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1 | Git User's Manual |
2 | _________________ | |
3 | ||
4 | This manual is designed to be readable by someone with basic unix | |
5 | commandline skills, but no previous knowledge of git. | |
6 | ||
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7 | Chapters 1 and 2 explain how to fetch and study a project using |
8 | git--the tools you'd need to build and test a particular version of a | |
9 | software project, to search for regressions, and so on. | |
6bd9b682 | 10 | |
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11 | Chapter 3 explains how to do development with git, and chapter 4 how |
12 | to share that development with others. | |
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13 | |
14 | Further chapters cover more specialized topics. | |
15 | ||
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16 | Comprehensive reference documentation is available through the man |
17 | pages. For a command such as "git clone", just use | |
18 | ||
19 | ------------------------------------------------ | |
20 | $ man git-clone | |
21 | ------------------------------------------------ | |
22 | ||
23 | Repositories and Branches | |
24 | ========================= | |
25 | ||
26 | How to get a git repository | |
27 | --------------------------- | |
28 | ||
29 | It will be useful to have a git repository to experiment with as you | |
30 | read this manual. | |
31 | ||
32 | The best way to get one is by using the gitlink:git-clone[1] command | |
33 | to download a copy of an existing repository for a project that you | |
34 | are interested in. If you don't already have a project in mind, here | |
35 | are some interesting examples: | |
36 | ||
37 | ------------------------------------------------ | |
38 | # git itself (approx. 10MB download): | |
39 | $ git clone git://git.kernel.org/pub/scm/git/git.git | |
40 | # the linux kernel (approx. 150MB download): | |
41 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git | |
42 | ------------------------------------------------ | |
43 | ||
44 | The initial clone may be time-consuming for a large project, but you | |
45 | will only need to clone once. | |
46 | ||
47 | The clone command creates a new directory named after the project | |
48 | ("git" or "linux-2.6" in the examples above). After you cd into this | |
49 | directory, you will see that it contains a copy of the project files, | |
50 | together with a special top-level directory named ".git", which | |
51 | contains all the information about the history of the project. | |
52 | ||
d5cd5de4 | 53 | In most of the following, examples will be taken from one of the two |
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54 | repositories above. |
55 | ||
56 | How to check out a different version of a project | |
57 | ------------------------------------------------- | |
58 | ||
59 | Git is best thought of as a tool for storing the history of a | |
60 | collection of files. It stores the history as a compressed | |
61 | collection of interrelated snapshots (versions) of the project's | |
62 | contents. | |
63 | ||
64 | A single git repository may contain multiple branches. Each branch | |
65 | is a bookmark referencing a particular point in the project history. | |
66 | The gitlink:git-branch[1] command shows you the list of branches: | |
67 | ||
68 | ------------------------------------------------ | |
69 | $ git branch | |
70 | * master | |
71 | ------------------------------------------------ | |
72 | ||
73 | A freshly cloned repository contains a single branch, named "master", | |
74 | and the working directory contains the version of the project | |
75 | referred to by the master branch. | |
76 | ||
77 | Most projects also use tags. Tags, like branches, are references | |
78 | into the project's history, and can be listed using the | |
79 | gitlink:git-tag[1] command: | |
80 | ||
81 | ------------------------------------------------ | |
82 | $ git tag -l | |
83 | v2.6.11 | |
84 | v2.6.11-tree | |
85 | v2.6.12 | |
86 | v2.6.12-rc2 | |
87 | v2.6.12-rc3 | |
88 | v2.6.12-rc4 | |
89 | v2.6.12-rc5 | |
90 | v2.6.12-rc6 | |
91 | v2.6.13 | |
92 | ... | |
93 | ------------------------------------------------ | |
94 | ||
95 | Create a new branch pointing to one of these versions and check it | |
96 | out using gitlink:git-checkout[1]: | |
97 | ||
98 | ------------------------------------------------ | |
99 | $ git checkout -b new v2.6.13 | |
100 | ------------------------------------------------ | |
101 | ||
102 | The working directory then reflects the contents that the project had | |
103 | when it was tagged v2.6.13, and gitlink:git-branch[1] shows two | |
104 | branches, with an asterisk marking the currently checked-out branch: | |
105 | ||
106 | ------------------------------------------------ | |
107 | $ git branch | |
108 | master | |
109 | * new | |
110 | ------------------------------------------------ | |
111 | ||
112 | If you decide that you'd rather see version 2.6.17, you can modify | |
113 | the current branch to point at v2.6.17 instead, with | |
114 | ||
115 | ------------------------------------------------ | |
116 | $ git reset --hard v2.6.17 | |
117 | ------------------------------------------------ | |
118 | ||
119 | Note that if the current branch was your only reference to a | |
120 | particular point in history, then resetting that branch may leave you | |
121 | with no way to find the history it used to point to; so use this | |
122 | command carefully. | |
123 | ||
124 | Understanding History: Commits | |
125 | ------------------------------ | |
126 | ||
127 | Every change in the history of a project is represented by a commit. | |
128 | The gitlink:git-show[1] command shows the most recent commit on the | |
129 | current branch: | |
130 | ||
131 | ------------------------------------------------ | |
132 | $ git show | |
133 | commit 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2 | |
134 | Author: Jamal Hadi Salim <hadi@cyberus.ca> | |
135 | Date: Sat Dec 2 22:22:25 2006 -0800 | |
136 | ||
137 | [XFRM]: Fix aevent structuring to be more complete. | |
138 | ||
139 | aevents can not uniquely identify an SA. We break the ABI with this | |
140 | patch, but consensus is that since it is not yet utilized by any | |
141 | (known) application then it is fine (better do it now than later). | |
142 | ||
143 | Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca> | |
144 | Signed-off-by: David S. Miller <davem@davemloft.net> | |
145 | ||
146 | diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt | |
147 | index 8be626f..d7aac9d 100644 | |
148 | --- a/Documentation/networking/xfrm_sync.txt | |
149 | +++ b/Documentation/networking/xfrm_sync.txt | |
150 | @@ -47,10 +47,13 @@ aevent_id structure looks like: | |
151 | ||
152 | struct xfrm_aevent_id { | |
153 | struct xfrm_usersa_id sa_id; | |
154 | + xfrm_address_t saddr; | |
155 | __u32 flags; | |
156 | + __u32 reqid; | |
157 | }; | |
158 | ... | |
159 | ------------------------------------------------ | |
160 | ||
161 | As you can see, a commit shows who made the latest change, what they | |
162 | did, and why. | |
163 | ||
eb6ae7f4 | 164 | Every commit has a 40-hexdigit id, sometimes called the "SHA1 id", shown |
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165 | on the first line of the "git show" output. You can usually refer to |
166 | a commit by a shorter name, such as a tag or a branch name, but this | |
167 | longer id can also be useful. In particular, it is a globally unique | |
168 | name for this commit: so if you tell somebody else the SHA1 id (for | |
169 | example in email), then you are guaranteed they will see the same | |
170 | commit in their repository that you do in yours. | |
171 | ||
172 | Understanding history: commits, parents, and reachability | |
173 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
174 | ||
175 | Every commit (except the very first commit in a project) also has a | |
176 | parent commit which shows what happened before this commit. | |
177 | Following the chain of parents will eventually take you back to the | |
178 | beginning of the project. | |
179 | ||
180 | However, the commits do not form a simple list; git allows lines of | |
181 | development to diverge and then reconverge, and the point where two | |
182 | lines of development reconverge is called a "merge". The commit | |
183 | representing a merge can therefore have more than one parent, with | |
184 | each parent representing the most recent commit on one of the lines | |
185 | of development leading to that point. | |
186 | ||
187 | The best way to see how this works is using the gitlink:gitk[1] | |
188 | command; running gitk now on a git repository and looking for merge | |
189 | commits will help understand how the git organizes history. | |
190 | ||
191 | In the following, we say that commit X is "reachable" from commit Y | |
192 | if commit X is an ancestor of commit Y. Equivalently, you could say | |
193 | that Y is a descendent of X, or that there is a chain of parents | |
194 | leading from commit Y to commit X. | |
195 | ||
196 | Undestanding history: History diagrams | |
197 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
198 | ||
199 | We will sometimes represent git history using diagrams like the one | |
200 | below. Commits are shown as "o", and the links between them with | |
