2225 | 2108 | repositories, this mode of operation is not generally recommended, |
2de9b711 | 2109 | simply because the mode of collaboration that Git supports--by |
8fae2225 BF |
2110 | exchanging patches and pulling from public repositories--has so many |
2111 | advantages over the central shared repository: | |
2112 | ||
2113 | - Git's ability to quickly import and merge patches allows a | |
2114 | single maintainer to process incoming changes even at very | |
6127c086 | 2115 | high rates. And when that becomes too much, `git pull` provides |
8fae2225 BF |
2116 | an easy way for that maintainer to delegate this job to other |
2117 | maintainers while still allowing optional review of incoming | |
2118 | changes. | |
2119 | - Since every developer's repository has the same complete copy | |
2120 | of the project history, no repository is special, and it is | |
2121 | trivial for another developer to take over maintenance of a | |
2122 | project, either by mutual agreement, or because a maintainer | |
2123 | becomes unresponsive or difficult to work with. | |
2124 | - The lack of a central group of "committers" means there is | |
2125 | less need for formal decisions about who is "in" and who is | |
2126 | "out". | |
2127 | ||
e34caace | 2128 | [[setting-up-gitweb]] |
eda69449 BF |
2129 | Allowing web browsing of a repository |
2130 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
d19fbc3c | 2131 | |
a8cd1402 | 2132 | The gitweb cgi script provides users an easy way to browse your |
2de9b711 TA |
2133 | project's files and history without having to install Git; see the file |
2134 | gitweb/INSTALL in the Git source tree for instructions on setting it up. | |
d19fbc3c | 2135 | |
e34caace | 2136 | [[sharing-development-examples]] |
b684f830 BF |
2137 | Examples |
2138 | -------- | |
d19fbc3c | 2139 | |
9e2163ea BF |
2140 | [[maintaining-topic-branches]] |
2141 | Maintaining topic branches for a Linux subsystem maintainer | |
2142 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
2143 | ||
2de9b711 | 2144 | This describes how Tony Luck uses Git in his role as maintainer of the |
9e2163ea BF |
2145 | IA64 architecture for the Linux kernel. |
2146 | ||
2147 | He uses two public branches: | |
2148 | ||
2149 | - A "test" tree into which patches are initially placed so that they | |
2150 | can get some exposure when integrated with other ongoing development. | |
2151 | This tree is available to Andrew for pulling into -mm whenever he | |
2152 | wants. | |
2153 | ||
2154 | - A "release" tree into which tested patches are moved for final sanity | |
2155 | checking, and as a vehicle to send them upstream to Linus (by sending | |
2156 | him a "please pull" request.) | |
2157 | ||
2158 | He also uses a set of temporary branches ("topic branches"), each | |
2159 | containing a logical grouping of patches. | |
2160 | ||
2161 | To set this up, first create your work tree by cloning Linus's public | |
2162 | tree: | |
2163 | ||
2164 | ------------------------------------------------- | |
283efb01 | 2165 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work |
9e2163ea BF |
2166 | $ cd work |
2167 | ------------------------------------------------- | |
2168 | ||
29b9a66f | 2169 | Linus's tree will be stored in the remote-tracking branch named origin/master, |
5162e697 DM |
2170 | and can be updated using linkgit:git-fetch[1]; you can track other |
2171 | public trees using linkgit:git-remote[1] to set up a "remote" and | |
2172 | linkgit:git-fetch[1] to keep them up-to-date; see | |
6e30fb0c | 2173 | <<repositories-and-branches>>. |
9e2163ea BF |
2174 | |
2175 | Now create the branches in which you are going to work; these start out | |
2176 | at the current tip of origin/master branch, and should be set up (using | |
1249d8ad | 2177 | the `--track` option to linkgit:git-branch[1]) to merge changes in from |
9e2163ea BF |
2178 | Linus by default. |
2179 | ||
2180 | ------------------------------------------------- | |
2181 | $ git branch --track test origin/master | |
2182 | $ git branch --track release origin/master | |
2183 | ------------------------------------------------- | |
2184 | ||
5162e697 | 2185 | These can be easily kept up to date using linkgit:git-pull[1]. |
9e2163ea BF |
2186 | |
2187 | ------------------------------------------------- | |
2188 | $ git checkout test && git pull | |
2189 | $ git checkout release && git pull | |
2190 | ------------------------------------------------- | |
2191 | ||
2192 | Important note! If you have any local changes in these branches, then | |
2193 | this merge will create a commit object in the history (with no local | |
2de9b711 | 2194 | changes Git will simply do a "fast-forward" merge). Many people dislike |
9e2163ea | 2195 | the "noise" that this creates in the Linux history, so you should avoid |
1249d8ad | 2196 | doing this capriciously in the `release` branch, as these noisy commits |
9e2163ea BF |
2197 | will become part of the permanent history when you ask Linus to pull |
2198 | from the release branch. | |
2199 | ||
5162e697 | 2200 | A few configuration variables (see linkgit:git-config[1]) can |
9e2163ea BF |
2201 | make it easy to push both branches to your public tree. (See |
2202 | <<setting-up-a-public-repository>>.) | |
2203 | ||
2204 | ------------------------------------------------- | |
2205 | $ cat >> .git/config <<EOF | |
2206 | [remote "mytree"] | |
283efb01 | 2207 | url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git |
9e2163ea BF |
2208 | push = release |
2209 | push = test | |
2210 | EOF | |
2211 | ------------------------------------------------- | |
2212 | ||
2213 | Then you can push both the test and release trees using | |
5162e697 | 2214 | linkgit:git-push[1]: |
9e2163ea BF |
2215 | |
2216 | ------------------------------------------------- | |
2217 | $ git push mytree | |
2218 | ------------------------------------------------- | |
2219 | ||
2220 | or push just one of the test and release branches using: | |
2221 | ||
2222 | ------------------------------------------------- | |
2223 | $ git push mytree test | |
2224 | ------------------------------------------------- | |
2225 | ||
2226 | or | |
2227 | ||
2228 | ------------------------------------------------- | |
2229 | $ git push mytree release | |
2230 | ------------------------------------------------- | |
2231 | ||
2232 | Now to apply some patches from the community. Think of a short | |
2233 | snappy name for a branch to hold this patch (or related group of | |
352953a5 TL |
2234 | patches), and create a new branch from a recent stable tag of |
2235 | Linus's branch. Picking a stable base for your branch will: | |
2236 | 1) help you: by avoiding inclusion of unrelated and perhaps lightly | |
2237 | tested changes | |
1249d8ad | 2238 | 2) help future bug hunters that use `git bisect` to find problems |
9e2163ea BF |
2239 | |
2240 | ------------------------------------------------- | |
352953a5 | 2241 | $ git checkout -b speed-up-spinlocks v2.6.35 |
9e2163ea BF |
2242 | ------------------------------------------------- |
2243 | ||
2244 | Now you apply the patch(es), run some tests, and commit the change(s). If | |
2245 | the patch is a multi-part series, then you should apply each as a separate | |
2246 | commit to this branch. | |
2247 | ||
2248 | ------------------------------------------------- | |
2249 | $ ... patch ... test ... commit [ ... patch ... test ... commit ]* | |
2250 | ------------------------------------------------- | |
2251 | ||
2252 | When you are happy with the state of this change, you can pull it into the | |
2253 | "test" branch in preparation to make it public: | |
2254 | ||
2255 | ------------------------------------------------- | |
2256 | $ git checkout test && git pull . speed-up-spinlocks | |
2257 | ------------------------------------------------- | |
2258 | ||
2259 | It is unlikely that you would have any conflicts here ... but you might if you | |
2260 | spent a while on this step and had also pulled new versions from upstream. | |
2261 | ||
2262 | Some time later when enough time has passed and testing done, you can pull the | |
1249d8ad | 2263 | same branch into the `release` tree ready to go upstream. This is where you |
9e2163ea | 2264 | see the value of keeping each patch (or patch series) in its own branch. It |
1249d8ad | 2265 | means that the patches can be moved into the `release` tree in any order. |
9e2163ea BF |
2266 | |
2267 | ------------------------------------------------- | |
2268 | $ git checkout release && git pull . speed-up-spinlocks | |
2269 | ------------------------------------------------- | |
2270 | ||
2271 | After a while, you will have a number of branches, and despite the | |
2272 | well chosen names you picked for each of them, you may forget what | |
2273 | they are for, or what status they are in. To get a reminder of what | |
2274 | changes are in a specific branch, use: | |
2275 | ||
2276 | ------------------------------------------------- | |
467c0197 | 2277 | $ git log linux..branchname | git shortlog |
9e2163ea BF |
2278 | ------------------------------------------------- |
2279 | ||
06ada152 | 2280 | To see whether it has already been merged into the test or release branches, |
9e2163ea BF |
2281 | use: |
2282 | ||
2283 | ------------------------------------------------- | |
2284 | $ git log test..branchname | |
2285 | ------------------------------------------------- | |
2286 | ||
2287 | or | |
2288 | ||
2289 | ------------------------------------------------- | |
2290 | $ git log release..branchname | |
2291 | ------------------------------------------------- | |
2292 | ||
06ada152 | 2293 | (If this branch has not yet been merged, you will see some log entries. |
9e2163ea BF |
2294 | If it has been merged, then there will be no output.) |
2295 | ||
2296 | Once a patch completes the great cycle (moving from test to release, | |
2297 | then pulled by Linus, and finally coming back into your local | |
1249d8ad | 2298 | `origin/master` branch), the branch for this change is no longer needed. |
9e2163ea BF |
2299 | You detect this when the output from: |
2300 | ||
2301 | ------------------------------------------------- | |
2302 | $ git log origin..branchname | |
2303 | ------------------------------------------------- | |
2304 | ||
2305 | is empty. At this point the branch can be deleted: | |
2306 | ||
2307 | ------------------------------------------------- | |
2308 | $ git branch -d branchname | |
2309 | ------------------------------------------------- | |
2310 | ||
2311 | Some changes are so trivial that it is not necessary to create a separate | |
2312 | branch and then merge into each of the test and release branches. For | |
1249d8ad TK |
2313 | these changes, just apply directly to the `release` branch, and then |
2314 | merge that into the `test` branch. | |
9e2163ea | 2315 | |
ae6ef554 TK |
2316 | After pushing your work to `mytree`, you can use |
2317 | linkgit:git-request-pull[1] to prepare a "please pull" request message | |
2318 | to send to Linus: | |
9e2163ea BF |
2319 | |
2320 | ------------------------------------------------- | |
ae6ef554 TK |
2321 | $ git push mytree |
2322 | $ git request-pull origin mytree release | |
9e2163ea BF |
2323 | ------------------------------------------------- |
2324 | ||
2325 | Here are some of the scripts that simplify all this even further. | |
2326 | ||
2327 | ------------------------------------------------- | |
2328 | ==== update script ==== | |
48a8c26c | 2329 | # Update a branch in my Git tree. If the branch to be updated |
9e2163ea BF |
2330 | # is origin, then pull from kernel.org. Otherwise merge |
2331 | # origin/master branch into test|release branch | |
2332 | ||
2333 | case "$1" in | |
2334 | test|release) | |
2335 | git checkout $1 && git pull . origin | |
2336 | ;; | |
2337 | origin) | |
fc74ecc1 | 2338 | before=$(git rev-parse refs/remotes/origin/master) |
9e2163ea | 2339 | git fetch origin |
fc74ecc1 | 2340 | after=$(git rev-parse refs/remotes/origin/master) |
9e2163ea BF |
2341 | if [ $before != $after ] |
2342 | then | |
2343 | git log $before..$after | git shortlog | |
2344 | fi | |
2345 | ;; | |
2346 | *) | |
1a2ba8b9 | 2347 | echo "usage: $0 origin|test|release" 1>&2 |
9e2163ea BF |
2348 | exit 1 |
2349 | ;; | |
2350 | esac | |
2351 | ------------------------------------------------- | |
2352 | ||
2353 | ------------------------------------------------- | |
2354 | ==== merge script ==== | |
2355 | # Merge a branch into either the test or release branch | |
2356 | ||
2357 | pname=$0 | |
2358 | ||
2359 | usage() | |
2360 | { | |
1a2ba8b9 | 2361 | echo "usage: $pname branch test|release" 1>&2 |
9e2163ea BF |
2362 | exit 1 |
2363 | } | |
2364 | ||
fc74ecc1 | 2365 | git show-ref -q --verify -- refs/heads/"$1" || { |
9e2163ea BF |
2366 | echo "Can't see branch <$1>" 1>&2 |
2367 | usage | |
fc74ecc1 | 2368 | } |
9e2163ea BF |
2369 | |
2370 | case "$2" in | |
2371 | test|release) | |
2372 | if [ $(git log $2..$1 | wc -c) -eq 0 ] | |
2373 | then | |
2374 | echo $1 already merged into $2 1>&2 | |
2375 | exit 1 | |
2376 | fi | |
2377 | git checkout $2 && git pull . $1 | |
2378 | ;; | |
2379 | *) | |
2380 | usage | |
2381 | ;; | |
2382 | esac | |
2383 | ------------------------------------------------- | |
2384 | ||
2385 | ------------------------------------------------- | |
2386 | ==== status script ==== | |
48a8c26c | 2387 | # report on status of my ia64 Git tree |
9e2163ea BF |
2388 | |
2389 | gb=$(tput setab 2) | |
2390 | rb=$(tput setab 1) | |
2391 | restore=$(tput setab 9) | |
2392 | ||
2393 | if [ `git rev-list test..release | wc -c` -gt 0 ] | |
2394 | then | |
2395 | echo $rb Warning: commits in release that are not in test $restore | |
2396 | git log test..release | |
2397 | fi | |
2398 | ||
fc74ecc1 | 2399 | for branch in `git show-ref --heads | sed 's|^.*/||'` |
9e2163ea BF |
2400 | do |
2401 | if [ $branch = test -o $branch = release ] | |
2402 | then | |
2403 | continue | |
2404 | fi | |
2405 | ||
2406 | echo -n $gb ======= $branch ====== $restore " " | |
2407 | status= | |
2408 | for ref in test release origin/master | |
2409 | do | |
2410 | if [ `git rev-list $ref..$branch | wc -c` -gt 0 ] | |
2411 | then | |
2412 | status=$status${ref:0:1} | |
2413 | fi | |
2414 | done | |
2415 | case $status in | |
2416 | trl) | |
2417 | echo $rb Need to pull into test $restore | |
2418 | ;; | |
2419 | rl) | |
2420 | echo "In test" | |
2421 | ;; | |
2422 | l) | |
2423 | echo "Waiting for linus" | |
2424 | ;; | |
2425 | "") | |
2426 | echo $rb All done $restore | |
2427 | ;; | |
2428 | *) | |
2429 | echo $rb "<$status>" $restore | |
2430 | ;; | |
2431 | esac | |
2432 | git log origin/master..$branch | git shortlog | |
2433 | done | |
2434 | ------------------------------------------------- | |
d19fbc3c | 2435 | |
d19fbc3c | 2436 | |
d19fbc3c | 2437 | [[cleaning-up-history]] |
4c63ff45 BF |
2438 | Rewriting history and maintaining patch series |
2439 | ============================================== | |
2440 | ||
2441 | Normally commits are only added to a project, never taken away or | |
2442 | replaced. Git is designed with this assumption, and violating it will | |
2de9b711 | 2443 | cause Git's merge machinery (for example) to do the wrong thing. |
4c63ff45 BF |
2444 | |
2445 | However, there is a situation in which it can be useful to violate this | |
2446 | assumption. | |
2447 | ||
e34caace | 2448 | [[patch-series]] |
4c63ff45 BF |
2449 | Creating the perfect patch series |
2450 | --------------------------------- | |
2451 | ||
2452 | Suppose you are a contributor to a large project, and you want to add a | |
2453 | complicated feature, and to present it to the other developers in a way | |
2454 | that makes it easy for them to read your changes, verify that they are | |
2455 | correct, and understand why you made each change. | |
2456 | ||
b181d57f | 2457 | If you present all of your changes as a single patch (or commit), they |
79c96c57 | 2458 | may find that it is too much to digest all at once. |
4c63ff45 BF |
2459 | |
2460 | If you present them with the entire history of your work, complete with | |
2461 | mistakes, corrections, and dead ends, they may be overwhelmed. | |
2462 | ||
2463 | So the ideal is usually to produce a series of patches such that: | |
2464 | ||
2465 | 1. Each patch can be applied in order. | |
2466 | ||
2467 | 2. Each patch includes a single logical change, together with a | |
2468 | message explaining the change. | |
2469 | ||
2470 | 3. No patch introduces a regression: after applying any initial | |
2471 | part of the series, the resulting project still compiles and | |
2472 | works, and has no bugs that it didn't have before. | |
2473 | ||
2474 | 4. The complete series produces the same end result as your own | |
2475 | (probably much messier!) development process did. | |
2476 | ||
b181d57f BF |
2477 | We will introduce some tools that can help you do this, explain how to |
2478 | use them, and then explain some of the problems that can arise because | |
2479 | you are rewriting history. | |
4c63ff45 | 2480 | |
e34caace | 2481 | [[using-git-rebase]] |
6127c086 | 2482 | Keeping a patch series up to date using git rebase |
4c63ff45 BF |
2483 | -------------------------------------------------- |
2484 | ||
1249d8ad TK |
2485 | Suppose that you create a branch `mywork` on a remote-tracking branch |
2486 | `origin`, and create some commits on top of it: | |
4c63ff45 BF |
2487 | |
2488 | ------------------------------------------------- | |
2489 | $ git checkout -b mywork origin | |
2490 | $ vi file.txt | |
2491 | $ git commit | |
2492 | $ vi otherfile.txt | |
2493 | $ git commit | |
2494 | ... | |
2495 | ------------------------------------------------- | |
2496 | ||
2497 | You have performed no merges into mywork, so it is just a simple linear | |
1249d8ad | 2498 | sequence of patches on top of `origin`: |
4c63ff45 | 2499 | |
1dc71a91 | 2500 | ................................................ |
fa8347b8 | 2501 | o--o--O <-- origin |
4c63ff45 | 2502 | \ |
fa8347b8 | 2503 | a--b--c <-- mywork |
1dc71a91 | 2504 | ................................................ |
4c63ff45 BF |
2505 | |
2506 | Some more interesting work has been done in the upstream project, and | |
1249d8ad | 2507 | `origin` has advanced: |
4c63ff45 | 2508 | |
1dc71a91 | 2509 | ................................................ |
4c63ff45 BF |
2510 | o--o--O--o--o--o <-- origin |
2511 | \ | |
2512 | a--b--c <-- mywork | |
1dc71a91 | 2513 | ................................................ |
4c63ff45 | 2514 | |
1249d8ad | 2515 | At this point, you could use `pull` to merge your changes back in; |
4c63ff45 BF |
2516 | the result would create a new merge commit, like this: |
2517 | ||
1dc71a91 | 2518 | ................................................ |
4c63ff45 BF |
2519 | o--o--O--o--o--o <-- origin |
2520 | \ \ | |
2521 | a--b--c--m <-- mywork | |
1dc71a91 | 2522 | ................................................ |
a6080a0a | 2523 | |
4c63ff45 BF |
2524 | However, if you prefer to keep the history in mywork a simple series of |
2525 | commits without any merges, you may instead choose to use | |
5162e697 | 2526 | linkgit:git-rebase[1]: |
4c63ff45 BF |
2527 | |
2528 | ------------------------------------------------- | |
2529 | $ git checkout mywork | |
2530 | $ git rebase origin | |
2531 | ------------------------------------------------- | |
2532 | ||
b181d57f | 2533 | This will remove each of your commits from mywork, temporarily saving |
1249d8ad | 2534 | them as patches (in a directory named `.git/rebase-apply`), update mywork to |
b181d57f BF |
2535 | point at the latest version of origin, then apply each of the saved |
2536 | patches to the new mywork. The result will look like: | |
4c63ff45 BF |
2537 | |
2538 | ||
1dc71a91 | 2539 | ................................................ |
4c63ff45 BF |
2540 | o--o--O--o--o--o <-- origin |
2541 | \ | |
2542 | a'--b'--c' <-- mywork | |
1dc71a91 | 2543 | ................................................ |
4c63ff45 | 2544 | |
b181d57f | 2545 | In the process, it may discover conflicts. In that case it will stop |
6127c086 | 2546 | and allow you to fix the conflicts; after fixing conflicts, use `git add` |
7a7d4ef6 | 2547 | to update the index with those contents, and then, instead of |
6127c086 | 2548 | running `git commit`, just run |
4c63ff45 BF |
2549 | |
2550 | ------------------------------------------------- | |
2551 | $ git rebase --continue | |
2552 | ------------------------------------------------- | |
2553 | ||
2de9b711 | 2554 | and Git will continue applying the rest of the patches. |
4c63ff45 | 2555 | |
b6cbca38 | 2556 | At any point you may use the `--abort` option to abort this process and |
4c63ff45 BF |
2557 | return mywork to the state it had before you started the rebase: |
2558 | ||
2559 | ------------------------------------------------- | |
2560 | $ git rebase --abort | |
2561 | ------------------------------------------------- | |
2562 | ||
6c26bf4d TK |
2563 | If you need to reorder or edit a number of commits in a branch, it may |
2564 | be easier to use `git rebase -i`, which allows you to reorder and | |
2565 | squash commits, as well as marking them for individual editing during | |
2566 | the rebase. See <<interactive-rebase>> for details, and | |
2567 | <<reordering-patch-series>> for alternatives. | |
2568 | ||
7cb192ea BF |
2569 | [[rewriting-one-commit]] |
2570 | Rewriting a single commit | |
365aa199 BF |
2571 | ------------------------- |
2572 | ||
7cb192ea | 2573 | We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the |
365aa199 BF |
2574 | most recent commit using |
2575 | ||
2576 | ------------------------------------------------- | |
2577 | $ git commit --amend | |
2578 | ------------------------------------------------- | |
2579 | ||
2580 | which will replace the old commit by a new commit incorporating your | |
2581 | changes, giving you a chance to edit the old commit message first. | |
6c26bf4d TK |
2582 | This is useful for fixing typos in your last commit, or for adjusting |
2583 | the patch contents of a poorly staged commit. | |
365aa199 | 2584 | |
6c26bf4d TK |
2585 | If you need to amend commits from deeper in your history, you can |
2586 | use <<interactive-rebase,interactive rebase's `edit` instruction>>. | |
365aa199 | 2587 | |
6c26bf4d TK |
2588 | [[reordering-patch-series]] |
2589 | Reordering or selecting from a patch series | |
2590 | ------------------------------------------- | |
365aa199 | 2591 | |
6c26bf4d TK |
2592 | Sometimes you want to edit a commit deeper in your history. One |
2593 | approach is to use `git format-patch` to create a series of patches | |
2594 | and then reset the state to before the patches: | |
365aa199 BF |
2595 | |
2596 | ------------------------------------------------- | |
6c26bf4d TK |
2597 | $ git format-patch origin |
2598 | $ git reset --hard origin | |
365aa199 BF |
2599 | ------------------------------------------------- |
2600 | ||
6c26bf4d TK |
2601 | Then modify, reorder, or eliminate patches as needed before applying |
2602 | them again with linkgit:git-am[1]: | |
365aa199 BF |
2603 | |
2604 | ------------------------------------------------- | |
6c26bf4d | 2605 | $ git am *.patch |
365aa199 BF |
2606 | ------------------------------------------------- |
2607 | ||
6c26bf4d TK |
2608 | [[interactive-rebase]] |
2609 | Using interactive rebases | |
2610 | ------------------------- | |
365aa199 | 2611 | |
6c26bf4d TK |
2612 | You can also edit a patch series with an interactive rebase. This is |
2613 | the same as <<reordering-patch-series,reordering a patch series using | |
2614 | `format-patch`>>, so use whichever interface you like best. | |
4c63ff45 | 2615 | |
6c26bf4d TK |
2616 | Rebase your current HEAD on the last commit you want to retain as-is. |
2617 | For example, if you want to reorder the last 5 commits, use: | |
b181d57f BF |
2618 | |
2619 | ------------------------------------------------- | |
6c26bf4d | 2620 | $ git rebase -i HEAD~5 |
b181d57f BF |
2621 | ------------------------------------------------- |
2622 | ||
6c26bf4d TK |
2623 | This will open your editor with a list of steps to be taken to perform |
2624 | your rebase. | |
4c63ff45 | 2625 | |
b181d57f | 2626 | ------------------------------------------------- |
6c26bf4d TK |
2627 | pick deadbee The oneline of this commit |
2628 | pick fa1afe1 The oneline of the next commit | |
2629 | ... | |
4c63ff45 | 2630 | |
6c26bf4d TK |
2631 | # Rebase c0ffeee..deadbee onto c0ffeee |
2632 | # | |
2633 | # Commands: | |
2634 | # p, pick = use commit | |
2635 | # r, reword = use commit, but edit the commit message | |
2636 | # e, edit = use commit, but stop for amending | |
2637 | # s, squash = use commit, but meld into previous commit | |
2638 | # f, fixup = like "squash", but discard this commit's log message | |
2639 | # x, exec = run command (the rest of the line) using shell | |
2640 | # | |
2641 | # These lines can be re-ordered; they are executed from top to bottom. | |
2642 | # | |
2643 | # If you remove a line here THAT COMMIT WILL BE LOST. | |
2644 | # | |
2645 | # However, if you remove everything, the rebase will be aborted. | |
2646 | # | |
2647 | # Note that empty commits are commented out | |
2648 | ------------------------------------------------- | |
2649 | ||
2650 | As explained in the comments, you can reorder commits, squash them | |
2651 | together, edit commit messages, etc. by editing the list. Once you | |
2652 | are satisfied, save the list and close your editor, and the rebase | |
2653 | will begin. | |
2654 | ||
2655 | The rebase will stop where `pick` has been replaced with `edit` or | |
2656 | when a step in the list fails to mechanically resolve conflicts and | |
2657 | needs your help. When you are done editing and/or resolving conflicts | |
2658 | you can continue with `git rebase --continue`. If you decide that | |
2659 | things are getting too hairy, you can always bail out with `git rebase | |
2660 | --abort`. Even after the rebase is complete, you can still recover | |
2661 | the original branch by using the <<reflogs,reflog>>. | |
2662 | ||
2663 | For a more detailed discussion of the procedure and additional tips, | |
2664 | see the "INTERACTIVE MODE" section of linkgit:git-rebase[1]. | |
4c63ff45 | 2665 | |
e34caace | 2666 | [[patch-series-tools]] |
4c63ff45 BF |
2667 | Other tools |
2668 | ----------- | |
2669 | ||
73a1d050 | 2670 | There are numerous other tools, such as StGit, which exist for the |
79c96c57 | 2671 | purpose of maintaining a patch series. These are outside of the scope of |
b181d57f | 2672 | this manual. |
4c63ff45 | 2673 | |
aa971cb9 | 2674 | [[problems-With-rewriting-history]] |
4c63ff45 BF |
2675 | Problems with rewriting history |
2676 | ------------------------------- | |
2677 | ||
b181d57f BF |
2678 | The primary problem with rewriting the history of a branch has to do |
2679 | with merging. Suppose somebody fetches your branch and merges it into | |
2680 | their branch, with a result something like this: | |
2681 | ||
1dc71a91 | 2682 | ................................................ |
b181d57f BF |
2683 | o--o--O--o--o--o <-- origin |
2684 | \ \ | |
2685 | t--t--t--m <-- their branch: | |
1dc71a91 | 2686 | ................................................ |
b181d57f BF |
2687 | |
2688 | Then suppose you modify the last three commits: | |
2689 | ||
1dc71a91 | 2690 | ................................................ |
b181d57f BF |
2691 | o--o--o <-- new head of origin |
2692 | / | |
2693 | o--o--O--o--o--o <-- old head of origin | |
1dc71a91 | 2694 | ................................................ |
b181d57f BF |
2695 | |
2696 | If we examined all this history together in one repository, it will | |
2697 | look like: | |
2698 | ||
1dc71a91 | 2699 | ................................................ |
b181d57f BF |
2700 | o--o--o <-- new head of origin |
2701 | / | |
2702 | o--o--O--o--o--o <-- old head of origin | |
2703 | \ \ | |
2704 | t--t--t--m <-- their branch: | |
1dc71a91 | 2705 | ................................................ |
b181d57f BF |
2706 | |
2707 | Git has no way of knowing that the new head is an updated version of | |
2708 | the old head; it treats this situation exactly the same as it would if | |
2709 | two developers had independently done the work on the old and new heads | |
2710 | in parallel. At this point, if someone attempts to merge the new head | |
2de9b711 | 2711 | in to their branch, Git will attempt to merge together the two (old and |
b181d57f BF |
2712 | new) lines of development, instead of trying to replace the old by the |
2713 | new. The results are likely to be unexpected. | |
2714 | ||
2715 | You may still choose to publish branches whose history is rewritten, | |
2716 | and it may be useful for others to be able to fetch those branches in | |
2717 | order to examine or test them, but they should not attempt to pull such | |
2718 | branches into their own work. | |
2719 | ||
2720 | For true distributed development that supports proper merging, | |
2721 | published branches should never be rewritten. | |
2722 | ||
3fb00282 SP |
2723 | [[bisect-merges]] |
2724 | Why bisecting merge commits can be harder than bisecting linear history | |
2725 | ----------------------------------------------------------------------- | |
2726 | ||
5162e697 | 2727 | The linkgit:git-bisect[1] command correctly handles history that |
3fb00282 SP |
2728 | includes merge commits. However, when the commit that it finds is a |
2729 | merge commit, the user may need to work harder than usual to figure out | |
2730 | why that commit introduced a problem. | |
2731 | ||
2732 | Imagine this history: | |
2733 | ||
2734 | ................................................ | |
2735 | ---Z---o---X---...---o---A---C---D | |
2736 | \ / | |
2737 | o---o---Y---...---o---B | |
2738 | ................................................ | |
2739 | ||
2740 | Suppose that on the upper line of development, the meaning of one | |
2741 | of the functions that exists at Z is changed at commit X. The | |
2742 | commits from Z leading to A change both the function's | |
2743 | implementation and all calling sites that exist at Z, as well | |
2744 | as new calling sites they add, to be consistent. There is no | |
2745 | bug at A. | |
2746 | ||
2747 | Suppose that in the meantime on the lower line of development somebody | |
2748 | adds a new calling site for that function at commit Y. The | |
2749 | commits from Z leading to B all assume the old semantics of that | |
2750 | function and the callers and the callee are consistent with each | |
2751 | other. There is no bug at B, either. | |
2752 | ||
2753 | Suppose further that the two development lines merge cleanly at C, | |
2754 | so no conflict resolution is required. | |
2755 | ||
2756 | Nevertheless, the code at C is broken, because the callers added | |
2757 | on the lower line of development have not been converted to the new | |
2758 | semantics introduced on the upper line of development. So if all | |
2759 | you know is that D is bad, that Z is good, and that | |
5162e697 | 2760 | linkgit:git-bisect[1] identifies C as the culprit, how will you |
3fb00282 SP |
2761 | figure out that the problem is due to this change in semantics? |
2762 | ||
6127c086 | 2763 | When the result of a `git bisect` is a non-merge commit, you should |
3fb00282 SP |
2764 | normally be able to discover the problem by examining just that commit. |
2765 | Developers can make this easy by breaking their changes into small | |
2766 | self-contained commits. That won't help in the case above, however, | |
2767 | because the problem isn't obvious from examination of any single | |
2768 | commit; instead, a global view of the development is required. To | |
2769 | make matters worse, the change in semantics in the problematic | |
2770 | function may be just one small part of the changes in the upper | |
2771 | line of development. | |
2772 | ||
2773 | On the other hand, if instead of merging at C you had rebased the | |
2774 | history between Z to B on top of A, you would have gotten this | |
2775 | linear history: | |
2776 | ||
2777 | ................................................................ | |
2778 | ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D* | |