201 | lines drawn with - / and \. Time goes left to right: | |
202 | ||
203 | o--o--o <-- Branch A | |
204 | / | |
205 | o--o--o <-- master | |
206 | \ | |
207 | o--o--o <-- Branch B | |
208 | ||
209 | If we need to talk about a particular commit, the character "o" may | |
210 | be replaced with another letter or number. | |
211 | ||
212 | Understanding history: What is a branch? | |
213 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
214 | ||
215 | Though we've been using the word "branch" to mean a kind of reference | |
216 | to a particular commit, the word branch is also commonly used to | |
217 | refer to the line of commits leading up to that point. In the | |
218 | example above, git may think of the branch named "A" as just a | |
219 | pointer to one particular commit, but we may refer informally to the | |
220 | line of three commits leading up to that point as all being part of | |
221 | "branch A". | |
222 | ||
223 | If we need to make it clear that we're just talking about the most | |
224 | recent commit on the branch, we may refer to that commit as the | |
225 | "head" of the branch. | |
226 | ||
227 | Manipulating branches | |
228 | --------------------- | |
229 | ||
230 | Creating, deleting, and modifying branches is quick and easy; here's | |
231 | a summary of the commands: | |
232 | ||
233 | git branch:: | |
234 | list all branches | |
235 | git branch <branch>:: | |
236 | create a new branch named <branch>, referencing the same | |
237 | point in history as the current branch | |
238 | git branch <branch> <start-point>:: | |
239 | create a new branch named <branch>, referencing | |
240 | <start-point>, which may be specified any way you like, | |
241 | including using a branch name or a tag name | |
242 | git branch -d <branch>:: | |
243 | delete the branch <branch>; if the branch you are deleting | |
244 | points to a commit which is not reachable from this branch, | |
245 | this command will fail with a warning. | |
246 | git branch -D <branch>:: | |
247 | even if the branch points to a commit not reachable | |
248 | from the current branch, you may know that that commit | |
249 | is still reachable from some other branch or tag. In that | |
250 | case it is safe to use this command to force git to delete | |
251 | the branch. | |
252 | git checkout <branch>:: | |
253 | make the current branch <branch>, updating the working | |
254 | directory to reflect the version referenced by <branch> | |
255 | git checkout -b <new> <start-point>:: | |
256 | create a new branch <new> referencing <start-point>, and | |
257 | check it out. | |
258 | ||
259 | It is also useful to know that the special symbol "HEAD" can always | |
260 | be used to refer to the current branch. | |
261 | ||
262 | Examining branches from a remote repository | |
263 | ------------------------------------------- | |
264 | ||
265 | The "master" branch that was created at the time you cloned is a copy | |
266 | of the HEAD in the repository that you cloned from. That repository | |
267 | may also have had other branches, though, and your local repository | |
268 | keeps branches which track each of those remote branches, which you | |
269 | can view using the "-r" option to gitlink:git-branch[1]: | |
270 | ||
271 | ------------------------------------------------ | |
272 | $ git branch -r | |
273 | origin/HEAD | |
274 | origin/html | |
275 | origin/maint | |
276 | origin/man | |
277 | origin/master | |
278 | origin/next | |
279 | origin/pu | |
280 | origin/todo | |
281 | ------------------------------------------------ | |
282 | ||
283 | You cannot check out these remote-tracking branches, but you can | |
284 | examine them on a branch of your own, just as you would a tag: | |
285 | ||
286 | ------------------------------------------------ | |
287 | $ git checkout -b my-todo-copy origin/todo | |
288 | ------------------------------------------------ | |
289 | ||
290 | Note that the name "origin" is just the name that git uses by default | |
291 | to refer to the repository that you cloned from. | |
292 | ||
293 | [[how-git-stores-references]] | |
294 | How git stores references | |
295 | ------------------------- | |
296 | ||
297 | Branches, remote-tracking branches, and tags are all references to | |
298 | commits. Git stores these references in the ".git" directory. Most | |
299 | of them are stored in .git/refs/: | |
300 | ||
301 | - branches are stored in .git/refs/heads | |
302 | - tags are stored in .git/refs/tags | |
303 | - remote-tracking branches for "origin" are stored in | |
304 | .git/refs/remotes/origin/ | |
305 | ||
306 | If you look at one of these files you will see that they usually | |
307 | contain just the SHA1 id of a commit: | |
308 | ||
309 | ------------------------------------------------ | |
310 | $ ls .git/refs/heads/ | |
311 | master | |
312 | $ cat .git/refs/heads/master | |
313 | c0f982dcf188d55db9d932a39d4ea7becaa55fed | |
314 | ------------------------------------------------ | |
315 | ||
316 | You can refer to a reference by its path relative to the .git | |
317 | directory. However, we've seen above that git will also accept | |
318 | shorter names; for example, "master" is an acceptable shortcut for | |
319 | "refs/heads/master", and "origin/master" is a shortcut for | |
320 | "refs/remotes/origin/master". | |
321 | ||
322 | As another useful shortcut, you can also refer to the "HEAD" of | |
323 | "origin" (or any other remote), using just the name of the remote. | |
324 | ||
325 | For the complete list of paths which git checks for references, and | |
326 | how it decides which to choose when there are multiple references | |
327 | with the same name, see the "SPECIFYING REVISIONS" section of | |
328 | gitlink:git-rev-parse[1]. | |
329 | ||
330 | [[Updating-a-repository-with-git-fetch]] | |
331 | Updating a repository with git fetch | |
332 | ------------------------------------ | |
333 | ||
334 | Eventually the developer cloned from will do additional work in her | |
335 | repository, creating new commits and advancing the branches to point | |
336 | at the new commits. | |
337 | ||
338 | The command "git fetch", with no arguments, will update all of the | |
339 | remote-tracking branches to the latest version found in her | |
340 | repository. It will not touch any of your own branches--not even the | |
341 | "master" branch that was created for you on clone. | |
342 | ||
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343 | Fetching branches from other repositories |
344 | ----------------------------------------- | |
345 | ||
346 | You can also track branches from repositories other than the one you | |
347 | cloned from, using gitlink:git-remote[1]: | |
348 | ||
349 | ------------------------------------------------- | |
350 | $ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git | |
351 | $ git fetch | |
352 | * refs/remotes/linux-nfs/master: storing branch 'master' ... | |
353 | commit: bf81b46 | |
354 | ------------------------------------------------- | |
355 | ||
356 | New remote-tracking branches will be stored under the shorthand name | |
357 | that you gave "git remote add", in this case linux-nfs: | |
358 | ||
359 | ------------------------------------------------- | |
360 | $ git branch -r | |
361 | linux-nfs/master | |
362 | origin/master | |
363 | ------------------------------------------------- | |
364 | ||
365 | If you run "git fetch <remote>" later, the tracking branches for the | |
366 | named <remote> will be updated. | |
367 | ||
368 | If you examine the file .git/config, you will see that git has added | |
369 | a new stanza: | |
370 | ||
371 | ------------------------------------------------- | |
372 | $ cat .git/config | |
373 | ... | |
374 | [remote "linux-nfs"] | |
375 | url = git://linux-nfs.org/~bfields/git.git | |
376 | fetch = +refs/heads/*:refs/remotes/linux-nfs-read/* | |
377 | ... | |
378 | ------------------------------------------------- | |
379 | ||
380 | This is what causes git to track the remote's branches; you may | |
381 | modify or delete these configuration options by editing .git/config | |
382 | with a text editor. | |
383 | ||
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384 | Fetching individual branches |
385 | ---------------------------- | |
386 | ||
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387 | TODO: find another home for this, later on: |
388 | ||
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389 | You can also choose to update just one branch at a time: |
390 | ||
391 | ------------------------------------------------- | |
392 | $ git fetch origin todo:refs/remotes/origin/todo | |
393 | ------------------------------------------------- | |
394 | ||
395 | The first argument, "origin", just tells git to fetch from the | |
396 | repository you originally cloned from. The second argument tells git | |
397 | to fetch the branch named "todo" from the remote repository, and to | |
398 | store it locally under the name refs/remotes/origin/todo; as we saw | |
399 | above, remote-tracking branches are stored under | |
400 | refs/remotes/<name-of-repository>/<name-of-branch>. | |
401 | ||
402 | You can also fetch branches from other repositories; so | |
403 | ||
404 | ------------------------------------------------- | |
405 | $ git fetch git://example.com/proj.git master:refs/remotes/example/master | |
406 | ------------------------------------------------- | |
407 | ||