2779 | ................................................................ | |
2780 | ||
2781 | Bisecting between Z and D* would hit a single culprit commit Y*, | |
2782 | and understanding why Y* was broken would probably be easier. | |
2783 | ||
2de9b711 | 2784 | Partly for this reason, many experienced Git users, even when |
3fb00282 SP |
2785 | working on an otherwise merge-heavy project, keep the history |
2786 | linear by rebasing against the latest upstream version before | |
2787 | publishing. | |
2788 | ||
e34caace | 2789 | [[advanced-branch-management]] |
b181d57f BF |
2790 | Advanced branch management |
2791 | ========================== | |
4c63ff45 | 2792 | |
e34caace | 2793 | [[fetching-individual-branches]] |
b181d57f BF |
2794 | Fetching individual branches |
2795 | ---------------------------- | |
2796 | ||
5162e697 | 2797 | Instead of using linkgit:git-remote[1], you can also choose just |
b181d57f BF |
2798 | to update one branch at a time, and to store it locally under an |
2799 | arbitrary name: | |
2800 | ||
2801 | ------------------------------------------------- | |
2802 | $ git fetch origin todo:my-todo-work | |
2803 | ------------------------------------------------- | |
2804 | ||
1249d8ad | 2805 | The first argument, `origin`, just tells Git to fetch from the |
2de9b711 | 2806 | repository you originally cloned from. The second argument tells Git |
1249d8ad TK |
2807 | to fetch the branch named `todo` from the remote repository, and to |
2808 | store it locally under the name `refs/heads/my-todo-work`. | |
b181d57f BF |
2809 | |
2810 | You can also fetch branches from other repositories; so | |
2811 | ||
2812 | ------------------------------------------------- | |
2813 | $ git fetch git://example.com/proj.git master:example-master | |
2814 | ------------------------------------------------- | |
2815 | ||
1249d8ad TK |
2816 | will create a new branch named `example-master` and store in it the |
2817 | branch named `master` from the repository at the given URL. If you | |
b181d57f | 2818 | already have a branch named example-master, it will attempt to |
59723040 BF |
2819 | <<fast-forwards,fast-forward>> to the commit given by example.com's |
2820 | master branch. In more detail: | |
b181d57f | 2821 | |
59723040 BF |
2822 | [[fetch-fast-forwards]] |
2823 | git fetch and fast-forwards | |
2824 | --------------------------- | |
b181d57f | 2825 | |
1249d8ad | 2826 | In the previous example, when updating an existing branch, `git fetch` |
7a7d4ef6 | 2827 | checks to make sure that the most recent commit on the remote |
b181d57f BF |
2828 | branch is a descendant of the most recent commit on your copy of the |
2829 | branch before updating your copy of the branch to point at the new | |
a75d7b54 | 2830 | commit. Git calls this process a <<fast-forwards,fast-forward>>. |
b181d57f | 2831 | |
a75d7b54 | 2832 | A fast-forward looks something like this: |
b181d57f | 2833 | |
1dc71a91 | 2834 | ................................................ |
b181d57f BF |
2835 | o--o--o--o <-- old head of the branch |
2836 | \ | |
2837 | o--o--o <-- new head of the branch | |
1dc71a91 | 2838 | ................................................ |
b181d57f BF |
2839 | |
2840 | ||
2841 | In some cases it is possible that the new head will *not* actually be | |
2842 | a descendant of the old head. For example, the developer may have | |
2843 | realized she made a serious mistake, and decided to backtrack, | |
2844 | resulting in a situation like: | |
2845 | ||
1dc71a91 | 2846 | ................................................ |
b181d57f BF |
2847 | o--o--o--o--a--b <-- old head of the branch |
2848 | \ | |
2849 | o--o--o <-- new head of the branch | |
1dc71a91 | 2850 | ................................................ |
b181d57f | 2851 | |
1249d8ad | 2852 | In this case, `git fetch` will fail, and print out a warning. |
b181d57f | 2853 | |
2de9b711 | 2854 | In that case, you can still force Git to update to the new head, as |
b181d57f | 2855 | described in the following section. However, note that in the |
1249d8ad | 2856 | situation above this may mean losing the commits labeled `a` and `b`, |
b181d57f BF |
2857 | unless you've already created a reference of your own pointing to |
2858 | them. | |
2859 | ||
e34caace | 2860 | [[forcing-fetch]] |
6127c086 | 2861 | Forcing git fetch to do non-fast-forward updates |
b181d57f BF |
2862 | ------------------------------------------------ |
2863 | ||
2864 | If git fetch fails because the new head of a branch is not a | |
2865 | descendant of the old head, you may force the update with: | |
2866 | ||
2867 | ------------------------------------------------- | |
2868 | $ git fetch git://example.com/proj.git +master:refs/remotes/example/master | |
2869 | ------------------------------------------------- | |
2870 | ||
1249d8ad | 2871 | Note the addition of the `+` sign. Alternatively, you can use the `-f` |
c64415e2 BF |
2872 | flag to force updates of all the fetched branches, as in: |
2873 | ||
2874 | ------------------------------------------------- | |
2875 | $ git fetch -f origin | |
2876 | ------------------------------------------------- | |
2877 | ||
2878 | Be aware that commits that the old version of example/master pointed at | |
2879 | may be lost, as we saw in the previous section. | |
b181d57f | 2880 | |
e34caace | 2881 | [[remote-branch-configuration]] |
29b9a66f MM |
2882 | Configuring remote-tracking branches |
2883 | ------------------------------------ | |
b181d57f | 2884 | |
1249d8ad | 2885 | We saw above that `origin` is just a shortcut to refer to the |
79c96c57 | 2886 | repository that you originally cloned from. This information is |
2de9b711 | 2887 | stored in Git configuration variables, which you can see using |
5162e697 | 2888 | linkgit:git-config[1]: |
b181d57f BF |
2889 | |
2890 | ------------------------------------------------- | |
9d13bda3 | 2891 | $ git config -l |
b181d57f BF |
2892 | core.repositoryformatversion=0 |
2893 | core.filemode=true | |
2894 | core.logallrefupdates=true | |
2895 | remote.origin.url=git://git.kernel.org/pub/scm/git/git.git | |
2896 | remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* | |
2897 | branch.master.remote=origin | |
2898 | branch.master.merge=refs/heads/master | |
2899 | ------------------------------------------------- | |
2900 | ||
2901 | If there are other repositories that you also use frequently, you can | |
2902 | create similar configuration options to save typing; for example, | |
b181d57f BF |
2903 | |
2904 | ------------------------------------------------- | |
47adb8ac | 2905 | $ git remote add example git://example.com/proj.git |
b181d57f BF |
2906 | ------------------------------------------------- |
2907 | ||
47adb8ac | 2908 | adds the following to `.git/config`: |
b181d57f BF |
2909 | |
2910 | ------------------------------------------------- | |
47adb8ac TK |
2911 | [remote "example"] |
2912 | url = git://example.com/proj.git | |
2913 | fetch = +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2914 | ------------------------------------------------- |
2915 | ||
47adb8ac TK |
2916 | Also note that the above configuration can be performed by directly |
2917 | editing the file `.git/config` instead of using linkgit:git-remote[1]. | |
b181d57f | 2918 | |
47adb8ac TK |
2919 | After configuring the remote, the following three commands will do the |
2920 | same thing: | |
b181d57f BF |
2921 | |
2922 | ------------------------------------------------- | |
47adb8ac TK |
2923 | $ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/* |
2924 | $ git fetch example +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2925 | $ git fetch example |
2926 | ------------------------------------------------- | |
2927 | ||
5162e697 | 2928 | See linkgit:git-config[1] for more details on the configuration |
47adb8ac TK |
2929 | options mentioned above and linkgit:git-fetch[1] for more details on |
2930 | the refspec syntax. | |
d19fbc3c | 2931 | |
d19fbc3c | 2932 | |
036f8199 BF |
2933 | [[git-concepts]] |
2934 | Git concepts | |
2935 | ============ | |
d19fbc3c | 2936 | |
036f8199 BF |
2937 | Git is built on a small number of simple but powerful ideas. While it |
2938 | is possible to get things done without understanding them, you will find | |
2de9b711 | 2939 | Git much more intuitive if you do. |
036f8199 BF |
2940 | |
2941 | We start with the most important, the <<def_object_database,object | |
2942 | database>> and the <<def_index,index>>. | |
b181d57f | 2943 | |
e34caace | 2944 | [[the-object-database]] |
b181d57f BF |
2945 | The Object Database |
2946 | ------------------- | |
2947 | ||
1bbf1c79 BF |
2948 | |
2949 | We already saw in <<understanding-commits>> that all commits are stored | |
2950 | under a 40-digit "object name". In fact, all the information needed to | |
2951 | represent the history of a project is stored in objects with such names. | |
a6e5ef7d FC |
2952 | In each case the name is calculated by taking the SHA-1 hash of the |
2953 | contents of the object. The SHA-1 hash is a cryptographic hash function. | |
1bbf1c79 BF |
2954 | What that means to us is that it is impossible to find two different |
2955 | objects with the same name. This has a number of advantages; among | |
2956 | others: | |
2957 | ||
2958 | - Git can quickly determine whether two objects are identical or not, | |
2959 | just by comparing names. | |
06ada152 | 2960 | - Since object names are computed the same way in every repository, the |
1bbf1c79 BF |
2961 | same content stored in two repositories will always be stored under |
2962 | the same name. | |
2963 | - Git can detect errors when it reads an object, by checking that the | |
a6e5ef7d | 2964 | object's name is still the SHA-1 hash of its contents. |
1bbf1c79 BF |
2965 | |
2966 | (See <<object-details>> for the details of the object formatting and | |
a6e5ef7d | 2967 | SHA-1 calculation.) |
1bbf1c79 BF |
2968 | |
2969 | There are four different types of objects: "blob", "tree", "commit", and | |
2970 | "tag". | |
2971 | ||
2972 | - A <<def_blob_object,"blob" object>> is used to store file data. | |
843c81dc | 2973 | - A <<def_tree_object,"tree" object>> ties one or more |
1bbf1c79 BF |
2974 | "blob" objects into a directory structure. In addition, a tree object |
2975 | can refer to other tree objects, thus creating a directory hierarchy. | |
2976 | - A <<def_commit_object,"commit" object>> ties such directory hierarchies | |
2ef8ac1b | 2977 | together into a <<def_DAG,directed acyclic graph>> of revisions--each |
1bbf1c79 BF |
2978 | commit contains the object name of exactly one tree designating the |
2979 | directory hierarchy at the time of the commit. In addition, a commit | |
2980 | refers to "parent" commit objects that describe the history of how we | |
2981 | arrived at that directory hierarchy. | |
2982 | - A <<def_tag_object,"tag" object>> symbolically identifies and can be | |
2983 | used to sign other objects. It contains the object name and type of | |
2984 | another object, a symbolic name (of course!) and, optionally, a | |
2985 | signature. | |
b181d57f | 2986 | |
b181d57f BF |
2987 | The object types in some more detail: |
2988 | ||
513d419c BF |
2989 | [[commit-object]] |
2990 | Commit Object | |
2991 | ~~~~~~~~~~~~~ | |
b181d57f | 2992 | |
1bbf1c79 | 2993 | The "commit" object links a physical state of a tree with a description |
1249d8ad | 2994 | of how we got there and why. Use the `--pretty=raw` option to |
5162e697 | 2995 | linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite |
1bbf1c79 BF |
2996 | commit: |
2997 | ||
2998 | ------------------------------------------------ | |
2999 | $ git show -s --pretty=raw 2be7fcb476 | |
3000 | commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4 | |
3001 | tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf | |
3002 | parent 257a84d9d02e90447b149af58b271c19405edb6a | |
3003 | author Dave Watson <dwatson@mimvista.com> 1187576872 -0400 | |
3004 | committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700 | |
3005 | ||
3006 | Fix misspelling of 'suppress' in docs | |
3007 | ||
3008 | Signed-off-by: Junio C Hamano <gitster@pobox.com> | |
3009 | ------------------------------------------------ | |
3010 | ||
3011 | As you can see, a commit is defined by: | |
3012 | ||
a6e5ef7d | 3013 | - a tree: The SHA-1 name of a tree object (as defined below), representing |
1bbf1c79 | 3014 | the contents of a directory at a certain point in time. |
edfbbf7e | 3015 | - parent(s): The SHA-1 name(s) of some number of commits which represent the |
9e5d87d4 | 3016 | immediately previous step(s) in the history of the project. The |
1bbf1c79 BF |
3017 | example above has one parent; merge commits may have more than |
3018 | one. A commit with no parents is called a "root" commit, and | |
3019 | represents the initial revision of a project. Each project must have | |
3020 | at least one root. A project can also have multiple roots, though | |
3021 | that isn't common (or necessarily a good idea). | |
3022 | - an author: The name of the person responsible for this change, together | |
3023 | with its date. | |
3024 | - a committer: The name of the person who actually created the commit, | |
3025 | with the date it was done. This may be different from the author, for | |
3026 | example, if the author was someone who wrote a patch and emailed it | |
3027 | to the person who used it to create the commit. | |
3028 | - a comment describing this commit. | |
3029 | ||
3030 | Note that a commit does not itself contain any information about what | |
3031 | actually changed; all changes are calculated by comparing the contents | |
3032 | of the tree referred to by this commit with the trees associated with | |
2de9b711 | 3033 | its parents. In particular, Git does not attempt to record file renames |
1bbf1c79 BF |
3034 | explicitly, though it can identify cases where the existence of the same |
3035 | file data at changing paths suggests a rename. (See, for example, the | |
1249d8ad | 3036 | `-M` option to linkgit:git-diff[1]). |
1bbf1c79 | 3037 | |
5162e697 | 3038 | A commit is usually created by linkgit:git-commit[1], which creates a |
1bbf1c79 BF |
3039 | commit whose parent is normally the current HEAD, and whose tree is |
3040 | taken from the content currently stored in the index. | |
b181d57f | 3041 | |
e34caace | 3042 | [[tree-object]] |
b181d57f | 3043 | Tree Object |
971aa71f | 3044 | ~~~~~~~~~~~ |
b181d57f | 3045 | |
5162e697 DM |
3046 | The ever-versatile linkgit:git-show[1] command can also be used to |
3047 | examine tree objects, but linkgit:git-ls-tree[1] will give you more | |
1bbf1c79 BF |
3048 | details: |
3049 | ||
3050 | ------------------------------------------------ | |
3051 | $ git ls-tree fb3a8bdd0ce | |
3052 | 100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore | |
3053 | 100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap | |
3054 | 100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING | |
3055 | 040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation | |
3056 | 100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN | |
3057 | 100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL | |
3058 | 100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile | |
3059 | 100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README | |
3060 | ... | |
3061 | ------------------------------------------------ | |
3062 | ||
3063 | As you can see, a tree object contains a list of entries, each with a | |
a6e5ef7d | 3064 | mode, object type, SHA-1 name, and name, sorted by name. It represents |
1bbf1c79 BF |
3065 | the contents of a single directory tree. |
3066 | ||
3067 | The object type may be a blob, representing the contents of a file, or | |
3068 | another tree, representing the contents of a subdirectory. Since trees | |
a6e5ef7d FC |
3069 | and blobs, like all other objects, are named by the SHA-1 hash of their |
3070 | contents, two trees have the same SHA-1 name if and only if their | |
1bbf1c79 | 3071 | contents (including, recursively, the contents of all subdirectories) |
2de9b711 | 3072 | are identical. This allows Git to quickly determine the differences |
1bbf1c79 BF |