408 | will create a new reference named "refs/remotes/example/master" and | |
409 | store in it the branch named "master" from the repository at the | |
410 | given URL. If you already have a branch named | |
411 | "refs/remotes/example/master", it will attempt to "fast-forward" to | |
412 | the commit given by example.com's master branch. So next we explain | |
413 | what a fast-forward is: | |
414 | ||
415 | [[fast-forwards]] | |
416 | Understanding git history: fast-forwards | |
417 | ---------------------------------------- | |
418 | ||
419 | In the previous example, when updating an existing branch, "git | |
420 | fetch" checks to make sure that the most recent commit on the remote | |
421 | branch is a descendant of the most recent commit on your copy of the | |
422 | branch before updating your copy of the branch to point at the new | |
423 | commit. Git calls this process a "fast forward". | |
424 | ||
425 | A fast forward looks something like this: | |
426 | ||
427 | o--o--o--o <-- old head of the branch | |
428 | \ | |
429 | o--o--o <-- new head of the branch | |
430 | ||
431 | ||
432 | In some cases it is possible that the new head will *not* actually be | |
433 | a descendant of the old head. For example, the developer may have | |
434 | realized she made a serious mistake, and decided to backtrack, | |
435 | resulting in a situation like: | |
436 | ||
437 | o--o--o--o--a--b <-- old head of the branch | |
438 | \ | |
439 | o--o--o <-- new head of the branch | |
440 | ||
441 | ||
442 | ||
443 | In this case, "git fetch" will fail, and print out a warning. | |
444 | ||
445 | In that case, you can still force git to update to the new head, as | |
446 | described in the following section. However, note that in the | |
447 | situation above this may mean losing the commits labeled "a" and "b", | |
448 | unless you've already created a reference of your own pointing to | |
449 | them. | |
450 | ||
451 | Forcing git fetch to do non-fast-forward updates | |
452 | ------------------------------------------------ | |
453 | ||
454 | If git fetch fails because the new head of a branch is not a | |
455 | descendant of the old head, you may force the update with: | |
456 | ||
457 | ------------------------------------------------- | |
458 | $ git fetch git://example.com/proj.git +master:refs/remotes/example/master | |
459 | ------------------------------------------------- | |
460 | ||
461 | Note the addition of the "+" sign. Be aware that commits which the | |
462 | old version of example/master pointed at may be lost, as we saw in | |
463 | the previous section. | |
464 | ||
465 | Configuring remote branches | |
466 | --------------------------- | |
467 | ||
468 | We saw above that "origin" is just a shortcut to refer to the | |
469 | repository which you originally cloned from. This information is | |
470 | stored in git configuration variables, which you can see using | |
471 | gitlink:git-repo-config[1]: | |
472 | ||
473 | ------------------------------------------------- | |
474 | $ git-repo-config -l | |
475 | core.repositoryformatversion=0 | |
476 | core.filemode=true | |
477 | core.logallrefupdates=true | |
478 | remote.origin.url=git://git.kernel.org/pub/scm/git/git.git | |
479 | remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* | |
480 | branch.master.remote=origin | |
481 | branch.master.merge=refs/heads/master | |
482 | ------------------------------------------------- | |
483 | ||
484 | If there are other repositories that you also use frequently, you can | |
485 | create similar configuration options to save typing; for example, | |
486 | after | |
487 | ||
488 | ------------------------------------------------- | |
eb6ae7f4 | 489 | $ git repo-config remote.example.url git://example.com/proj.git |
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490 | ------------------------------------------------- |
491 | ||
492 | then the following two commands will do the same thing: | |
493 | ||
494 | ------------------------------------------------- | |
495 | $ git fetch git://example.com/proj.git master:refs/remotes/example/master | |
496 | $ git fetch example master:refs/remotes/example/master | |
497 | ------------------------------------------------- | |
498 | ||
499 | Even better, if you add one more option: | |
500 | ||
501 | ------------------------------------------------- | |
eb6ae7f4 | 502 | $ git repo-config remote.example.fetch master:refs/remotes/example/master |
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503 | ------------------------------------------------- |
504 | ||
505 | then the following commands will all do the same thing: | |
506 | ||
507 | ------------------------------------------------- | |
508 | $ git fetch git://example.com/proj.git master:ref/remotes/example/master | |
509 | $ git fetch example master:ref/remotes/example/master | |
510 | $ git fetch example example/master | |
511 | $ git fetch example | |
512 | ------------------------------------------------- | |
513 | ||
514 | You can also add a "+" to force the update each time: | |
515 | ||
516 | ------------------------------------------------- | |
eb6ae7f4 | 517 | $ git repo-config remote.example.fetch +master:ref/remotes/example/master |
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518 | ------------------------------------------------- |
519 | ||
520 | Don't do this unless you're sure you won't mind "git fetch" possibly | |
521 | throwing away commits on mybranch. | |
522 | ||
523 | Also note that all of the above configuration can be performed by | |
524 | directly editing the file .git/config instead of using | |
525 | gitlink:git-repo-config[1]. | |
526 | ||
527 | See gitlink:git-repo-config[1] for more details on the configuration | |
528 | options mentioned above. | |
529 | ||
530 | Exploring git history | |
531 | ===================== | |
532 | ||
533 | Git is best thought of as a tool for storing the history of a | |
534 | collection of files. It does this by storing compressed snapshots of | |
535 | the contents of a file heirarchy, together with "commits" which show | |
536 | the relationships between these snapshots. | |
537 | ||
538 | Git provides extremely flexible and fast tools for exploring the | |
539 | history of a project. | |
540 | ||
541 | We start with one specialized tool which is useful for finding the | |
542 | commit that introduced a bug into a project. | |
543 | ||
544 | How to use bisect to find a regression | |
545 | -------------------------------------- | |
546 | ||
547 | Suppose version 2.6.18 of your project worked, but the version at | |
548 | "master" crashes. Sometimes the best way to find the cause of such a | |
549 | regression is to perform a brute-force search through the project's | |
550 | history to find the particular commit that caused the problem. The | |
551 | gitlink:git-bisect[1] command can help you do this: | |
552 | ||
553 | ------------------------------------------------- | |
554 | $ git bisect start | |
555 | $ git bisect good v2.6.18 | |
556 | $ git bisect bad master | |
557 | Bisecting: 3537 revisions left to test after this | |
558 | [65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6] | |
559 | ------------------------------------------------- | |
560 | ||
561 | If you run "git branch" at this point, you'll see that git has | |
562 | temporarily moved you to a new branch named "bisect". This branch | |
563 | points to a commit (with commit id 65934...) that is reachable from | |
564 | v2.6.19 but not from v2.6.18. Compile and test it, and see whether | |
565 | it crashes. Assume it does crash. Then: | |
566 | ||
567 | ------------------------------------------------- | |
568 | $ git bisect bad | |
569 | Bisecting: 1769 revisions left to test after this | |
570 | [7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings | |
571 | ------------------------------------------------- | |
572 | ||
573 | checks out an older version. Continue like this, telling git at each | |
574 | stage whether the version it gives you is good or bad, and notice | |
575 | that the number of revisions left to test is cut approximately in | |
576 | half each time. | |
577 | ||
578 | After about 13 tests (in this case), it will output the commit id of | |
579 | the guilty commit. You can then examine the commit with | |
580 | gitlink:git-show[1], find out who wrote it, and mail them your bug | |
581 | report with the commit id. Finally, run | |
582 | ||
583 | ------------------------------------------------- | |
584 | $ git bisect reset | |
585 | ------------------------------------------------- | |
586 | ||
587 | to return you to the branch you were on before and delete the | |
588 | temporary "bisect" branch. | |
589 | ||
590 | Note that the version which git-bisect checks out for you at each | |
591 | point is just a suggestion, and you're free to try a different | |
592 | version if you think it would be a good idea. For example, | |
593 | occasionally you may land on a commit that broke something unrelated; | |
594 | run | |
595 | ||
596 | ------------------------------------------------- | |
597 | $ git bisect-visualize | |
598 | ------------------------------------------------- | |
599 | ||
600 | which will run gitk and label the commit it chose with a marker that | |
601 | says "bisect". Chose a safe-looking commit nearby, note its commit | |
602 | id, and check it out with: | |
603 | ||