3073 | between two related tree objects, since it can ignore any entries with |
3074 | identical object names. | |
3075 | ||
3076 | (Note: in the presence of submodules, trees may also have commits as | |
6dd14366 | 3077 | entries. See <<submodules>> for documentation.) |
1bbf1c79 | 3078 | |
2de9b711 | 3079 | Note that the files all have mode 644 or 755: Git actually only pays |
1bbf1c79 | 3080 | attention to the executable bit. |
b181d57f | 3081 | |
513d419c BF |
3082 | [[blob-object]] |
3083 | Blob Object | |
3084 | ~~~~~~~~~~~ | |
b181d57f | 3085 | |
5162e697 | 3086 | You can use linkgit:git-show[1] to examine the contents of a blob; take, |
1249d8ad | 3087 | for example, the blob in the entry for `COPYING` from the tree above: |
b181d57f | 3088 | |
1bbf1c79 BF |
3089 | ------------------------------------------------ |
3090 | $ git show 6ff87c4664 | |
3091 | ||
3092 | Note that the only valid version of the GPL as far as this project | |
3093 | is concerned is _this_ particular version of the license (ie v2, not | |
3094 | v2.2 or v3.x or whatever), unless explicitly otherwise stated. | |
3095 | ... | |
3096 | ------------------------------------------------ | |
b181d57f | 3097 | |
1bbf1c79 BF |
3098 | A "blob" object is nothing but a binary blob of data. It doesn't refer |
3099 | to anything else or have attributes of any kind. | |
3100 | ||
3101 | Since the blob is entirely defined by its data, if two files in a | |
3102 | directory tree (or in multiple different versions of the repository) | |
3103 | have the same contents, they will share the same blob object. The object | |
3104 | is totally independent of its location in the directory tree, and | |
3105 | renaming a file does not change the object that file is associated with. | |
3106 | ||
3107 | Note that any tree or blob object can be examined using | |
5162e697 | 3108 | linkgit:git-show[1] with the <revision>:<path> syntax. This can |
1bbf1c79 BF |
3109 | sometimes be useful for browsing the contents of a tree that is not |
3110 | currently checked out. | |
b181d57f | 3111 | |
e34caace | 3112 | [[trust]] |
b181d57f | 3113 | Trust |
971aa71f | 3114 | ~~~~~ |
b181d57f | 3115 | |
a6e5ef7d | 3116 | If you receive the SHA-1 name of a blob from one source, and its contents |
1bbf1c79 | 3117 | from another (possibly untrusted) source, you can still trust that those |
a6e5ef7d FC |
3118 | contents are correct as long as the SHA-1 name agrees. This is because |
3119 | the SHA-1 is designed so that it is infeasible to find different contents | |
1bbf1c79 | 3120 | that produce the same hash. |
b181d57f | 3121 | |
a6e5ef7d | 3122 | Similarly, you need only trust the SHA-1 name of a top-level tree object |
1bbf1c79 | 3123 | to trust the contents of the entire directory that it refers to, and if |
a6e5ef7d | 3124 | you receive the SHA-1 name of a commit from a trusted source, then you |
1bbf1c79 BF |
3125 | can easily verify the entire history of commits reachable through |
3126 | parents of that commit, and all of those contents of the trees referred | |
3127 | to by those commits. | |
b181d57f BF |
3128 | |
3129 | So to introduce some real trust in the system, the only thing you need | |
3130 | to do is to digitally sign just 'one' special note, which includes the | |
3131 | name of a top-level commit. Your digital signature shows others | |
3132 | that you trust that commit, and the immutability of the history of | |
3133 | commits tells others that they can trust the whole history. | |
3134 | ||
3135 | In other words, you can easily validate a whole archive by just | |
a6e5ef7d | 3136 | sending out a single email that tells the people the name (SHA-1 hash) |
b181d57f BF |
3137 | of the top commit, and digitally sign that email using something |
3138 | like GPG/PGP. | |
3139 | ||
2de9b711 | 3140 | To assist in this, Git also provides the tag object... |
b181d57f | 3141 | |
e34caace | 3142 | [[tag-object]] |
b181d57f | 3143 | Tag Object |
971aa71f | 3144 | ~~~~~~~~~~ |
b181d57f | 3145 | |
1bbf1c79 BF |
3146 | A tag object contains an object, object type, tag name, the name of the |
3147 | person ("tagger") who created the tag, and a message, which may contain | |
843c81dc | 3148 | a signature, as can be seen using linkgit:git-cat-file[1]: |
b181d57f | 3149 | |
1bbf1c79 BF |
3150 | ------------------------------------------------ |
3151 | $ git cat-file tag v1.5.0 | |
3152 | object 437b1b20df4b356c9342dac8d38849f24ef44f27 | |
3153 | type commit | |
3154 | tag v1.5.0 | |
3155 | tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000 | |
3156 | ||
3157 | GIT 1.5.0 | |
3158 | -----BEGIN PGP SIGNATURE----- | |
3159 | Version: GnuPG v1.4.6 (GNU/Linux) | |
3160 | ||
3161 | iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui | |
3162 | nLE/L9aUXdWeTFPron96DLA= | |
3163 | =2E+0 | |
3164 | -----END PGP SIGNATURE----- | |
3165 | ------------------------------------------------ | |
b181d57f | 3166 | |
5162e697 DM |
3167 | See the linkgit:git-tag[1] command to learn how to create and verify tag |
3168 | objects. (Note that linkgit:git-tag[1] can also be used to create | |
1bbf1c79 | 3169 | "lightweight tags", which are not tag objects at all, but just simple |
1249d8ad | 3170 | references whose names begin with `refs/tags/`). |
b181d57f | 3171 | |
09eff7b0 | 3172 | [[pack-files]] |
2de9b711 | 3173 | How Git stores objects efficiently: pack files |
09eff7b0 BF |
3174 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
3175 | ||
9644ffdd | 3176 | Newly created objects are initially created in a file named after the |
1249d8ad | 3177 | object's SHA-1 hash (stored in `.git/objects`). |
09eff7b0 BF |
3178 | |
3179 | Unfortunately this system becomes inefficient once a project has a | |
3180 | lot of objects. Try this on an old project: | |
3181 | ||
3182 | ------------------------------------------------ | |
3183 | $ git count-objects | |
3184 | 6930 objects, 47620 kilobytes | |
3185 | ------------------------------------------------ | |
3186 | ||
3187 | The first number is the number of objects which are kept in | |
3188 | individual files. The second is the amount of space taken up by | |
3189 | those "loose" objects. | |
3190 | ||
2de9b711 | 3191 | You can save space and make Git faster by moving these loose objects in |
09eff7b0 BF |
3192 | to a "pack file", which stores a group of objects in an efficient |
3193 | compressed format; the details of how pack files are formatted can be | |
3194 | found in link:technical/pack-format.txt[technical/pack-format.txt]. | |
3195 | ||
3196 | To put the loose objects into a pack, just run git repack: | |
3197 | ||
3198 | ------------------------------------------------ | |
3199 | $ git repack | |
3200 | Generating pack... | |
3201 | Done counting 6020 objects. | |
3202 | Deltifying 6020 objects. | |
3203 | 100% (6020/6020) done | |
3204 | Writing 6020 objects. | |
3205 | 100% (6020/6020) done | |
3206 | Total 6020, written 6020 (delta 4070), reused 0 (delta 0) | |
3207 | Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created. | |
3208 | ------------------------------------------------ | |
3209 | ||
3210 | You can then run | |
3211 | ||
3212 | ------------------------------------------------ | |
3213 | $ git prune | |
3214 | ------------------------------------------------ | |
3215 | ||
3216 | to remove any of the "loose" objects that are now contained in the | |
3217 | pack. This will also remove any unreferenced objects (which may be | |
1249d8ad | 3218 | created when, for example, you use `git reset` to remove a commit). |
09eff7b0 | 3219 | You can verify that the loose objects are gone by looking at the |
1249d8ad | 3220 | `.git/objects` directory or by running |
09eff7b0 BF |
3221 | |
3222 | ------------------------------------------------ | |
3223 | $ git count-objects | |
3224 | 0 objects, 0 kilobytes | |
3225 | ------------------------------------------------ | |
3226 | ||
3227 | Although the object files are gone, any commands that refer to those | |
3228 | objects will work exactly as they did before. | |
3229 | ||
5162e697 | 3230 | The linkgit:git-gc[1] command performs packing, pruning, and more for |
09eff7b0 BF |
3231 | you, so is normally the only high-level command you need. |
3232 | ||
3233 | [[dangling-objects]] | |
3234 | Dangling objects | |
3235 | ~~~~~~~~~~~~~~~~ | |
3236 | ||
5162e697 | 3237 | The linkgit:git-fsck[1] command will sometimes complain about dangling |
09eff7b0 BF |
3238 | objects. They are not a problem. |
3239 | ||
3240 | The most common cause of dangling objects is that you've rebased a | |
3241 | branch, or you have pulled from somebody else who rebased a branch--see | |
3242 | <<cleaning-up-history>>. In that case, the old head of the original | |
3243 | branch still exists, as does everything it pointed to. The branch | |
3244 | pointer itself just doesn't, since you replaced it with another one. | |
3245 | ||
3246 | There are also other situations that cause dangling objects. For | |
1249d8ad | 3247 | example, a "dangling blob" may arise because you did a `git add` of a |
09eff7b0 BF |
3248 | file, but then, before you actually committed it and made it part of the |
3249 | bigger picture, you changed something else in that file and committed | |
2ef8ac1b | 3250 | that *updated* thing--the old state that you added originally ends up |
09eff7b0 BF |
3251 | not being pointed to by any commit or tree, so it's now a dangling blob |
3252 | object. | |
3253 | ||
3254 | Similarly, when the "recursive" merge strategy runs, and finds that | |
3255 | there are criss-cross merges and thus more than one merge base (which is | |
3256 | fairly unusual, but it does happen), it will generate one temporary | |
3257 | midway tree (or possibly even more, if you had lots of criss-crossing | |
3258 | merges and more than two merge bases) as a temporary internal merge | |
3259 | base, and again, those are real objects, but the end result will not end | |
3260 | up pointing to them, so they end up "dangling" in your repository. | |
3261 | ||
3262 | Generally, dangling objects aren't anything to worry about. They can | |
3263 | even be very useful: if you screw something up, the dangling objects can | |
3264 | be how you recover your old tree (say, you did a rebase, and realized | |
2ef8ac1b | 3265 | that you really didn't want to--you can look at what dangling objects |
09eff7b0 BF |
3266 | you have, and decide to reset your head to some old dangling state). |
3267 | ||
3268 | For commits, you can just use: | |
3269 | ||
3270 | ------------------------------------------------ | |
3271 | $ gitk <dangling-commit-sha-goes-here> --not --all | |
3272 | ------------------------------------------------ | |
3273 | ||
3274 | This asks for all the history reachable from the given commit but not | |
3275 | from any branch, tag, or other reference. If you decide it's something | |
3276 | you want, you can always create a new reference to it, e.g., | |
3277 | ||
3278 | ------------------------------------------------ | |
3279 | $ git branch recovered-branch <dangling-commit-sha-goes-here> | |
3280 | ------------------------------------------------ | |
3281 | ||
3282 | For blobs and trees, you can't do the same, but you can still examine | |
3283 | them. You can just do | |
3284 | ||
3285 | ------------------------------------------------ | |
3286 | $ git show <dangling-blob/tree-sha-goes-here> | |
3287 | ------------------------------------------------ | |
3288 | ||
3289 | to show what the contents of the blob were (or, for a tree, basically | |
1249d8ad | 3290 | what the `ls` for that directory was), and that may give you some idea |
09eff7b0 BF |
3291 | of what the operation was that left that dangling object. |
3292 | ||
3293 | Usually, dangling blobs and trees aren't very interesting. They're | |
3294 | almost always the result of either being a half-way mergebase (the blob | |
3295 | will often even have the conflict markers from a merge in it, if you | |
3296 | have had conflicting merges that you fixed up by hand), or simply | |
1249d8ad | 3297 | because you interrupted a `git fetch` with ^C or something like that, |
09eff7b0 BF |
3298 | leaving _some_ of the new objects in the object database, but just |
3299 | dangling and useless. | |
3300 | ||
3301 | Anyway, once you are sure that you're not interested in any dangling | |
3302 | state, you can just prune all unreachable objects: | |
3303 | ||
3304 | ------------------------------------------------ | |
3305 | $ git prune | |
3306 | ------------------------------------------------ | |
3307 | ||
1249d8ad | 3308 | and they'll be gone. But you should only run `git prune` on a quiescent |
2ef8ac1b | 3309 | repository--it's kind of like doing a filesystem fsck recovery: you |
09eff7b0 BF |
3310 | don't want to do that while the filesystem is mounted. |
3311 | ||
1249d8ad | 3312 | (The same is true of `git fsck` itself, btw, but since |
6127c086 FC |
3313 | `git fsck` never actually *changes* the repository, it just reports |
3314 | on what it found, `git fsck` itself is never 'dangerous' to run. | |
09eff7b0 BF |
3315 | Running it while somebody is actually changing the repository can cause |
3316 | confusing and scary messages, but it won't actually do anything bad. In | |
1249d8ad | 3317 | contrast, running `git prune` while somebody is actively changing the |
09eff7b0 | 3318 | repository is a *BAD* idea). |
b181d57f | 3319 | |
1cdade2c BF |
3320 | [[recovering-from-repository-corruption]] |
3321 | Recovering from repository corruption | |
3322 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3323 | ||
2de9b711 TA |
3324 | By design, Git treats data trusted to it with caution. However, even in |
3325 | the absence of bugs in Git itself, it is still possible that hardware or | |
1cdade2c BF |
3326 | operating system errors could corrupt data. |
3327 | ||
3328 | The first defense against such problems is backups. You can back up a | |
2de9b711 | 3329 | Git directory using clone, or just using cp, tar, or any other backup |
1cdade2c BF |
3330 | mechanism. |
3331 | ||
3332 | As a last resort, you can search for the corrupted objects and attempt | |
3333 | to replace them by hand. Back up your repository before attempting this | |
3334 | in case you corrupt things even more in the process. | |
3335 | ||
3336 | We'll assume that the problem is a single missing or corrupted blob, | |
9e5d87d4 | 3337 | which is sometimes a solvable problem. (Recovering missing trees and |
1cdade2c BF |
3338 | especially commits is *much* harder). |
3339 | ||
3340 | Before starting, verify that there is corruption, and figure out where | |
5162e697 | 3341 | it is with linkgit:git-fsck[1]; this may be time-consuming. |
1cdade2c BF |
3342 | |
3343 | Assume the output looks like this: | |
3344 | ||
3345 | ------------------------------------------------ | |
c6a13b2c | 3346 | $ git fsck --full --no-dangling |
1cdade2c BF |
3347 | broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 |
3348 | to blob 4b9458b3786228369c63936db65827de3cc06200 | |
3349 | missing blob 4b9458b3786228369c63936db65827de3cc06200 | |
3350 | ------------------------------------------------ | |
3351 | ||
1cdade2c BF |
3352 | Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6 |
3353 | points to it. If you could find just one copy of that missing blob | |
3354 | object, possibly in some other repository, you could move it into | |
1249d8ad | 3355 | `.git/objects/4b/9458b3...` and be done. Suppose you can't. You can |
5162e697 | 3356 | still examine the tree that pointed to it with linkgit:git-ls-tree[1], |
1cdade2c BF |
3357 | which might output something like: |
3358 | ||
3359 | ------------------------------------------------ | |
3360 | $ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 | |
3361 | 100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore | |
3362 | 100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap | |
3363 | 100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING | |
3364 | ... | |
3365 | 100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile | |
3366 | ... | |
3367 | ------------------------------------------------ | |
3368 | ||
3369 | So now you know that the missing blob was the data for a file named | |
1249d8ad TK |
3370 | `myfile`. And chances are you can also identify the directory--let's |
3371 | say it's in `somedirectory`. If you're lucky the missing copy might be | |
1cdade2c | 3372 | the same as the copy you have checked out in your working tree at |
1249d8ad | 3373 | `somedirectory/myfile`; you can test whether that's right with |
5162e697 | 3374 | linkgit:git-hash-object[1]: |
1cdade2c BF |
3375 | |
3376 | ------------------------------------------------ | |
3377 | $ git hash-object -w somedirectory/myfile | |
3378 | ------------------------------------------------ | |
3379 | ||
3380 | which will create and store a blob object with the contents of | |
a6e5ef7d | 3381 | somedirectory/myfile, and output the SHA-1 of that object. if you're |
1cdade2c BF |
3382 | extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in |
3383 | which case you've guessed right, and the corruption is fixed! | |
3384 | ||
3385 | Otherwise, you need more information. How do you tell which version of | |
3386 | the file has been lost? | |
3387 | ||
3388 | The easiest way to do this is with: | |
3389 | ||
3390 | ------------------------------------------------ | |
3391 | $ git log --raw --all --full-history -- somedirectory/myfile | |
3392 | ------------------------------------------------ | |
3393 | ||
3394 | Because you're asking for raw output, you'll now get something like | |
3395 | ||
3396 | ------------------------------------------------ | |
3397 | commit abc | |
3398 | Author: | |
3399 | Date: | |
3400 | ... | |
3401 | :100644 100644 4b9458b... newsha... M somedirectory/myfile | |
3402 | ||
3403 | ||
3404 | commit xyz | |
3405 | Author: | |
3406 | Date: | |
3407 | ||
3408 | ... | |
3409 | :100644 100644 oldsha... 4b9458b... M somedirectory/myfile | |
3410 | ------------------------------------------------ | |
3411 | ||
edfbbf7e ŠN |
3412 | This tells you that the immediately following version of the file was |
3413 | "newsha", and that the immediately preceding version was "oldsha". | |
1cdade2c BF |
3414 | You also know the commit messages that went with the change from oldsha |
3415 | to 4b9458b and with the change from 4b9458b to newsha. | |
3416 | ||
3417 | If you've been committing small enough changes, you may now have a good | |
3418 | shot at reconstructing the contents of the in-between state 4b9458b. | |
3419 | ||
3420 | If you can do that, you can now recreate the missing object with | |
3421 | ||
3422 | ------------------------------------------------ | |
3423 | $ git hash-object -w <recreated-file> | |
3424 | ------------------------------------------------ | |
3425 | ||
3426 | and your repository is good again! | |
3427 | ||
1249d8ad | 3428 | (Btw, you could have ignored the `fsck`, and started with doing a |
1cdade2c BF |
3429 | |
3430 | ------------------------------------------------ | |
3431 | $ git log --raw --all | |
3432 | ------------------------------------------------ | |
3433 | ||
1ab58e8d | 3434 | and just looked for the sha of the missing object (4b9458b..) in that |
da2c7b3d | 3435 | whole thing. It's up to you--Git does *have* a lot of information, it is |
1cdade2c BF |
3436 | just missing one particular blob version. |
3437 | ||
e34caace | 3438 | [[the-index]] |
1c097891 BF |
3439 | The index |
3440 | ----------- | |
3441 | ||
1249d8ad | 3442 | The index is a binary file (generally kept in `.git/index`) containing a |
a6e5ef7d | 3443 | sorted list of path names, each with permissions and the SHA-1 of a blob |
5162e697 | 3444 | object; linkgit:git-ls-files[1] can show you the contents of the index: |
b181d57f | 3445 | |
1c097891 BF |
3446 | ------------------------------------------------- |
3447 | $ git ls-files --stage | |
3448 | 100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore | |
3449 | 100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap | |
3450 | 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING | |
3451 | 100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore | |
3452 | 100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile | |
3453 | ... | |
3454 | 100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h | |
3455 | 100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c | |
3456 | 100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h | |
3457 | ------------------------------------------------- | |
3458 | ||
3459 | Note that in older documentation you may see the index called the | |
3460 | "current directory cache" or just the "cache". It has three important | |
3461 | properties: | |
3462 | ||
3463 | 1. The index contains all the information necessary to generate a single | |
3464 | (uniquely determined) tree object. | |
3465 | + | |
5162e697 | 3466 | For example, running linkgit:git-commit[1] generates this tree object |
1c097891 BF |
3467 | from the index, stores it in the object database, and uses it as the |
3468 | tree object associated with the new commit. | |
3469 | ||
3470 | 2. The index enables fast comparisons between the tree object it defines | |
3471 | and the working tree. | |
3472 | + | |
3473 | It does this by storing some additional data for each entry (such as | |
3474 | the last modified time). This data is not displayed above, and is not | |
3475 | stored in the created tree object, but it can be used to determine | |
3476 | quickly which files in the working directory differ from what was | |
2de9b711 | 3477 | stored in the index, and thus save Git from having to read all of the |
1c097891 BF |
3478 | data from such files to look for changes. |
3479 | ||
3480 | 3. It can efficiently represent information about merge conflicts | |
3481 | between different tree objects, allowing each pathname to be | |
b181d57f | 3482 | associated with sufficient information about the trees involved that |
1c097891 BF |
3483 | you can create a three-way merge between them. |
3484 | + | |
3485 | We saw in <<conflict-resolution>> that during a merge the index can | |
3486 | store multiple versions of a single file (called "stages"). The third | |
5162e697 | 3487 | column in the linkgit:git-ls-files[1] output above is the stage |
1c097891 BF |
3488 | number, and will take on values other than 0 for files with merge |
3489 | conflicts. | |
3490 | ||
3491 | The index is thus a sort of temporary staging area, which is filled with | |
3492 | a tree which you are in the process of working on. | |
3493 | ||
3494 | If you blow the index away entirely, you generally haven't lost any | |
3495 | information as long as you have the name of the tree that it described. | |
b181d57f | 3496 | |
38a457ba MV |
3497 | [[submodules]] |
3498 | Submodules | |
3499 | ========== | |
3500 | ||
6dd14366 MS |
3501 | Large projects are often composed of smaller, self-contained modules. For |
3502 | example, an embedded Linux distribution's source tree would include every | |
3503 | piece of software in the distribution with some local modifications; a movie | |
3504 | player might need to build against a specific, known-working version of a | |
3505 | decompression library; several independent programs might all share the same | |
3506 | build scripts. | |
3507 | ||
3508 | With centralized revision control systems this is often accomplished by | |
3509 | including every module in one single repository. Developers can check out | |
3510 | all modules or only the modules they need to work with. They can even modify | |
3511 | files across several modules in a single commit while moving things around | |
3512 | or updating APIs and translations. | |
3513 | ||
3514 | Git does not allow partial checkouts, so duplicating this approach in Git | |
3515 | would force developers to keep a local copy of modules they are not | |
3516 | interested in touching. Commits in an enormous checkout would be slower | |
3517 | than you'd expect as Git would have to scan every directory for changes. | |
3518 | If modules have a lot of local history, clones would take forever. | |
3519 | ||
3520 | On the plus side, distributed revision control systems can much better | |
3521 | integrate with external sources. In a centralized model, a single arbitrary | |
3522 | snapshot of the external project is exported from its own revision control | |
3523 | and then imported into the local revision control on a vendor branch. All | |
3524 | the history is hidden. With distributed revision control you can clone the | |
3525 | entire external history and much more easily follow development and re-merge | |
3526 | local changes. | |
3527 | ||
3528 | Git's submodule support allows a repository to contain, as a subdirectory, a | |
3529 | checkout of an external project. Submodules maintain their own identity; | |
3530 | the submodule support just stores the submodule repository location and | |
3531 | commit ID, so other developers who clone the containing project | |
3532 | ("superproject") can easily clone all the submodules at the same revision. | |
3533 | Partial checkouts of the superproject are possible: you can tell Git to | |
3534 | clone none, some or all of the submodules. | |
3535 | ||
5162e697 | 3536 | The linkgit:git-submodule[1] command is available since Git 1.5.3. Users |
6dd14366 MS |
3537 | with Git 1.5.2 can look up the submodule commits in the repository and |
3538 | manually check them out; earlier versions won't recognize the submodules at | |
3539 | all. | |
38a457ba MV |
3540 | |
3541 | To see how submodule support works, create (for example) four example | |
3542 | repositories that can be used later as a submodule: | |
3543 | ||
3544 | ------------------------------------------------- | |
3545 | $ mkdir ~/git | |
3546 | $ cd ~/git | |
3547 | $ for i in a b c d | |
3548 | do | |
3549 | mkdir $i | |
3550 | cd $i | |
3551 | git init | |
3552 | echo "module $i" > $i.txt | |
3553 | git add $i.txt | |
3554 | git commit -m "Initial commit, submodule $i" | |
3555 | cd .. | |
3556 | done | |
3557 | ------------------------------------------------- | |
3558 | ||
3559 | Now create the superproject and add all the submodules: | |
3560 | ||
3561 | ------------------------------------------------- | |
3562 | $ mkdir super | |
3563 | $ cd super | |
3564 | $ git init | |
3565 | $ for i in a b c d | |
3566 | do | |
a56bf585 | 3567 | git submodule add ~/git/$i $i |
38a457ba MV |
3568 | done |
3569 | ------------------------------------------------- | |
3570 | ||
3571 | NOTE: Do not use local URLs here if you plan to publish your superproject! | |
3572 | ||
6127c086 | 3573 | See what files `git submodule` created: |
38a457ba MV |
3574 | |
3575 | ------------------------------------------------- | |
3576 | $ ls -a | |
3577 | . .. .git .gitmodules a b c d | |
3578 | ------------------------------------------------- | |
3579 | ||
6127c086 | 3580 | The `git submodule add <repo> <path>` command does a couple of things: |
38a457ba | 3581 | |
1249d8ad | 3582 | - It clones the submodule from `<repo>` to the given `<path>` under the |
a56bf585 | 3583 | current directory and by default checks out the master branch. |
5162e697 | 3584 | - It adds the submodule's clone path to the linkgit:gitmodules[5] file and |
6dd14366 | 3585 | adds this file to the index, ready to be committed. |
38a457ba MV |
3586 | - It adds the submodule's current commit ID to the index, ready to be |
3587 | committed. | |
3588 | ||
3589 | Commit the superproject: | |
3590 | ||
3591 | ------------------------------------------------- | |
3592 | $ git commit -m "Add submodules a, b, c and d." | |
3593 | ------------------------------------------------- | |
3594 | ||
3595 | Now clone the superproject: | |
3596 | ||
3597 | ------------------------------------------------- | |
3598 | $ cd .. | |
3599 | $ git clone super cloned | |
3600 | $ cd cloned | |
3601 | ------------------------------------------------- | |
3602 | ||
3603 | The submodule directories are there, but they're empty: | |
3604 | ||
3605 | ------------------------------------------------- | |
3606 | $ ls -a a | |
3607 | . .. | |
3608 | $ git submodule status | |
3609 | -d266b9873ad50488163457f025db7cdd9683d88b a | |
3610 | -e81d457da15309b4fef4249aba9b50187999670d b | |
3611 | -c1536a972b9affea0f16e0680ba87332dc059146 c | |
3612 | -d96249ff5d57de5de093e6baff9e0aafa5276a74 d | |
3613 | ------------------------------------------------- | |
3614 | ||
3615 | NOTE: The commit object names shown above would be different for you, but they | |
3616 | should match the HEAD commit object names of your repositories. You can check | |
3617 | it by running `git ls-remote ../a`. | |
3618 | ||
3619 | Pulling down the submodules is a two-step process. First run `git submodule | |
3620 | init` to add the submodule repository URLs to `.git/config`: | |
3621 | ||
3622 | ------------------------------------------------- | |
3623 | $ git submodule init | |
3624 | ------------------------------------------------- | |
3625 | ||
6127c086 | 3626 | Now use `git submodule update` to clone the repositories and check out the |
38a457ba MV |
3627 | commits specified in the superproject: |
3628 | ||
3629 | ------------------------------------------------- | |
3630 | $ git submodule update | |
3631 | $ cd a | |
3632 | $ ls -a | |
3633 | . .. .git a.txt | |
3634 | ------------------------------------------------- | |
3635 | ||
6127c086 FC |
3636 | One major difference between `git submodule update` and `git submodule add` is |
3637 | that `git submodule update` checks out a specific commit, rather than the tip | |
38a457ba MV |
3638 | of a branch. It's like checking out a tag: the head is detached, so you're not |
3639 | working on a branch. | |
3640 | ||
3641 | ------------------------------------------------- | |
3642 | $ git branch | |
3643 | * (no branch) | |
3644 | master | |
3645 | ------------------------------------------------- | |
3646 | ||
3647 | If you want to make a change within a submodule and you have a detached head, | |
3648 | then you should create or checkout a branch, make your changes, publish the | |
3649 | change within the submodule, and then update the superproject to reference the | |
3650 | new commit: | |
3651 | ||
3652 | ------------------------------------------------- | |
3653 | $ git checkout master | |
3654 | ------------------------------------------------- | |
3655 | ||
3656 | or | |
3657 | ||
3658 | ------------------------------------------------- | |
3659 | $ git checkout -b fix-up | |
3660 | ------------------------------------------------- | |
3661 | ||
3662 | then | |
3663 | ||
3664 | ------------------------------------------------- | |
3665 | $ echo "adding a line again" >> a.txt | |
3666 | $ git commit -a -m "Updated the submodule from within the superproject." | |
3667 | $ git push | |
3668 | $ cd .. | |
3669 | $ git diff | |
3670 | diff --git a/a b/a | |
3671 | index d266b98..261dfac 160000 | |
3672 | --- a/a | |
3673 | +++ b/a | |
3674 | @@ -1 +1 @@ | |
3675 | -Subproject commit d266b9873ad50488163457f025db7cdd9683d88b | |
3676 | +Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24 | |
3677 | $ git add a | |
3678 | $ git commit -m "Updated submodule a." | |
3679 | $ git push | |
3680 | ------------------------------------------------- | |
3681 | ||
3682 | You have to run `git submodule update` after `git pull` if you want to update | |
3683 | submodules, too. | |
3684 | ||
3685 | Pitfalls with submodules | |
3686 | ------------------------ | |
3687 | ||
3688 | Always publish the submodule change before publishing the change to the | |
3689 | superproject that references it. If you forget to publish the submodule change, | |
3690 | others won't be able to clone the repository: | |
3691 | ||
3692 | ------------------------------------------------- | |
3693 | $ cd ~/git/super/a | |
3694 | $ echo i added another line to this file >> a.txt | |
3695 | $ git commit -a -m "doing it wrong this time" | |
3696 | $ cd .. | |
3697 | $ git add a | |
3698 | $ git commit -m "Updated submodule a again." | |
3699 | $ git push | |
3700 | $ cd ~/git/cloned | |
3701 | $ git pull | |
3702 | $ git submodule update | |
3703 | error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git. | |
3704 | Did you forget to 'git add'? | |
3705 | Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a' | |