604 | ------------------------------------------------- | |
605 | $ git reset --hard fb47ddb2db... | |
606 | ------------------------------------------------- | |
607 | ||
608 | then test, run "bisect good" or "bisect bad" as appropriate, and | |
609 | continue. | |
610 | ||
611 | Naming commits | |
612 | -------------- | |
613 | ||
614 | We have seen several ways of naming commits already: | |
615 | ||
eb6ae7f4 | 616 | - 40-hexdigit SHA1 id |
d19fbc3c BF |
617 | - branch name: refers to the commit at the head of the given |
618 | branch | |
619 | - tag name: refers to the commit pointed to by the given tag | |
620 | (we've seen branches and tags are special cases of | |
621 | <<how-git-stores-references,references>>). | |
622 | - HEAD: refers to the head of the current branch | |
623 | ||
eb6ae7f4 | 624 | There are many more; see the "SPECIFYING REVISIONS" section of the |
aec053bb | 625 | gitlink:git-rev-parse[1] man page for the complete list of ways to |
d19fbc3c BF |
626 | name revisions. Some examples: |
627 | ||
628 | ------------------------------------------------- | |
629 | $ git show fb47ddb2 # the first few characters of the SHA1 id | |
630 | # are usually enough to specify it uniquely | |
631 | $ git show HEAD^ # the parent of the HEAD commit | |
632 | $ git show HEAD^^ # the grandparent | |
633 | $ git show HEAD~4 # the great-great-grandparent | |
634 | ------------------------------------------------- | |
635 | ||
636 | Recall that merge commits may have more than one parent; by default, | |
637 | ^ and ~ follow the first parent listed in the commit, but you can | |
638 | also choose: | |
639 | ||
640 | ------------------------------------------------- | |
641 | $ git show HEAD^1 # show the first parent of HEAD | |
642 | $ git show HEAD^2 # show the second parent of HEAD | |
643 | ------------------------------------------------- | |
644 | ||
645 | In addition to HEAD, there are several other special names for | |
646 | commits: | |
647 | ||
648 | Merges (to be discussed later), as well as operations such as | |
649 | git-reset, which change the currently checked-out commit, generally | |
650 | set ORIG_HEAD to the value HEAD had before the current operation. | |
651 | ||
652 | The git-fetch operation always stores the head of the last fetched | |
653 | branch in FETCH_HEAD. For example, if you run git fetch without | |
654 | specifying a local branch as the target of the operation | |
655 | ||
656 | ------------------------------------------------- | |
657 | $ git fetch git://example.com/proj.git theirbranch | |
658 | ------------------------------------------------- | |
659 | ||
660 | the fetched commits will still be available from FETCH_HEAD. | |
661 | ||
662 | When we discuss merges we'll also see the special name MERGE_HEAD, | |
663 | which refers to the other branch that we're merging in to the current | |
664 | branch. | |
665 | ||
aec053bb BF |
666 | The gitlink:git-rev-parse[1] command is a low-level command that is |
667 | occasionally useful for translating some name for a commit to the SHA1 id for | |
668 | that commit: | |
669 | ||
670 | ------------------------------------------------- | |
671 | $ git rev-parse origin | |
672 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
673 | ------------------------------------------------- | |
674 | ||
d19fbc3c BF |
675 | Creating tags |
676 | ------------- | |
677 | ||
678 | We can also create a tag to refer to a particular commit; after | |
679 | running | |
680 | ||
681 | ------------------------------------------------- | |
682 | $ git-tag stable-1 1b2e1d63ff | |
683 | ------------------------------------------------- | |
684 | ||
685 | You can use stable-1 to refer to the commit 1b2e1d63ff. | |
686 | ||
687 | This creates a "lightweight" tag. If the tag is a tag you wish to | |
688 | share with others, and possibly sign cryptographically, then you | |
689 | should create a tag object instead; see the gitlink:git-tag[1] man | |
690 | page for details. | |
691 | ||
692 | Browsing revisions | |
693 | ------------------ | |
694 | ||
695 | The gitlink:git-log[1] command can show lists of commits. On its | |
696 | own, it shows all commits reachable from the parent commit; but you | |
697 | can also make more specific requests: | |
698 | ||
699 | ------------------------------------------------- | |
700 | $ git log v2.5.. # commits since (not reachable from) v2.5 | |
701 | $ git log test..master # commits reachable from master but not test | |
702 | $ git log master..test # ...reachable from test but not master | |
703 | $ git log master...test # ...reachable from either test or master, | |
704 | # but not both | |
705 | $ git log --since="2 weeks ago" # commits from the last 2 weeks | |
706 | $ git log Makefile # commits which modify Makefile | |
707 | $ git log fs/ # ... which modify any file under fs/ | |
708 | $ git log -S'foo()' # commits which add or remove any file data | |
709 | # matching the string 'foo()' | |
710 | ------------------------------------------------- | |
711 | ||
712 | And of course you can combine all of these; the following finds | |
713 | commits since v2.5 which touch the Makefile or any file under fs: | |
714 | ||
715 | ------------------------------------------------- | |
716 | $ git log v2.5.. Makefile fs/ | |
717 | ------------------------------------------------- | |
718 | ||
719 | You can also ask git log to show patches: | |
720 | ||
721 | ------------------------------------------------- | |
722 | $ git log -p | |
723 | ------------------------------------------------- | |
724 | ||
725 | See the "--pretty" option in the gitlink:git-log[1] man page for more | |
726 | display options. | |
727 | ||
728 | Note that git log starts with the most recent commit and works | |
729 | backwards through the parents; however, since git history can contain | |
730 | multiple independant lines of development, the particular order that | |
731 | commits are listed in may be somewhat arbitrary. | |
732 | ||
733 | Generating diffs | |
734 | ---------------- | |
735 | ||
736 | You can generate diffs between any two versions using | |
737 | gitlink:git-diff[1]: | |
738 | ||
739 | ------------------------------------------------- | |
740 | $ git diff master..test | |
741 | ------------------------------------------------- | |
742 | ||
743 | Sometimes what you want instead is a set of patches: | |
744 | ||
745 | ------------------------------------------------- | |
746 | $ git format-patch master..test | |
747 | ------------------------------------------------- | |
748 | ||
749 | will generate a file with a patch for each commit reachable from test | |
750 | but not from master. Note that if master also has commits which are | |
751 | not reachable from test, then the combined result of these patches | |
752 | will not be the same as the diff produced by the git-diff example. | |
753 | ||
754 | Viewing old file versions | |
755 | ------------------------- | |
756 | ||
757 | You can always view an old version of a file by just checking out the | |
758 | correct revision first. But sometimes it is more convenient to be | |
759 | able to view an old version of a single file without checking | |
760 | anything out; this command does that: | |
761 | ||
762 | ------------------------------------------------- | |
763 | $ git show v2.5:fs/locks.c | |
764 | ------------------------------------------------- | |
765 | ||
766 | Before the colon may be anything that names a commit, and after it | |
767 | may be any path to a file tracked by git. | |
768 | ||
aec053bb BF |
769 | Examples |
770 | -------- | |
771 | ||
772 | Check whether two branches point at the same history | |
773 | ---------------------------------------------------- | |
774 | ||
775 | Suppose you want to check whether two branches point at the same point | |
776 | in history. | |
777 | ||
778 | ------------------------------------------------- | |
779 | $ git diff origin..master | |
780 | ------------------------------------------------- | |
781 | ||
782 | will tell you whether the contents of the project are the same at the two | |
783 | branches; in theory, however, it's possible that the same project contents | |
784 | could have been arrived at by two different historical routes. You could | |
785 | compare the SHA1 id's: | |
786 | ||
787 | ------------------------------------------------- | |
788 | $ git rev-list origin | |
789 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
790 | $ git rev-list master | |
791 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
792 | ------------------------------------------------- | |
793 | ||
794 | Or you could recall that the ... operator selects all commits contained | |
795 | reachable from either one reference or the other but not both: so | |
796 | ||
797 | ------------------------------------------------- | |
798 | $ git log origin...master | |
799 | ------------------------------------------------- | |
800 | ||
801 | will return no commits when the two branches are equal. | |
802 | ||
803 | Check which tagged version a given fix was first included in | |
804 | ------------------------------------------------------------ | |
805 | ||
806 | Suppose you know that a critical fix made it into the linux kernel with commit | |
807 | e05db0fd... You'd like to find which kernel version that commit first made it | |
808 | into. | |
809 | ||
d19fbc3c BF |
810 | Developing with git |