3706 | ------------------------------------------------- | |
3707 | ||
2de9b711 | 3708 | In older Git versions it could be easily forgotten to commit new or modified |
8d9e7d52 | 3709 | files in a submodule, which silently leads to similar problems as not pushing |
1249d8ad | 3710 | the submodule changes. Starting with Git 1.7.0 both `git status` and `git diff` |
8d9e7d52 | 3711 | in the superproject show submodules as modified when they contain new or |
1249d8ad TK |
3712 | modified files to protect against accidentally committing such a state. `git |
3713 | diff` will also add a `-dirty` to the work tree side when generating patch | |
3714 | output or used with the `--submodule` option: | |
8d9e7d52 JL |
3715 | |
3716 | ------------------------------------------------- | |
3717 | $ git diff | |
3718 | diff --git a/sub b/sub | |
3719 | --- a/sub | |
3720 | +++ b/sub | |
3721 | @@ -1 +1 @@ | |
3722 | -Subproject commit 3f356705649b5d566d97ff843cf193359229a453 | |
3723 | +Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty | |
3724 | $ git diff --submodule | |
3725 | Submodule sub 3f35670..3f35670-dirty: | |
3726 | ------------------------------------------------- | |
3727 | ||
38a457ba MV |
3728 | You also should not rewind branches in a submodule beyond commits that were |
3729 | ever recorded in any superproject. | |
3730 | ||
3731 | It's not safe to run `git submodule update` if you've made and committed | |
3732 | changes within a submodule without checking out a branch first. They will be | |
3733 | silently overwritten: | |
3734 | ||
3735 | ------------------------------------------------- | |
3736 | $ cat a.txt | |
3737 | module a | |
3738 | $ echo line added from private2 >> a.txt | |
3739 | $ git commit -a -m "line added inside private2" | |
3740 | $ cd .. | |
3741 | $ git submodule update | |
3742 | Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b' | |
3743 | $ cd a | |
3744 | $ cat a.txt | |
3745 | module a | |
3746 | ------------------------------------------------- | |
3747 | ||
3748 | NOTE: The changes are still visible in the submodule's reflog. | |
3749 | ||
91486733 TK |
3750 | If you have uncommitted changes in your submodule working tree, `git |
3751 | submodule update` will not overwrite them. Instead, you get the usual | |
3752 | warning about not being able switch from a dirty branch. | |
38a457ba | 3753 | |
1c6045ff | 3754 | [[low-level-operations]] |
2de9b711 | 3755 | Low-level Git operations |
1c6045ff | 3756 | ======================== |
b181d57f | 3757 | |
1c6045ff | 3758 | Many of the higher-level commands were originally implemented as shell |
2de9b711 TA |
3759 | scripts using a smaller core of low-level Git commands. These can still |
3760 | be useful when doing unusual things with Git, or just as a way to | |
1c6045ff | 3761 | understand its inner workings. |
b181d57f | 3762 | |
1bbf1c79 BF |
3763 | [[object-manipulation]] |
3764 | Object access and manipulation | |
3765 | ------------------------------ | |
3766 | ||
5162e697 DM |
3767 | The linkgit:git-cat-file[1] command can show the contents of any object, |
3768 | though the higher-level linkgit:git-show[1] is usually more useful. | |
1bbf1c79 | 3769 | |
5162e697 | 3770 | The linkgit:git-commit-tree[1] command allows constructing commits with |
1bbf1c79 BF |
3771 | arbitrary parents and trees. |
3772 | ||
5162e697 DM |
3773 | A tree can be created with linkgit:git-write-tree[1] and its data can be |
3774 | accessed by linkgit:git-ls-tree[1]. Two trees can be compared with | |
3775 | linkgit:git-diff-tree[1]. | |
1bbf1c79 | 3776 | |
5162e697 DM |
3777 | A tag is created with linkgit:git-mktag[1], and the signature can be |
3778 | verified by linkgit:git-verify-tag[1], though it is normally simpler to | |
3779 | use linkgit:git-tag[1] for both. | |
1bbf1c79 | 3780 | |
e34caace | 3781 | [[the-workflow]] |
b181d57f BF |
3782 | The Workflow |
3783 | ------------ | |
3784 | ||
5162e697 DM |
3785 | High-level operations such as linkgit:git-commit[1], |
3786 | linkgit:git-checkout[1] and linkgit:git-reset[1] work by moving data | |
06ada152 RW |
3787 | between the working tree, the index, and the object database. Git |
3788 | provides low-level operations which perform each of these steps | |
3789 | individually. | |
1c6045ff | 3790 | |
2de9b711 | 3791 | Generally, all Git operations work on the index file. Some operations |
b181d57f | 3792 | work *purely* on the index file (showing the current state of the |
1c6045ff BF |
3793 | index), but most operations move data between the index file and either |
3794 | the database or the working directory. Thus there are four main | |
3795 | combinations: | |
b181d57f | 3796 | |
e34caace | 3797 | [[working-directory-to-index]] |
b181d57f BF |
3798 | working directory -> index |
3799 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3800 | ||
5162e697 | 3801 | The linkgit:git-update-index[1] command updates the index with |
1c6045ff BF |
3802 | information from the working directory. You generally update the |
3803 | index information by just specifying the filename you want to update, | |
3804 | like so: | |
b181d57f BF |
3805 | |
3806 | ------------------------------------------------- | |
1c6045ff | 3807 | $ git update-index filename |
b181d57f BF |
3808 | ------------------------------------------------- |
3809 | ||
3810 | but to avoid common mistakes with filename globbing etc, the command | |
3811 | will not normally add totally new entries or remove old entries, | |
3812 | i.e. it will normally just update existing cache entries. | |
3813 | ||
2de9b711 | 3814 | To tell Git that yes, you really do realize that certain files no |
b181d57f BF |
3815 | longer exist, or that new files should be added, you |
3816 | should use the `--remove` and `--add` flags respectively. | |
3817 | ||
3818 | NOTE! A `--remove` flag does 'not' mean that subsequent filenames will | |
3819 | necessarily be removed: if the files still exist in your directory | |
3820 | structure, the index will be updated with their new status, not | |
10455d2a | 3821 | removed. The only thing `--remove` means is that update-index will be |
b181d57f BF |
3822 | considering a removed file to be a valid thing, and if the file really |
3823 | does not exist any more, it will update the index accordingly. | |
3824 | ||
467c0197 | 3825 | As a special case, you can also do `git update-index --refresh`, which |
b181d57f BF |
3826 | will refresh the "stat" information of each index to match the current |
3827 | stat information. It will 'not' update the object status itself, and | |
3828 | it will only update the fields that are used to quickly test whether | |
3829 | an object still matches its old backing store object. | |
3830 | ||
5162e697 DM |
3831 | The previously introduced linkgit:git-add[1] is just a wrapper for |
3832 | linkgit:git-update-index[1]. | |
1c6045ff | 3833 | |
e34caace | 3834 | [[index-to-object-database]] |
b181d57f BF |
3835 | index -> object database |
3836 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
3837 | ||
3838 | You write your current index file to a "tree" object with the program | |
3839 | ||
3840 | ------------------------------------------------- | |
1c6045ff | 3841 | $ git write-tree |
b181d57f BF |
3842 | ------------------------------------------------- |
3843 | ||
2ef8ac1b | 3844 | that doesn't come with any options--it will just write out the |
b181d57f BF |
3845 | current index into the set of tree objects that describe that state, |
3846 | and it will return the name of the resulting top-level tree. You can | |
3847 | use that tree to re-generate the index at any time by going in the | |
3848 | other direction: | |
3849 | ||
e34caace | 3850 | [[object-database-to-index]] |
b181d57f BF |
3851 | object database -> index |
3852 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
3853 | ||
3854 | You read a "tree" file from the object database, and use that to | |
2ef8ac1b | 3855 | populate (and overwrite--don't do this if your index contains any |
b181d57f BF |
3856 | unsaved state that you might want to restore later!) your current |
3857 | index. Normal operation is just | |
3858 | ||
3859 | ------------------------------------------------- | |
a6e5ef7d | 3860 | $ git read-tree <SHA-1 of tree> |
b181d57f BF |
3861 | ------------------------------------------------- |
3862 | ||
3863 | and your index file will now be equivalent to the tree that you saved | |
3864 | earlier. However, that is only your 'index' file: your working | |
3865 | directory contents have not been modified. | |
3866 | ||
e34caace | 3867 | [[index-to-working-directory]] |
b181d57f BF |
3868 | index -> working directory |
3869 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
3870 | ||
3871 | You update your working directory from the index by "checking out" | |
3872 | files. This is not a very common operation, since normally you'd just | |
3873 | keep your files updated, and rather than write to your working | |
3874 | directory, you'd tell the index files about the changes in your | |
6127c086 | 3875 | working directory (i.e. `git update-index`). |
b181d57f BF |
3876 | |
3877 | However, if you decide to jump to a new version, or check out somebody | |
3878 | else's version, or just restore a previous tree, you'd populate your | |
3879 | index file with read-tree, and then you need to check out the result | |
3880 | with | |
3881 | ||
3882 | ------------------------------------------------- | |
b1889c36 | 3883 | $ git checkout-index filename |
b181d57f BF |
3884 | ------------------------------------------------- |
3885 | ||
3886 | or, if you want to check out all of the index, use `-a`. | |
3887 | ||
6127c086 | 3888 | NOTE! `git checkout-index` normally refuses to overwrite old files, so |
b181d57f | 3889 | if you have an old version of the tree already checked out, you will |
1249d8ad | 3890 | need to use the `-f` flag ('before' the `-a` flag or the filename) to |
b181d57f BF |
3891 | 'force' the checkout. |
3892 | ||
3893 | ||
3894 | Finally, there are a few odds and ends which are not purely moving | |
3895 | from one representation to the other: | |
3896 | ||
e34caace | 3897 | [[tying-it-all-together]] |
b181d57f BF |
3898 | Tying it all together |
3899 | ~~~~~~~~~~~~~~~~~~~~~ | |
3900 | ||
1249d8ad | 3901 | To commit a tree you have instantiated with `git write-tree`, you'd |
b181d57f | 3902 | create a "commit" object that refers to that tree and the history |
2ef8ac1b | 3903 | behind it--most notably the "parent" commits that preceded it in |
b181d57f BF |
3904 | history. |
3905 | ||
3906 | Normally a "commit" has one parent: the previous state of the tree | |
3907 | before a certain change was made. However, sometimes it can have two | |
3908 | or more parent commits, in which case we call it a "merge", due to the | |
3909 | fact that such a commit brings together ("merges") two or more | |
3910 | previous states represented by other commits. | |
3911 | ||
3912 | In other words, while a "tree" represents a particular directory state | |
3913 | of a working directory, a "commit" represents that state in "time", | |
3914 | and explains how we got there. | |
3915 | ||
3916 | You create a commit object by giving it the tree that describes the | |
3917 | state at the time of the commit, and a list of parents: | |
3918 | ||
3919 | ------------------------------------------------- | |
0adda936 | 3920 | $ git commit-tree <tree> -p <parent> [(-p <parent2>)...] |
b181d57f BF |
3921 | ------------------------------------------------- |
3922 | ||
3923 | and then giving the reason for the commit on stdin (either through | |
3924 | redirection from a pipe or file, or by just typing it at the tty). | |
3925 | ||
6127c086 | 3926 | `git commit-tree` will return the name of the object that represents |
b181d57f | 3927 | that commit, and you should save it away for later use. Normally, |
2de9b711 | 3928 | you'd commit a new `HEAD` state, and while Git doesn't care where you |
b181d57f BF |
3929 | save the note about that state, in practice we tend to just write the |
3930 | result to the file pointed at by `.git/HEAD`, so that we can always see | |
3931 | what the last committed state was. | |
3932 | ||
3933 | Here is an ASCII art by Jon Loeliger that illustrates how | |
3934 | various pieces fit together. | |
3935 | ||
3936 | ------------ | |
3937 | ||
3938 | commit-tree | |
3939 | commit obj | |
3940 | +----+ | |
3941 | | | | |
3942 | | | | |
3943 | V V | |
3944 | +-----------+ | |
3945 | | Object DB | | |
3946 | | Backing | | |
3947 | | Store | | |
3948 | +-----------+ | |
3949 | ^ | |
3950 | write-tree | | | |
3951 | tree obj | | | |
3952 | | | read-tree | |
3953 | | | tree obj | |
3954 | V | |
3955 | +-----------+ | |
3956 | | Index | | |
3957 | | "cache" | | |
3958 | +-----------+ | |
3959 | update-index ^ | |
3960 | blob obj | | | |
3961 | | | | |
3962 | checkout-index -u | | checkout-index | |
3963 | stat | | blob obj | |
3964 | V | |
3965 | +-----------+ | |
3966 | | Working | | |
3967 | | Directory | | |
3968 | +-----------+ | |
3969 | ||
3970 | ------------ | |
3971 | ||
3972 | ||
e34caace | 3973 | [[examining-the-data]] |
b181d57f BF |
3974 | Examining the data |
3975 | ------------------ | |
3976 | ||
3977 | You can examine the data represented in the object database and the | |
3978 | index with various helper tools. For every object, you can use | |
5162e697 | 3979 | linkgit:git-cat-file[1] to examine details about the |
b181d57f BF |
3980 | object: |
3981 | ||
3982 | ------------------------------------------------- | |
b1889c36 | 3983 | $ git cat-file -t <objectname> |
b181d57f BF |
3984 | ------------------------------------------------- |
3985 | ||
3986 | shows the type of the object, and once you have the type (which is | |
3987 | usually implicit in where you find the object), you can use | |
3988 | ||
3989 | ------------------------------------------------- | |
b1889c36 | 3990 | $ git cat-file blob|tree|commit|tag <objectname> |
b181d57f BF |
3991 | ------------------------------------------------- |
3992 | ||
3993 | to show its contents. NOTE! Trees have binary content, and as a result | |
3994 | there is a special helper for showing that content, called | |
6127c086 | 3995 | `git ls-tree`, which turns the binary content into a more easily |
b181d57f BF |
3996 | readable form. |
3997 | ||
3998 | It's especially instructive to look at "commit" objects, since those | |
3999 | tend to be small and fairly self-explanatory. In particular, if you | |
4000 | follow the convention of having the top commit name in `.git/HEAD`, | |
4001 | you can do | |
4002 | ||
4003 | ------------------------------------------------- | |
b1889c36 | 4004 | $ git cat-file commit HEAD |
b181d57f BF |
4005 | ------------------------------------------------- |
4006 | ||
4007 | to see what the top commit was. | |
4008 | ||
e34caace | 4009 | [[merging-multiple-trees]] |
b181d57f | 4010 | Merging multiple trees |
d19fbc3c BF |
4011 | ---------------------- |
4012 | ||
b181d57f BF |
4013 | Git helps you do a three-way merge, which you can expand to n-way by |
4014 | repeating the merge procedure arbitrary times until you finally | |
4015 | "commit" the state. The normal situation is that you'd only do one | |
4016 | three-way merge (two parents), and commit it, but if you like to, you | |
4017 | can do multiple parents in one go. | |
4018 | ||
4019 | To do a three-way merge, you need the two sets of "commit" objects | |
4020 | that you want to merge, use those to find the closest common parent (a | |
4021 | third "commit" object), and then use those commit objects to find the | |
4022 | state of the directory ("tree" object) at these points. | |
4023 | ||
4024 | To get the "base" for the merge, you first look up the common parent | |
4025 | of two commits with | |
4026 | ||
4027 | ------------------------------------------------- | |
b1889c36 | 4028 | $ git merge-base <commit1> <commit2> |
b181d57f BF |
4029 | ------------------------------------------------- |
4030 | ||
4031 | which will return you the commit they are both based on. You should | |
4032 | now look up the "tree" objects of those commits, which you can easily | |