811 | =================== | |
812 | ||
813 | Telling git your name | |
814 | --------------------- | |
815 | ||
816 | Before creating any commits, you should introduce yourself to git. The | |
817 | easiest way to do so is: | |
818 | ||
819 | ------------------------------------------------ | |
820 | $ cat >~/.gitconfig <<\EOF | |
821 | [user] | |
822 | name = Your Name Comes Here | |
823 | email = you@yourdomain.example.com | |
824 | EOF | |
825 | ------------------------------------------------ | |
826 | ||
827 | ||
828 | Creating a new repository | |
829 | ------------------------- | |
830 | ||
831 | Creating a new repository from scratch is very easy: | |
832 | ||
833 | ------------------------------------------------- | |
834 | $ mkdir project | |
835 | $ cd project | |
836 | $ git init-db | |
837 | ------------------------------------------------- | |
838 | ||
839 | If you have some initial content (say, a tarball): | |
840 | ||
841 | ------------------------------------------------- | |
842 | $ tar -xzvf project.tar.gz | |
843 | $ cd project | |
844 | $ git init-db | |
845 | $ git add . # include everything below ./ in the first commit: | |
846 | $ git commit | |
847 | ------------------------------------------------- | |
848 | ||
849 | [[how-to-make-a-commit]] | |
850 | how to make a commit | |
851 | -------------------- | |
852 | ||
853 | Creating a new commit takes three steps: | |
854 | ||
855 | 1. Making some changes to the working directory using your | |
856 | favorite editor. | |
857 | 2. Telling git about your changes. | |
858 | 3. Creating the commit using the content you told git about | |
859 | in step 2. | |
860 | ||
861 | In practice, you can interleave and repeat steps 1 and 2 as many | |
862 | times as you want: in order to keep track of what you want committed | |
863 | at step 3, git maintains a snapshot of the tree's contents in a | |
864 | special staging area called "the index." | |
865 | ||
01997b4a BF |
866 | At the beginning, the content of the index will be identical to |
867 | that of the HEAD. The command "git diff --cached", which shows | |
868 | the difference between the HEAD and the index, should therefore | |
869 | produce no output at that point. | |
eb6ae7f4 | 870 | |
d19fbc3c BF |
871 | Modifying the index is easy: |
872 | ||
873 | To update the index with the new contents of a modified file, use | |
874 | ||
875 | ------------------------------------------------- | |
876 | $ git add path/to/file | |
877 | ------------------------------------------------- | |
878 | ||
879 | To add the contents of a new file to the index, use | |
880 | ||
881 | ------------------------------------------------- | |
882 | $ git add path/to/file | |
883 | ------------------------------------------------- | |
884 | ||
eb6ae7f4 | 885 | To remove a file from the index and from the working tree, |
d19fbc3c BF |
886 | |
887 | ------------------------------------------------- | |
888 | $ git rm path/to/file | |
889 | ------------------------------------------------- | |
890 | ||
891 | After each step you can verify that | |
892 | ||
893 | ------------------------------------------------- | |
894 | $ git diff --cached | |
895 | ------------------------------------------------- | |
896 | ||
897 | always shows the difference between the HEAD and the index file--this | |
898 | is what you'd commit if you created the commit now--and that | |
899 | ||
900 | ------------------------------------------------- | |
901 | $ git diff | |
902 | ------------------------------------------------- | |
903 | ||
904 | shows the difference between the working tree and the index file. | |
905 | ||
906 | Note that "git add" always adds just the current contents of a file | |
907 | to the index; further changes to the same file will be ignored unless | |
908 | you run git-add on the file again. | |
909 | ||
910 | When you're ready, just run | |
911 | ||
912 | ------------------------------------------------- | |
913 | $ git commit | |
914 | ------------------------------------------------- | |
915 | ||
916 | and git will prompt you for a commit message and then create the new | |
917 | commmit. Check to make sure it looks like what you expected with | |
918 | ||
919 | ------------------------------------------------- | |
920 | $ git show | |
921 | ------------------------------------------------- | |
922 | ||
923 | As a special shortcut, | |
924 | ||
925 | ------------------------------------------------- | |
926 | $ git commit -a | |
927 | ------------------------------------------------- | |
928 | ||
929 | will update the index with any files that you've modified or removed | |
930 | and create a commit, all in one step. | |
931 | ||
932 | A number of commands are useful for keeping track of what you're | |
933 | about to commit: | |
934 | ||
935 | ------------------------------------------------- | |
936 | $ git diff --cached # difference between HEAD and the index; what | |
937 | # would be commited if you ran "commit" now. | |
938 | $ git diff # difference between the index file and your | |
939 | # working directory; changes that would not | |
940 | # be included if you ran "commit" now. | |
941 | $ git status # a brief per-file summary of the above. | |
942 | ------------------------------------------------- | |
943 | ||
944 | creating good commit messages | |
945 | ----------------------------- | |
946 | ||
947 | Though not required, it's a good idea to begin the commit message | |
948 | with a single short (less than 50 character) line summarizing the | |
949 | change, followed by a blank line and then a more thorough | |
950 | description. Tools that turn commits into email, for example, use | |
951 | the first line on the Subject line and the rest of the commit in the | |
952 | body. | |
953 | ||
954 | how to merge | |
955 | ------------ | |
956 | ||
957 | You can rejoin two diverging branches of development using | |
958 | gitlink:git-merge[1]: | |
959 | ||
960 | ------------------------------------------------- | |
961 | $ git merge branchname | |
962 | ------------------------------------------------- | |
963 | ||
964 | merges the development in the branch "branchname" into the current | |
965 | branch. If there are conflicts--for example, if the same file is | |
966 | modified in two different ways in the remote branch and the local | |
967 | branch--then you are warned; the output may look something like this: | |
968 | ||
969 | ------------------------------------------------- | |
970 | $ git pull . next | |
971 | Trying really trivial in-index merge... | |
972 | fatal: Merge requires file-level merging | |
973 | Nope. | |
974 | Merging HEAD with 77976da35a11db4580b80ae27e8d65caf5208086 | |
975 | Merging: | |
976 | 15e2162 world | |
977 | 77976da goodbye | |
978 | found 1 common ancestor(s): | |
979 | d122ed4 initial | |
980 | Auto-merging file.txt | |
981 | CONFLICT (content): Merge conflict in file.txt | |
982 | Automatic merge failed; fix conflicts and then commit the result. | |
983 | ------------------------------------------------- | |
984 | ||
985 | Conflict markers are left in the problematic files, and after | |
986 | you resolve the conflicts manually, you can update the index | |
987 | with the contents and run git commit, as you normally would when | |
988 | creating a new file. | |
989 | ||
990 | If you examine the resulting commit using gitk, you will see that it | |
991 | has two parents, one pointing to the top of the current branch, and | |
992 | one to the top of the other branch. | |
993 | ||
994 | In more detail: | |
995 | ||
996 | [[resolving-a-merge]] | |
997 | Resolving a merge | |
998 | ----------------- | |
999 | ||
1000 | When a merge isn't resolved automatically, git leaves the index and | |
1001 | the working tree in a special state that gives you all the | |
1002 | information you need to help resolve the merge. | |
1003 | ||
1004 | Files with conflicts are marked specially in the index, so until you | |
1005 | resolve the problem and update the index, git commit will fail: | |
1006 | ||
1007 | ------------------------------------------------- | |
1008 | $ git commit | |
1009 | file.txt: needs merge | |
1010 | ------------------------------------------------- | |
1011 | ||
1012 | Also, git status will list those files as "unmerged". | |
1013 | ||
1014 | All of the changes that git was able to merge automatically are | |
1015 | already added to the index file, so gitlink:git-diff[1] shows only | |
1016 | the conflicts. Also, it uses a somewhat unusual syntax: | |
1017 | ||
1018 | ------------------------------------------------- | |
1019 | $ git diff | |
1020 | diff --cc file.txt | |
1021 | index 802992c,2b60207..0000000 | |
1022 | --- a/file.txt | |
1023 | +++ b/file.txt | |
1024 | @@@ -1,1 -1,1 +1,5 @@@ | |
1025 | ++<<<<<<< HEAD:file.txt | |
1026 | +Hello world | |
1027 | ++======= | |
1028 | + Goodbye | |
1029 | ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1030 | ------------------------------------------------- | |
1031 | ||
1032 | Recall that the commit which will be commited after we resolve this | |
1033 | conflict will have two parents instead of the usual one: one parent | |
1034 | will be HEAD, the tip of the current branch; the other will be the | |
1035 | tip of the other branch, which is stored temporarily in MERGE_HEAD. | |
1036 | ||
1037 | The diff above shows the differences between the working-tree version | |
1038 | of file.txt and two previous version: one version from HEAD, and one | |
1039 | from MERGE_HEAD. So instead of preceding each line by a single "+" | |
1040 | or "-", it now uses two columns: the first column is used for | |
1041 | differences between the first parent and the working directory copy, | |
1042 | and the second for differences between the second parent and the | |
1043 | working directory copy. Thus after resolving the conflict in the | |
1044 | obvious way, the diff will look like: | |
1045 | ||
1046 | ------------------------------------------------- | |
1047 | $ git diff | |
1048 | diff --cc file.txt | |
1049 | index 802992c,2b60207..0000000 | |
1050 | --- a/file.txt | |
1051 | +++ b/file.txt | |
1052 | @@@ -1,1 -1,1 +1,1 @@@ | |
1053 | - Hello world | |
1054 | -Goodbye | |
1055 | ++Goodbye world | |
1056 | ------------------------------------------------- | |
1057 | ||
1058 | This shows that our resolved version deleted "Hello world" from the | |
1059 | first parent, deleted "Goodbye" from the second parent, and added | |
1060 | "Goodbye world", which was previously absent from both. | |
1061 | ||
1062 | The gitlink:git-log[1] command also provides special help for merges: | |
1063 | ||
1064 | ------------------------------------------------- | |
1065 | $ git log --merge | |
1066 | ------------------------------------------------- | |
1067 | ||
1068 | This will list all commits which exist only on HEAD or on MERGE_HEAD, | |
1069 | and which touch an unmerged file. | |
1070 | ||
1071 | We can now add the resolved version to the index and commit: | |
1072 | ||
1073 | ------------------------------------------------- | |
1074 | $ git add file.txt | |
1075 | $ git commit | |
1076 | ------------------------------------------------- | |
1077 | ||
1078 | Note that the commit message will already be filled in for you with | |
1079 | some information about the merge. Normally you can just use this | |
1080 | default message unchanged, but you may add additional commentary of | |
1081 | your own if desired. | |
1082 | ||
1083 | [[undoing-a-merge]] | |
1084 | undoing a merge | |
1085 | --------------- | |
1086 | ||
1087 | If you get stuck and decide to just give up and throw the whole mess | |
1088 | away, you can always return to the pre-merge state with | |
1089 | ||
1090 | ------------------------------------------------- | |
1091 | $ git reset --hard HEAD | |
1092 | ------------------------------------------------- | |
1093 | ||
1094 | Or, if you've already commited the merge that you want to throw away, | |
1095 | ||
1096 | ------------------------------------------------- | |
1097 | $ git reset --hard HEAD^ | |
1098 | ------------------------------------------------- | |
1099 | ||
1100 | However, this last command can be dangerous in some cases--never | |
1101 | throw away a commit you have already committed if that commit may | |
1102 | itself have been merged into another branch, as doing so may confuse | |
1103 | further merges. | |
1104 | ||
1105 | Fast-forward merges | |
1106 | ------------------- | |
1107 | ||
1108 | There is one special case not mentioned above, which is treated | |
1109 | differently. Normally, a merge results in a merge commit, with two | |
1110 | parents, one pointing at each of the two lines of development that | |
1111 | were merged. | |
1112 | ||
1113 | However, if one of the two lines of development is completely | |
1114 | contained within the other--so every commit present in the one is | |
1115 | already contained in the other--then git just performs a | |
1116 | <<fast-forwards,fast forward>>; the head of the current branch is | |
1117 | moved forward to point at the head of the merged-in branch, without | |
1118 | any new commits being created. | |
1119 | ||
b684f830 BF |
1120 | Fixing mistakes |
1121 | --------------- | |
1122 | ||
1123 | If you've messed up the working tree, but haven't yet committed your | |
1124 | mistake, you can return the entire working tree to the last committed | |
1125 | state with | |
1126 | ||
1127 | ------------------------------------------------- | |
1128 | $ git reset --hard HEAD | |
1129 | ------------------------------------------------- | |
1130 | ||
1131 | If you make a commit that you later wish you hadn't, there are two | |
1132 | fundamentally different ways to fix the problem: | |
1133 | ||
1134 | 1. You can create a new commit that undoes whatever was done | |
1135 | by the previous commit. This is the correct thing if your | |
1136 | mistake has already been made public. | |
1137 | ||
1138 | 2. You can go back and modify the old commit. You should | |
1139 | never do this if you have already made the history public; | |
1140 | git does not normally expect the "history" of a project to | |
1141 | change, and cannot correctly perform repeated merges from | |
1142 | a branch that has had its history changed. | |
1143 | ||
1144 | Fixing a mistake with a new commit | |
1145 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1146 | ||
1147 | Creating a new commit that reverts an earlier change is very easy; | |
1148 | just pass the gitlink:git-revert[1] command a reference to the bad | |
1149 | commit; for example, to revert the most recent commit: | |
1150 | ||
1151 | ------------------------------------------------- | |
1152 | $ git revert HEAD | |
1153 | ------------------------------------------------- | |
1154 | ||
1155 | This will create a new commit which undoes the change in HEAD. You | |
1156 | will be given a chance to edit the commit message for the new commit. | |
1157 | ||
1158 | You can also revert an earlier change, for example, the next-to-last: | |
1159 | ||
1160 | ------------------------------------------------- | |
1161 | $ git revert HEAD^ | |
1162 | ------------------------------------------------- | |
1163 | ||
1164 | In this case git will attempt to undo the old change while leaving | |
1165 | intact any changes made since then. If more recent changes overlap | |
1166 | with the changes to be reverted, then you will be asked to fix | |
1167 | conflicts manually, just as in the case of <<resolving-a-merge, | |
1168 | resolving a merge>>. | |
1169 | ||
1170 | Fixing a mistake by editing history | |
1171 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1172 | ||
1173 | If the problematic commit is the most recent commit, and you have not | |
1174 | yet made that commit public, then you may just | |
1175 | <<undoing-a-merge,destroy it using git-reset>>. | |
1176 | ||
1177 | Alternatively, you | |
1178 | can edit the working directory and update the index to fix your | |
1179 | mistake, just as if you were going to <<how-to-make-a-commit,create a | |
1180 | new commit>>, then run | |
1181 | ||
1182 | ------------------------------------------------- | |
1183 | $ git commit --amend | |
1184 | ------------------------------------------------- | |
1185 | ||
1186 | which will replace the old commit by a new commit incorporating your | |
1187 | changes, giving you a chance to edit the old commit message first. | |
1188 | ||
1189 | Again, you should never do this to a commit that may already have | |
1190 | been merged into another branch; use gitlink:git-revert[1] instead in | |
1191 | that case. | |
1192 | ||
1193 | It is also possible to edit commits further back in the history, but | |
1194 | this is an advanced topic to be left for | |
1195 | <<cleaning-up-history,another chapter>>. | |
1196 | ||
1197 | Checking out an old version of a file | |
1198 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1199 | ||
1200 | In the process of undoing a previous bad change, you may find it | |
1201 | useful to check out an older version of a particular file using | |
1202 | gitlink:git-checkout[1]. We've used git checkout before to switch | |
1203 | branches, but it has quite different behavior if it is given a path | |
1204 | name: the command | |
1205 | ||
1206 | ------------------------------------------------- | |
1207 | $ git checkout HEAD^ path/to/file | |
1208 | ------------------------------------------------- | |
1209 | ||
1210 | replaces path/to/file by the contents it had in the commit HEAD^, and | |
1211 | also updates the index to match. It does not change branches. | |
1212 | ||
1213 | If you just want to look at an old version of the file, without | |
1214 | modifying the working directory, you can do that with | |
1215 | gitlink:git-show[1]: | |
1216 | ||
1217 | ------------------------------------------------- | |
1218 | $ git show HEAD^ path/to/file | |
1219 | ------------------------------------------------- | |
1220 | ||
1221 | which will display the given version of the file. | |
1222 | ||
d19fbc3c BF |
1223 | Ensuring good performance |
1224 | ------------------------- | |
1225 | ||
1226 | On large repositories, git depends on compression to keep the history | |
1227 | information from taking up to much space on disk or in memory. | |
1228 | ||
1229 | This compression is not performed automatically. Therefore you | |
1230 | should occasionally run | |
1231 | ||
1232 | ------------------------------------------------- | |
1233 | $ git gc | |
1234 | ------------------------------------------------- | |
1235 | ||
1236 | to recompress the archive and to prune any commits which are no | |
1237 | longer referred to anywhere. This can be very time-consuming, and | |
1238 | you should not modify the repository while it is working, so you | |