4033 | do with (for example) | |
4034 | ||
4035 | ------------------------------------------------- | |
b1889c36 | 4036 | $ git cat-file commit <commitname> | head -1 |
b181d57f BF |
4037 | ------------------------------------------------- |
4038 | ||
4039 | since the tree object information is always the first line in a commit | |
4040 | object. | |
4041 | ||
1191ee18 | 4042 | Once you know the three trees you are going to merge (the one "original" |
c64415e2 | 4043 | tree, aka the common tree, and the two "result" trees, aka the branches |
1191ee18 BF |
4044 | you want to merge), you do a "merge" read into the index. This will |
4045 | complain if it has to throw away your old index contents, so you should | |
2ef8ac1b | 4046 | make sure that you've committed those--in fact you would normally |
1191ee18 BF |
4047 | always do a merge against your last commit (which should thus match what |
4048 | you have in your current index anyway). | |
b181d57f BF |
4049 | |
4050 | To do the merge, do | |
4051 | ||
4052 | ------------------------------------------------- | |
b1889c36 | 4053 | $ git read-tree -m -u <origtree> <yourtree> <targettree> |
b181d57f BF |
4054 | ------------------------------------------------- |
4055 | ||
4056 | which will do all trivial merge operations for you directly in the | |
4057 | index file, and you can just write the result out with | |
467c0197 | 4058 | `git write-tree`. |
b181d57f BF |
4059 | |
4060 | ||
e34caace | 4061 | [[merging-multiple-trees-2]] |
b181d57f BF |
4062 | Merging multiple trees, continued |
4063 | --------------------------------- | |
4064 | ||
4065 | Sadly, many merges aren't trivial. If there are files that have | |
06ada152 | 4066 | been added, moved or removed, or if both branches have modified the |
b181d57f BF |
4067 | same file, you will be left with an index tree that contains "merge |
4068 | entries" in it. Such an index tree can 'NOT' be written out to a tree | |
4069 | object, and you will have to resolve any such merge clashes using | |
4070 | other tools before you can write out the result. | |
4071 | ||
b1889c36 | 4072 | You can examine such index state with `git ls-files --unmerged` |
b181d57f BF |
4073 | command. An example: |
4074 | ||
4075 | ------------------------------------------------ | |
b1889c36 JN |
4076 | $ git read-tree -m $orig HEAD $target |
4077 | $ git ls-files --unmerged | |
b181d57f BF |
4078 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c |
4079 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c | |
4080 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c | |
4081 | ------------------------------------------------ | |
4082 | ||
b1889c36 | 4083 | Each line of the `git ls-files --unmerged` output begins with |
a6e5ef7d | 4084 | the blob mode bits, blob SHA-1, 'stage number', and the |
2de9b711 | 4085 | filename. The 'stage number' is Git's way to say which tree it |
edfbbf7e ŠN |
4086 | came from: stage 1 corresponds to the `$orig` tree, stage 2 to |
4087 | the `HEAD` tree, and stage 3 to the `$target` tree. | |
b181d57f BF |
4088 | |
4089 | Earlier we said that trivial merges are done inside | |
6127c086 | 4090 | `git read-tree -m`. For example, if the file did not change |
b181d57f BF |
4091 | from `$orig` to `HEAD` nor `$target`, or if the file changed |
4092 | from `$orig` to `HEAD` and `$orig` to `$target` the same way, | |
4093 | obviously the final outcome is what is in `HEAD`. What the | |
4094 | above example shows is that file `hello.c` was changed from | |
4095 | `$orig` to `HEAD` and `$orig` to `$target` in a different way. | |
4096 | You could resolve this by running your favorite 3-way merge | |
2de9b711 | 4097 | program, e.g. `diff3`, `merge`, or Git's own merge-file, on |
c64415e2 | 4098 | the blob objects from these three stages yourself, like this: |
b181d57f BF |
4099 | |
4100 | ------------------------------------------------ | |
b1889c36 JN |
4101 | $ git cat-file blob 263414f... >hello.c~1 |
4102 | $ git cat-file blob 06fa6a2... >hello.c~2 | |
4103 | $ git cat-file blob cc44c73... >hello.c~3 | |
c64415e2 | 4104 | $ git merge-file hello.c~2 hello.c~1 hello.c~3 |
b181d57f BF |
4105 | ------------------------------------------------ |
4106 | ||
4107 | This would leave the merge result in `hello.c~2` file, along | |
4108 | with conflict markers if there are conflicts. After verifying | |
2de9b711 | 4109 | the merge result makes sense, you can tell Git what the final |
b181d57f BF |
4110 | merge result for this file is by: |
4111 | ||
4112 | ------------------------------------------------- | |
4113 | $ mv -f hello.c~2 hello.c | |
b1889c36 | 4114 | $ git update-index hello.c |
b181d57f BF |
4115 | ------------------------------------------------- |
4116 | ||
6127c086 | 4117 | When a path is in the "unmerged" state, running `git update-index` for |
2de9b711 | 4118 | that path tells Git to mark the path resolved. |
b181d57f | 4119 | |
2de9b711 | 4120 | The above is the description of a Git merge at the lowest level, |
b181d57f | 4121 | to help you understand what conceptually happens under the hood. |
2de9b711 | 4122 | In practice, nobody, not even Git itself, runs `git cat-file` three times |
6127c086 | 4123 | for this. There is a `git merge-index` program that extracts the |
b181d57f BF |
4124 | stages to temporary files and calls a "merge" script on it: |
4125 | ||
4126 | ------------------------------------------------- | |
b1889c36 | 4127 | $ git merge-index git-merge-one-file hello.c |
b181d57f BF |
4128 | ------------------------------------------------- |
4129 | ||
6127c086 | 4130 | and that is what higher level `git merge -s resolve` is implemented with. |
b181d57f | 4131 | |
971aa71f | 4132 | [[hacking-git]] |
2de9b711 | 4133 | Hacking Git |
971aa71f BF |
4134 | =========== |
4135 | ||
2de9b711 TA |
4136 | This chapter covers internal details of the Git implementation which |
4137 | probably only Git developers need to understand. | |
971aa71f | 4138 | |
f2327c6c BF |
4139 | [[object-details]] |
4140 | Object storage format | |
4141 | --------------------- | |
4142 | ||
4143 | All objects have a statically determined "type" which identifies the | |
4144 | format of the object (i.e. how it is used, and how it can refer to other | |
4145 | objects). There are currently four different object types: "blob", | |
4146 | "tree", "commit", and "tag". | |
4147 | ||
4148 | Regardless of object type, all objects share the following | |
4149 | characteristics: they are all deflated with zlib, and have a header | |
4150 | that not only specifies their type, but also provides size information | |
a6e5ef7d | 4151 | about the data in the object. It's worth noting that the SHA-1 hash |
f2327c6c BF |
4152 | that is used to name the object is the hash of the original data |
4153 | plus this header, so `sha1sum` 'file' does not match the object name | |
4154 | for 'file'. | |
2de9b711 | 4155 | (Historical note: in the dawn of the age of Git the hash |
a6e5ef7d | 4156 | was the SHA-1 of the 'compressed' object.) |
f2327c6c BF |
4157 | |
4158 | As a result, the general consistency of an object can always be tested | |
4159 | independently of the contents or the type of the object: all objects can | |
4160 | be validated by verifying that (a) their hashes match the content of the | |
4161 | file and (b) the object successfully inflates to a stream of bytes that | |
1249d8ad TK |
4162 | forms a sequence of |
4163 | `<ascii type without space> + <space> + <ascii decimal size> + | |
4164 | <byte\0> + <binary object data>`. | |
f2327c6c BF |
4165 | |
4166 | The structured objects can further have their structure and | |
4167 | connectivity to other objects verified. This is generally done with | |
6127c086 | 4168 | the `git fsck` program, which generates a full dependency graph |
f2327c6c BF |
4169 | of all objects, and verifies their internal consistency (in addition |
4170 | to just verifying their superficial consistency through the hash). | |
4171 | ||
126640af | 4172 | [[birdview-on-the-source-code]] |
a5fc33b4 BF |
4173 | A birds-eye view of Git's source code |
4174 | ------------------------------------- | |
126640af | 4175 | |
a5fc33b4 BF |
4176 | It is not always easy for new developers to find their way through Git's |
4177 | source code. This section gives you a little guidance to show where to | |
4178 | start. | |
126640af | 4179 | |
a5fc33b4 | 4180 | A good place to start is with the contents of the initial commit, with: |
126640af JS |
4181 | |
4182 | ---------------------------------------------------- | |
a5fc33b4 | 4183 | $ git checkout e83c5163 |
126640af JS |
4184 | ---------------------------------------------------- |
4185 | ||
2de9b711 | 4186 | The initial revision lays the foundation for almost everything Git has |
a5fc33b4 | 4187 | today, but is small enough to read in one sitting. |
126640af | 4188 | |
a5fc33b4 BF |
4189 | Note that terminology has changed since that revision. For example, the |
4190 | README in that revision uses the word "changeset" to describe what we | |
4191 | now call a <<def_commit_object,commit>>. | |
126640af | 4192 | |
843c81dc | 4193 | Also, we do not call it "cache" any more, but rather "index"; however, the |
126640af JS |
4194 | file is still called `cache.h`. Remark: Not much reason to change it now, |
4195 | especially since there is no good single name for it anyway, because it is | |
4196 | basically _the_ header file which is included by _all_ of Git's C sources. | |
4197 | ||
a5fc33b4 BF |
4198 | If you grasp the ideas in that initial commit, you should check out a |
4199 | more recent version and skim `cache.h`, `object.h` and `commit.h`. | |
126640af JS |
4200 | |
4201 | In the early days, Git (in the tradition of UNIX) was a bunch of programs | |
4202 | which were extremely simple, and which you used in scripts, piping the | |
4203 | output of one into another. This turned out to be good for initial | |
4204 | development, since it was easier to test new things. However, recently | |
4205 | many of these parts have become builtins, and some of the core has been | |
4206 | "libified", i.e. put into libgit.a for performance, portability reasons, | |
4207 | and to avoid code duplication. | |
4208 | ||
4209 | By now, you know what the index is (and find the corresponding data | |
4210 | structures in `cache.h`), and that there are just a couple of object types | |
4211 | (blobs, trees, commits and tags) which inherit their common structure from | |
4212 | `struct object`, which is their first member (and thus, you can cast e.g. | |
4213 | `(struct object *)commit` to achieve the _same_ as `&commit->object`, i.e. | |
4214 | get at the object name and flags). | |
4215 | ||
4216 | Now is a good point to take a break to let this information sink in. | |
4217 | ||
4218 | Next step: get familiar with the object naming. Read <<naming-commits>>. | |
4219 | There are quite a few ways to name an object (and not only revisions!). | |
4220 | All of these are handled in `sha1_name.c`. Just have a quick look at | |
4221 | the function `get_sha1()`. A lot of the special handling is done by | |
4222 | functions like `get_sha1_basic()` or the likes. | |
4223 | ||
4224 | This is just to get you into the groove for the most libified part of Git: | |
4225 | the revision walker. | |
4226 | ||
6127c086 | 4227 | Basically, the initial version of `git log` was a shell script: |
126640af JS |
4228 | |
4229 | ---------------------------------------------------------------- | |
4230 | $ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ | |
4231 | LESS=-S ${PAGER:-less} | |
4232 | ---------------------------------------------------------------- | |
4233 | ||
4234 | What does this mean? | |
4235 | ||
6127c086 | 4236 | `git rev-list` is the original version of the revision walker, which |
126640af | 4237 | _always_ printed a list of revisions to stdout. It is still functional, |
57f6ec02 | 4238 | and needs to, since most new Git commands start out as scripts using |
6127c086 | 4239 | `git rev-list`. |
126640af | 4240 | |
6127c086 | 4241 | `git rev-parse` is not as important any more; it was only used to filter out |
126640af JS |
4242 | options that were relevant for the different plumbing commands that were |
4243 | called by the script. | |
4244 | ||
6127c086 | 4245 | Most of what `git rev-list` did is contained in `revision.c` and |
126640af JS |
4246 | `revision.h`. It wraps the options in a struct named `rev_info`, which |
4247 | controls how and what revisions are walked, and more. | |
4248 | ||
6127c086 | 4249 | The original job of `git rev-parse` is now taken by the function |
126640af JS |
4250 | `setup_revisions()`, which parses the revisions and the common command line |
4251 | options for the revision walker. This information is stored in the struct | |
4252 | `rev_info` for later consumption. You can do your own command line option | |
4253 | parsing after calling `setup_revisions()`. After that, you have to call | |
4254 | `prepare_revision_walk()` for initialization, and then you can get the | |
4255 | commits one by one with the function `get_revision()`. | |
4256 | ||
4257 | If you are interested in more details of the revision walking process, | |
4258 | just have a look at the first implementation of `cmd_log()`; call | |
6cf378f0 | 4259 | `git show v1.3.0~155^2~4` and scroll down to that function (note that you |
126640af JS |
4260 | no longer need to call `setup_pager()` directly). |
4261 | ||
6127c086 | 4262 | Nowadays, `git log` is a builtin, which means that it is _contained_ in the |
126640af JS |
4263 | command `git`. The source side of a builtin is |
4264 | ||
09b7e220 PH |
4265 | - a function called `cmd_<bla>`, typically defined in `builtin/<bla.c>` |
4266 | (note that older versions of Git used to have it in `builtin-<bla>.c` | |
4267 | instead), and declared in `builtin.h`. | |
126640af JS |
4268 | |
4269 | - an entry in the `commands[]` array in `git.c`, and | |
4270 | ||
4271 | - an entry in `BUILTIN_OBJECTS` in the `Makefile`. | |
4272 | ||
4273 | Sometimes, more than one builtin is contained in one source file. For | |
09b7e220 | 4274 | example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin/log.c`, |
126640af JS |
4275 | since they share quite a bit of code. In that case, the commands which are |
4276 | _not_ named like the `.c` file in which they live have to be listed in | |
4277 | `BUILT_INS` in the `Makefile`. | |
4278 | ||
6127c086 | 4279 | `git log` looks more complicated in C than it does in the original script, |
126640af JS |
4280 | but that allows for a much greater flexibility and performance. |
4281 | ||
4282 | Here again it is a good point to take a pause. | |
4283 | ||
4284 | Lesson three is: study the code. Really, it is the best way to learn about | |
4285 | the organization of Git (after you know the basic concepts). | |
4286 | ||
4287 | So, think about something which you are interested in, say, "how can I | |
4288 | access a blob just knowing the object name of it?". The first step is to | |
4289 | find a Git command with which you can do it. In this example, it is either | |
6127c086 | 4290 | `git show` or `git cat-file`. |
126640af | 4291 | |
6127c086 | 4292 | For the sake of clarity, let's stay with `git cat-file`, because it |
126640af JS |
4293 | |
4294 | - is plumbing, and | |
4295 | ||
4296 | - was around even in the initial commit (it literally went only through | |
09b7e220 | 4297 | some 20 revisions as `cat-file.c`, was renamed to `builtin/cat-file.c` |
126640af JS |
4298 | when made a builtin, and then saw less than 10 versions). |
4299 | ||
09b7e220 | 4300 | So, look into `builtin/cat-file.c`, search for `cmd_cat_file()` and look what |
126640af JS |
4301 | it does. |
4302 | ||
4303 | ------------------------------------------------------------------ | |
4304 | git_config(git_default_config); | |
4305 | if (argc != 3) | |
6127c086 | 4306 | usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>"); |
126640af JS |
4307 | if (get_sha1(argv[2], sha1)) |
4308 | die("Not a valid object name %s", argv[2]); | |
4309 | ------------------------------------------------------------------ | |
4310 | ||