1239 | should run it while you are not working. | |
1240 | ||
1241 | Sharing development with others | |
b684f830 | 1242 | =============================== |
d19fbc3c BF |
1243 | |
1244 | [[getting-updates-with-git-pull]] | |
1245 | Getting updates with git pull | |
b684f830 | 1246 | ----------------------------- |
d19fbc3c BF |
1247 | |
1248 | After you clone a repository and make a few changes of your own, you | |
1249 | may wish to check the original repository for updates and merge them | |
1250 | into your own work. | |
1251 | ||
1252 | We have already seen <<Updating-a-repository-with-git-fetch,how to | |
1253 | keep remote tracking branches up to date>> with gitlink:git-fetch[1], | |
1254 | and how to merge two branches. So you can merge in changes from the | |
1255 | original repository's master branch with: | |
1256 | ||
1257 | ------------------------------------------------- | |
1258 | $ git fetch | |
1259 | $ git merge origin/master | |
1260 | ------------------------------------------------- | |
1261 | ||
1262 | However, the gitlink:git-pull[1] command provides a way to do this in | |
1263 | one step: | |
1264 | ||
1265 | ------------------------------------------------- | |
1266 | $ git pull origin master | |
1267 | ------------------------------------------------- | |
1268 | ||
1269 | In fact, "origin" is normally the default repository to pull from, | |
1270 | and the default branch is normally the HEAD of the remote repository, | |
1271 | so often you can accomplish the above with just | |
1272 | ||
1273 | ------------------------------------------------- | |
1274 | $ git pull | |
1275 | ------------------------------------------------- | |
1276 | ||
1277 | See the descriptions of the branch.<name>.remote and | |
1278 | branch.<name>.merge options in gitlink:git-repo-config[1] to learn | |
1279 | how to control these defaults depending on the current branch. | |
1280 | ||
1281 | In addition to saving you keystrokes, "git pull" also helps you by | |
1282 | producing a default commit message documenting the branch and | |
1283 | repository that you pulled from. | |
1284 | ||
1285 | (But note that no such commit will be created in the case of a | |
1286 | <<fast-forwards,fast forward>>; instead, your branch will just be | |
1287 | updated to point to the latest commit from the upstream branch). | |
1288 | ||
4c63ff45 BF |
1289 | The git-pull command can also be given "." as the "remote" repository, in |
1290 | which case it just merges in a branch from the current repository; so | |
1291 | the commands | |
1292 | ||
1293 | ------------------------------------------------- | |
1294 | $ git pull . branch | |
1295 | $ git merge branch | |
1296 | ------------------------------------------------- | |
1297 | ||
1298 | are roughly equivalent. The former is actually very commonly used. | |
1299 | ||
d19fbc3c | 1300 | Submitting patches to a project |
b684f830 | 1301 | ------------------------------- |
d19fbc3c BF |
1302 | |
1303 | If you just have a few changes, the simplest way to submit them may | |
1304 | just be to send them as patches in email: | |
1305 | ||
1306 | First, use gitlink:git-format-patches[1]; for example: | |
1307 | ||
1308 | ------------------------------------------------- | |
eb6ae7f4 | 1309 | $ git format-patch origin |
d19fbc3c BF |
1310 | ------------------------------------------------- |
1311 | ||
1312 | will produce a numbered series of files in the current directory, one | |
1313 | for each patch in the current branch but not in origin/HEAD. | |
1314 | ||
1315 | You can then import these into your mail client and send them by | |
1316 | hand. However, if you have a lot to send at once, you may prefer to | |
1317 | use the gitlink:git-send-email[1] script to automate the process. | |
1318 | Consult the mailing list for your project first to determine how they | |
1319 | prefer such patches be handled. | |
1320 | ||
1321 | Importing patches to a project | |
b684f830 | 1322 | ------------------------------ |
d19fbc3c BF |
1323 | |
1324 | Git also provides a tool called gitlink:git-am[1] (am stands for | |
1325 | "apply mailbox"), for importing such an emailed series of patches. | |
1326 | Just save all of the patch-containing messages, in order, into a | |
1327 | single mailbox file, say "patches.mbox", then run | |
1328 | ||
1329 | ------------------------------------------------- | |
eb6ae7f4 | 1330 | $ git am -3 patches.mbox |
d19fbc3c BF |
1331 | ------------------------------------------------- |
1332 | ||
1333 | Git will apply each patch in order; if any conflicts are found, it | |
1334 | will stop, and you can fix the conflicts as described in | |
01997b4a BF |
1335 | "<<resolving-a-merge,Resolving a merge>>". (The "-3" option tells |
1336 | git to perform a merge; if you would prefer it just to abort and | |
1337 | leave your tree and index untouched, you may omit that option.) | |
1338 | ||
1339 | Once the index is updated with the results of the conflict | |
1340 | resolution, instead of creating a new commit, just run | |
d19fbc3c BF |
1341 | |
1342 | ------------------------------------------------- | |
1343 | $ git am --resolved | |
1344 | ------------------------------------------------- | |
1345 | ||
1346 | and git will create the commit for you and continue applying the | |
1347 | remaining patches from the mailbox. | |
1348 | ||
1349 | The final result will be a series of commits, one for each patch in | |
1350 | the original mailbox, with authorship and commit log message each | |
1351 | taken from the message containing each patch. | |
1352 | ||
1353 | [[setting-up-a-public-repository]] | |
1354 | Setting up a public repository | |
b684f830 | 1355 | ------------------------------ |
d19fbc3c BF |
1356 | |
1357 | Another way to submit changes to a project is to simply tell the | |
1358 | maintainer of that project to pull from your repository, exactly as | |
1359 | you did in the section "<<getting-updates-with-git-pull, Getting | |
1360 | updates with git pull>>". | |
1361 | ||
1362 | If you and maintainer both have accounts on the same machine, then | |
1363 | then you can just pull changes from each other's repositories | |
1364 | directly; note that all of the command (gitlink:git-clone[1], | |
1365 | git-fetch[1], git-pull[1], etc.) which accept a URL as an argument | |
1366 | will also accept a local file patch; so, for example, you can | |
1367 | use | |
1368 | ||
1369 | ------------------------------------------------- | |
1370 | $ git clone /path/to/repository | |
1371 | $ git pull /path/to/other/repository | |
1372 | ------------------------------------------------- | |
1373 | ||
1374 | If this sort of setup is inconvenient or impossible, another (more | |
1375 | common) option is to set up a public repository on a public server. | |
1376 | This also allows you to cleanly separate private work in progress | |
1377 | from publicly visible work. | |
1378 | ||
1379 | You will continue to do your day-to-day work in your personal | |
1380 | repository, but periodically "push" changes from your personal | |
1381 | repository into your public repository, allowing other developers to | |
1382 | pull from that repository. So the flow of changes, in a situation | |
1383 | where there is one other developer with a public repository, looks | |
1384 | like this: | |
1385 | ||
1386 | you push | |
1387 | your personal repo ------------------> your public repo | |
1388 | ^ | | |
1389 | | | | |
1390 | | you pull | they pull | |
1391 | | | | |
1392 | | | | |
1393 | | they push V | |
1394 | their public repo <------------------- their repo | |
1395 | ||
1396 | Now, assume your personal repository is in the directory ~/proj. We | |
1397 | first create a new clone of the repository: | |
1398 | ||
1399 | ------------------------------------------------- | |
1400 | $ git clone --bare proj-clone.git | |
1401 | ------------------------------------------------- | |
1402 | ||
1403 | The resulting directory proj-clone.git will contains a "bare" git | |
1404 | repository--it is just the contents of the ".git" directory, without | |
1405 | a checked-out copy of a working directory. | |
1406 | ||
1407 | Next, copy proj-clone.git to the server where you plan to host the | |
1408 | public repository. You can use scp, rsync, or whatever is most | |
1409 | convenient. | |
1410 | ||
1411 | If somebody else maintains the public server, they may already have | |
1412 | set up a git service for you, and you may skip to the section | |
1413 | "<<pushing-changes-to-a-public-repository,Pushing changes to a public | |
1414 | repository>>", below. | |
1415 | ||
1416 | Otherwise, the following sections explain how to export your newly | |
1417 | created public repository: | |
1418 | ||
1419 | [[exporting-via-http]] | |
1420 | Exporting a git repository via http | |
b684f830 | 1421 | ----------------------------------- |
d19fbc3c BF |
1422 | |
1423 | The git protocol gives better performance and reliability, but on a | |
1424 | host with a web server set up, http exports may be simpler to set up. | |
1425 | ||
1426 | All you need to do is place the newly created bare git repository in | |
1427 | a directory that is exported by the web server, and make some | |
1428 | adjustments to give web clients some extra information they need: | |
1429 | ||
1430 | ------------------------------------------------- | |
1431 | $ mv proj.git /home/you/public_html/proj.git | |