4311 | Let's skip over the obvious details; the only really interesting part | |
4312 | here is the call to `get_sha1()`. It tries to interpret `argv[2]` as an | |
4313 | object name, and if it refers to an object which is present in the current | |
4314 | repository, it writes the resulting SHA-1 into the variable `sha1`. | |
4315 | ||
4316 | Two things are interesting here: | |
4317 | ||
4318 | - `get_sha1()` returns 0 on _success_. This might surprise some new | |
4319 | Git hackers, but there is a long tradition in UNIX to return different | |
2ef8ac1b | 4320 | negative numbers in case of different errors--and 0 on success. |
126640af JS |
4321 | |
4322 | - the variable `sha1` in the function signature of `get_sha1()` is `unsigned | |
6cf378f0 | 4323 | char *`, but is actually expected to be a pointer to `unsigned |
126640af | 4324 | char[20]`. This variable will contain the 160-bit SHA-1 of the given |
6cf378f0 | 4325 | commit. Note that whenever a SHA-1 is passed as `unsigned char *`, it |
126640af | 4326 | is the binary representation, as opposed to the ASCII representation in |
a5fc33b4 | 4327 | hex characters, which is passed as `char *`. |
126640af JS |
4328 | |
4329 | You will see both of these things throughout the code. | |
4330 | ||
4331 | Now, for the meat: | |
4332 | ||
4333 | ----------------------------------------------------------------------------- | |
4334 | case 0: | |
4335 | buf = read_object_with_reference(sha1, argv[1], &size, NULL); | |
4336 | ----------------------------------------------------------------------------- | |
4337 | ||
4338 | This is how you read a blob (actually, not only a blob, but any type of | |
4339 | object). To know how the function `read_object_with_reference()` actually | |
4340 | works, find the source code for it (something like `git grep | |
2de9b711 | 4341 | read_object_with | grep ":[a-z]"` in the Git repository), and read |
126640af JS |
4342 | the source. |
4343 | ||
4344 | To find out how the result can be used, just read on in `cmd_cat_file()`: | |
4345 | ||
4346 | ----------------------------------- | |
4347 | write_or_die(1, buf, size); | |
4348 | ----------------------------------- | |
4349 | ||
4350 | Sometimes, you do not know where to look for a feature. In many such cases, | |
6127c086 | 4351 | it helps to search through the output of `git log`, and then `git show` the |
126640af JS |
4352 | corresponding commit. |
4353 | ||
6127c086 | 4354 | Example: If you know that there was some test case for `git bundle`, but |
126640af JS |
4355 | do not remember where it was (yes, you _could_ `git grep bundle t/`, but that |
4356 | does not illustrate the point!): | |
4357 | ||
4358 | ------------------------ | |
4359 | $ git log --no-merges t/ | |
4360 | ------------------------ | |
4361 | ||
4362 | In the pager (`less`), just search for "bundle", go a few lines back, | |
4363 | and see that it is in commit 18449ab0... Now just copy this object name, | |
4364 | and paste it into the command line | |
4365 | ||
4366 | ------------------- | |
4367 | $ git show 18449ab0 | |
4368 | ------------------- | |
4369 | ||
4370 | Voila. | |
4371 | ||
4372 | Another example: Find out what to do in order to make some script a | |
4373 | builtin: | |
4374 | ||
4375 | ------------------------------------------------- | |
09b7e220 | 4376 | $ git log --no-merges --diff-filter=A builtin/*.c |
126640af JS |
4377 | ------------------------------------------------- |
4378 | ||
4379 | You see, Git is actually the best tool to find out about the source of Git | |
4380 | itself! | |
4381 | ||
e34caace | 4382 | [[glossary]] |
73a1d050 | 4383 | Git Glossary |
497c8331 CC |
4384 | ============ |
4385 | ||
4386 | include::glossary-content.txt[] | |
d19fbc3c | 4387 | |
2624d9a5 | 4388 | [[git-quick-start]] |
99f171bb BF |
4389 | Appendix A: Git Quick Reference |
4390 | =============================== | |
2624d9a5 | 4391 | |
99f171bb BF |
4392 | This is a quick summary of the major commands; the previous chapters |
4393 | explain how these work in more detail. | |
2624d9a5 BF |
4394 | |
4395 | [[quick-creating-a-new-repository]] | |
4396 | Creating a new repository | |
4397 | ------------------------- | |
4398 | ||
4399 | From a tarball: | |
4400 | ||
4401 | ----------------------------------------------- | |
4402 | $ tar xzf project.tar.gz | |
4403 | $ cd project | |
4404 | $ git init | |
4405 | Initialized empty Git repository in .git/ | |
4406 | $ git add . | |
4407 | $ git commit | |
4408 | ----------------------------------------------- | |
4409 | ||
4410 | From a remote repository: | |
4411 | ||
4412 | ----------------------------------------------- | |
4413 | $ git clone git://example.com/pub/project.git | |
4414 | $ cd project | |
4415 | ----------------------------------------------- | |
4416 | ||
4417 | [[managing-branches]] | |
4418 | Managing branches | |
4419 | ----------------- | |
4420 | ||
4421 | ----------------------------------------------- | |
4422 | $ git branch # list all local branches in this repo | |
4423 | $ git checkout test # switch working directory to branch "test" | |
4424 | $ git branch new # create branch "new" starting at current HEAD | |
4425 | $ git branch -d new # delete branch "new" | |
4426 | ----------------------------------------------- | |
4427 | ||
06ada152 | 4428 | Instead of basing a new branch on current HEAD (the default), use: |
2624d9a5 BF |
4429 | |
4430 | ----------------------------------------------- | |
4431 | $ git branch new test # branch named "test" | |
4432 | $ git branch new v2.6.15 # tag named v2.6.15 | |
4433 | $ git branch new HEAD^ # commit before the most recent | |
4434 | $ git branch new HEAD^^ # commit before that | |
4435 | $ git branch new test~10 # ten commits before tip of branch "test" | |
4436 | ----------------------------------------------- | |
4437 | ||
4438 | Create and switch to a new branch at the same time: | |
4439 | ||
4440 | ----------------------------------------------- | |
4441 | $ git checkout -b new v2.6.15 | |
4442 | ----------------------------------------------- | |
4443 | ||
4444 | Update and examine branches from the repository you cloned from: | |
4445 | ||
4446 | ----------------------------------------------- | |
4447 | $ git fetch # update | |
4448 | $ git branch -r # list | |
4449 | origin/master | |
4450 | origin/next | |
4451 | ... | |
4452 | $ git checkout -b masterwork origin/master | |
4453 | ----------------------------------------------- | |
4454 | ||
4455 | Fetch a branch from a different repository, and give it a new | |
4456 | name in your repository: | |
4457 | ||
4458 | ----------------------------------------------- | |
4459 | $ git fetch git://example.com/project.git theirbranch:mybranch | |
4460 | $ git fetch git://example.com/project.git v2.6.15:mybranch | |
4461 | ----------------------------------------------- | |
4462 | ||
4463 | Keep a list of repositories you work with regularly: | |
4464 | ||
4465 | ----------------------------------------------- | |
4466 | $ git remote add example git://example.com/project.git | |
4467 | $ git remote # list remote repositories | |
4468 | example | |
4469 | origin | |
4470 | $ git remote show example # get details | |
4471 | * remote example | |
4472 | URL: git://example.com/project.git | |
4473 | Tracked remote branches | |
20244ea2 JS |
4474 | master |
4475 | next | |
4476 | ... | |
2624d9a5 BF |
4477 | $ git fetch example # update branches from example |
4478 | $ git branch -r # list all remote branches | |
4479 | ----------------------------------------------- | |
4480 | ||
4481 | ||
4482 | [[exploring-history]] | |
4483 | Exploring history | |
4484 | ----------------- | |
4485 | ||
4486 | ----------------------------------------------- | |
4487 | $ gitk # visualize and browse history | |
4488 | $ git log # list all commits | |
4489 | $ git log src/ # ...modifying src/ | |
4490 | $ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15 | |
4491 | $ git log master..test # ...in branch test, not in branch master | |
4492 | $ git log test..master # ...in branch master, but not in test | |
4493 | $ git log test...master # ...in one branch, not in both | |
4494 | $ git log -S'foo()' # ...where difference contain "foo()" | |
4495 | $ git log --since="2 weeks ago" | |
4496 | $ git log -p # show patches as well | |
4497 | $ git show # most recent commit | |
4498 | $ git diff v2.6.15..v2.6.16 # diff between two tagged versions | |
4499 | $ git diff v2.6.15..HEAD # diff with current head | |
4500 | $ git grep "foo()" # search working directory for "foo()" | |
4501 | $ git grep v2.6.15 "foo()" # search old tree for "foo()" | |
4502 | $ git show v2.6.15:a.txt # look at old version of a.txt | |
4503 | ----------------------------------------------- | |
4504 | ||
4505 | Search for regressions: | |
4506 | ||
4507 | ----------------------------------------------- | |
4508 | $ git bisect start | |
4509 | $ git bisect bad # current version is bad | |
4510 | $ git bisect good v2.6.13-rc2 # last known good revision | |
4511 | Bisecting: 675 revisions left to test after this | |
4512 | # test here, then: | |
4513 | $ git bisect good # if this revision is good, or | |
4514 | $ git bisect bad # if this revision is bad. | |
4515 | # repeat until done. | |
4516 | ----------------------------------------------- | |
4517 | ||
4518 | [[making-changes]] | |
4519 | Making changes | |
4520 | -------------- | |
4521 | ||
2de9b711 | 4522 | Make sure Git knows who to blame: |
2624d9a5 BF |
4523 | |
4524 | ------------------------------------------------ | |
4525 | $ cat >>~/.gitconfig <<\EOF | |
4526 | [user] | |
4527 | name = Your Name Comes Here | |
4528 | email = you@yourdomain.example.com | |
4529 | EOF | |
4530 | ------------------------------------------------ | |
4531 | ||
4532 | Select file contents to include in the next commit, then make the | |
4533 | commit: | |
4534 | ||
4535 | ----------------------------------------------- | |
4536 | $ git add a.txt # updated file | |
4537 | $ git add b.txt # new file | |
4538 | $ git rm c.txt # old file | |
4539 | $ git commit | |
4540 | ----------------------------------------------- | |
4541 | ||
4542 | Or, prepare and create the commit in one step: | |
4543 | ||
4544 | ----------------------------------------------- | |
4545 | $ git commit d.txt # use latest content only of d.txt | |
4546 | $ git commit -a # use latest content of all tracked files | |
4547 | ----------------------------------------------- | |
4548 | ||
4549 | [[merging]] | |
4550 | Merging | |
4551 | ------- | |
4552 | ||
4553 | ----------------------------------------------- | |
4554 | $ git merge test # merge branch "test" into the current branch | |
4555 | $ git pull git://example.com/project.git master | |
4556 | # fetch and merge in remote branch | |
4557 | $ git pull . test # equivalent to git merge test | |
4558 | ----------------------------------------------- | |
4559 | ||
4560 | [[sharing-your-changes]] | |
4561 | Sharing your changes | |
4562 | -------------------- | |
4563 | ||
4564 | Importing or exporting patches: | |
4565 | ||
4566 | ----------------------------------------------- | |
4567 | $ git format-patch origin..HEAD # format a patch for each commit | |
4568 | # in HEAD but not in origin | |
4569 | $ git am mbox # import patches from the mailbox "mbox" | |
4570 | ----------------------------------------------- | |
4571 | ||
2de9b711 | 4572 | Fetch a branch in a different Git repository, then merge into the |
2624d9a5 BF |
4573 | current branch: |
4574 | ||
4575 | ----------------------------------------------- | |
4576 | $ git pull git://example.com/project.git theirbranch | |
4577 | ----------------------------------------------- | |
4578 | ||
4579 | Store the fetched branch into a local branch before merging into the | |
4580 | current branch: | |
4581 | ||
4582 | ----------------------------------------------- | |
4583 | $ git pull git://example.com/project.git theirbranch:mybranch | |
4584 | ----------------------------------------------- | |
4585 | ||
4586 | After creating commits on a local branch, update the remote | |
4587 | branch with your commits: | |
4588 | ||
4589 | ----------------------------------------------- | |
4590 | $ git push ssh://example.com/project.git mybranch:theirbranch | |
4591 | ----------------------------------------------- | |
4592 | ||
4593 | When remote and local branch are both named "test": | |
4594 | ||
4595 | ----------------------------------------------- | |
4596 | $ git push ssh://example.com/project.git test | |
4597 | ----------------------------------------------- | |
4598 | ||
4599 | Shortcut version for a frequently used remote repository: | |
4600 | ||
4601 | ----------------------------------------------- | |
4602 | $ git remote add example ssh://example.com/project.git | |
4603 | $ git push example test | |
4604 | ----------------------------------------------- | |
4605 | ||
4606 | [[repository-maintenance]] | |
4607 | Repository maintenance | |
4608 | ---------------------- | |
4609 | ||
4610 | Check for corruption: | |
4611 | ||
4612 | ----------------------------------------------- | |
4613 | $ git fsck | |
4614 | ----------------------------------------------- | |
4615 | ||
4616 | Recompress, remove unused cruft: | |
4617 | ||
4618 | ----------------------------------------------- | |
4619 | $ git gc | |
4620 | ----------------------------------------------- | |
4621 | ||
4622 | ||
e34caace | 4623 | [[todo]] |
2624d9a5 BF |
4624 | Appendix B: Notes and todo list for this manual |
4625 | =============================================== | |
6bd9b682 BF |
4626 | |
4627 | This is a work in progress. | |
4628 | ||
4629 | The basic requirements: | |
ecd95b53 BF |
4630 | |
4631 | - It must be readable in order, from beginning to end, by someone | |
4632 | intelligent with a basic grasp of the UNIX command line, but without | |
2de9b711 | 4633 | any special knowledge of Git. If necessary, any other prerequisites |
ecd95b53 BF |
4634 | should be specifically mentioned as they arise. |
4635 | - Whenever possible, section headings should clearly describe the task | |
4636 | they explain how to do, in language that requires no more knowledge | |
4637 | than necessary: for example, "importing patches into a project" rather | |
6127c086 | 4638 | than "the `git am` command" |
6bd9b682 | 4639 | |
d5cd5de4 BF |
4640 | Think about how to create a clear chapter dependency graph that will |
4641 | allow people to get to important topics without necessarily reading | |
4642 | everything in between. | |
d19fbc3c | 4643 | |
1249d8ad | 4644 | Scan `Documentation/` for other stuff left out; in particular: |
ecd95b53 BF |
4645 | |
4646 | - howto's | |
1249d8ad | 4647 | - some of `technical/`? |
ecd95b53 | 4648 | - hooks |
5162e697 | 4649 | - list of commands in linkgit:git[1] |
d19fbc3c BF |
4650 | |
4651 | Scan email archives for other stuff left out | |
4652 | ||
4653 | Scan man pages to see if any assume more background than this manual | |
4654 | provides. | |
4655 | ||
2f99710c | 4656 | Simplify beginning by suggesting disconnected head instead of |
b181d57f | 4657 | temporary branch creation? |
d19fbc3c | 4658 | |
2f99710c BF |
4659 | Add more good examples. Entire sections of just cookbook examples |
4660 | might be a good idea; maybe make an "advanced examples" section a | |
4661 | standard end-of-chapter section? | |
d19fbc3c BF |
4662 | |
4663 | Include cross-references to the glossary, where appropriate. | |
4664 | ||
9a241220 BF |
4665 | Document shallow clones? See draft 1.5.0 release notes for some |
4666 | documentation. | |
4667 | ||
3dff5379 | 4668 | Add a section on working with other version control systems, including |
9a241220 BF |
4669 | CVS, Subversion, and just imports of series of release tarballs. |
4670 | ||
a8cd1402 | 4671 | More details on gitweb? |
0b375ab0 BF |
4672 | |
4673 | Write a chapter on using plumbing and writing scripts. | |
d9bd321c BF |
4674 | |
4675 | Alternates, clone -reference, etc. | |
4676 | ||
1cdade2c | 4677 | More on recovery from repository corruption. See: |
efe6de6e OB |
4678 | http://marc.info/?l=git&m=117263864820799&w=2 |
4679 | http://marc.info/?l=git&m=117147855503798&w=2 |