1432 | $ cd proj.git | |
1433 | $ git update-server-info | |
1434 | $ chmod a+x hooks/post-update | |
1435 | ------------------------------------------------- | |
1436 | ||
1437 | (For an explanation of the last two lines, see | |
1438 | gitlink:git-update-server-info[1], and the documentation | |
1439 | link:hooks.txt[Hooks used by git].) | |
1440 | ||
1441 | Advertise the url of proj.git. Anybody else should then be able to | |
1442 | clone or pull from that url, for example with a commandline like: | |
1443 | ||
1444 | ------------------------------------------------- | |
1445 | $ git clone http://yourserver.com/~you/proj.git | |
1446 | ------------------------------------------------- | |
1447 | ||
1448 | (See also | |
1449 | link:howto/setup-git-server-over-http.txt[setup-git-server-over-http] | |
1450 | for a slightly more sophisticated setup using WebDAV which also | |
1451 | allows pushing over http.) | |
1452 | ||
1453 | [[exporting-via-git]] | |
1454 | Exporting a git repository via the git protocol | |
b684f830 | 1455 | ----------------------------------------------- |
d19fbc3c BF |
1456 | |
1457 | This is the preferred method. | |
1458 | ||
1459 | For now, we refer you to the gitlink:git-daemon[1] man page for | |
1460 | instructions. (See especially the examples section.) | |
1461 | ||
1462 | [[pushing-changes-to-a-public-repository]] | |
1463 | Pushing changes to a public repository | |
b684f830 | 1464 | -------------------------------------- |
d19fbc3c BF |
1465 | |
1466 | Note that the two techniques outline above (exporting via | |
1467 | <<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other | |
1468 | maintainers to fetch your latest changes, but they do not allow write | |
1469 | access, which you will need to update the public repository with the | |
1470 | latest changes created in your private repository. | |
1471 | ||
1472 | The simplest way to do this is using gitlink:git-push[1] and ssh; to | |
1473 | update the remote branch named "master" with the latest state of your | |
1474 | branch named "master", run | |
1475 | ||
1476 | ------------------------------------------------- | |
1477 | $ git push ssh://yourserver.com/~you/proj.git master:master | |
1478 | ------------------------------------------------- | |
1479 | ||
1480 | or just | |
1481 | ||
1482 | ------------------------------------------------- | |
1483 | $ git push ssh://yourserver.com/~you/proj.git master | |
1484 | ------------------------------------------------- | |
1485 | ||
1486 | As with git-fetch, git-push will complain if this does not result in | |
1487 | a <<fast-forwards,fast forward>>. Normally this is a sign of | |
1488 | something wrong. However, if you are sure you know what you're | |
1489 | doing, you may force git-push to perform the update anyway by | |
1490 | proceeding the branch name by a plus sign: | |
1491 | ||
1492 | ------------------------------------------------- | |
1493 | $ git push ssh://yourserver.com/~you/proj.git +master | |
1494 | ------------------------------------------------- | |
1495 | ||
1496 | As with git-fetch, you may also set up configuration options to | |
1497 | save typing; so, for example, after | |
1498 | ||
1499 | ------------------------------------------------- | |
1500 | $ cat >.git/config <<EOF | |
1501 | [remote "public-repo"] | |
1502 | url = ssh://yourserver.com/~you/proj.git | |
1503 | EOF | |
1504 | ------------------------------------------------- | |
1505 | ||
1506 | you should be able to perform the above push with just | |
1507 | ||
1508 | ------------------------------------------------- | |
1509 | $ git push public-repo master | |
1510 | ------------------------------------------------- | |
1511 | ||
1512 | See the explanations of the remote.<name>.url, branch.<name>.remote, | |
1513 | and remote.<name>.push options in gitlink:git-repo-config[1] for | |
1514 | details. | |
1515 | ||
1516 | Setting up a shared repository | |
b684f830 | 1517 | ------------------------------ |
d19fbc3c BF |
1518 | |
1519 | Another way to collaborate is by using a model similar to that | |
1520 | commonly used in CVS, where several developers with special rights | |
1521 | all push to and pull from a single shared repository. See | |
1522 | link:cvs-migration.txt[git for CVS users] for instructions on how to | |
1523 | set this up. | |
1524 | ||
b684f830 BF |
1525 | Allow web browsing of a repository |
1526 | ---------------------------------- | |
d19fbc3c | 1527 | |
b684f830 | 1528 | TODO: Brief setup-instructions for gitweb |
d19fbc3c | 1529 | |
b684f830 BF |
1530 | Examples |
1531 | -------- | |
d19fbc3c | 1532 | |
b684f830 | 1533 | TODO: topic branches, typical roles as in everyday.txt, ? |
d19fbc3c | 1534 | |
d19fbc3c BF |
1535 | |
1536 | Working with other version control systems | |
1537 | ========================================== | |
1538 | ||
4c63ff45 | 1539 | TODO: CVS, Subversion, series-of-release-tarballs, ? |
d19fbc3c BF |
1540 | |
1541 | [[cleaning-up-history]] | |
4c63ff45 BF |
1542 | Rewriting history and maintaining patch series |
1543 | ============================================== | |
1544 | ||
1545 | Normally commits are only added to a project, never taken away or | |
1546 | replaced. Git is designed with this assumption, and violating it will | |
1547 | cause git's merge machinery (for example) to do the wrong thing. | |
1548 | ||
1549 | However, there is a situation in which it can be useful to violate this | |
1550 | assumption. | |
1551 | ||
1552 | Creating the perfect patch series | |
1553 | --------------------------------- | |
1554 | ||
1555 | Suppose you are a contributor to a large project, and you want to add a | |
1556 | complicated feature, and to present it to the other developers in a way | |
1557 | that makes it easy for them to read your changes, verify that they are | |
1558 | correct, and understand why you made each change. | |
1559 | ||
1560 | If you present all of your changes as a single patch (or commit), they may | |
1561 | find it is too much to digest all at once. | |
1562 | ||
1563 | If you present them with the entire history of your work, complete with | |
1564 | mistakes, corrections, and dead ends, they may be overwhelmed. | |
1565 | ||
1566 | So the ideal is usually to produce a series of patches such that: | |
1567 | ||
1568 | 1. Each patch can be applied in order. | |
1569 | ||
1570 | 2. Each patch includes a single logical change, together with a | |
1571 | message explaining the change. | |
1572 | ||
1573 | 3. No patch introduces a regression: after applying any initial | |
1574 | part of the series, the resulting project still compiles and | |
1575 | works, and has no bugs that it didn't have before. | |
1576 | ||
1577 | 4. The complete series produces the same end result as your own | |
1578 | (probably much messier!) development process did. | |
1579 | ||
1580 | We will introduce some tools that can help you do this, explain how to use | |
1581 | them, and then explain some of the problems that can arise because you are | |
1582 | rewriting history. | |
1583 | ||
1584 | Keeping a patch series up to date using git-rebase | |
1585 | -------------------------------------------------- | |
1586 | ||
1587 | Suppose you have a series of commits in a branch "mywork", which | |
1588 | originally branched off from "origin". | |
1589 | ||
1590 | Suppose you create a branch "mywork" on a remote-tracking branch "origin", | |
1591 | and created some commits on top of it: | |
1592 | ||
1593 | ------------------------------------------------- | |
1594 | $ git checkout -b mywork origin | |
1595 | $ vi file.txt | |
1596 | $ git commit | |
1597 | $ vi otherfile.txt | |
1598 | $ git commit | |
1599 | ... | |
1600 | ------------------------------------------------- | |
1601 | ||
1602 | You have performed no merges into mywork, so it is just a simple linear | |
1603 | sequence of patches on top of "origin": | |
1604 | ||
1605 | ||
1606 | o--o--o <-- origin | |
1607 | \ | |
1608 | o--o--o <-- mywork | |
1609 | ||
1610 | Some more interesting work has been done in the upstream project, and | |
1611 | "origin" has advanced: | |
1612 | ||
1613 | o--o--O--o--o--o <-- origin | |
1614 | \ | |
1615 | a--b--c <-- mywork | |
1616 | ||
1617 | At this point, you could use "pull" to merge your changes back in; | |
1618 | the result would create a new merge commit, like this: | |
1619 | ||
1620 | ||
1621 | o--o--O--o--o--o <-- origin | |
1622 | \ \ | |
1623 | a--b--c--m <-- mywork | |
1624 | ||
1625 | However, if you prefer to keep the history in mywork a simple series of | |
1626 | commits without any merges, you may instead choose to use | |
1627 | gitlink:git-rebase[1]: | |
1628 | ||
1629 | ------------------------------------------------- | |
1630 | $ git checkout mywork | |
1631 | $ git rebase origin | |
1632 | ------------------------------------------------- | |
1633 | ||
1634 | This will remove each of your commits from mywork, temporarily saving them | |
1635 | as patches (in a directory named ".dotest"), update mywork to point at the | |
1636 | latest version of origin, then apply each of the saved patches to the new | |
1637 | mywork. The result will look like: | |
1638 | ||
1639 | ||
1640 | o--o--O--o--o--o <-- origin | |
1641 | \ | |
1642 | a'--b'--c' <-- mywork | |
1643 | ||
1644 | In the process, it may discover conflicts. In that case it will stop and | |
1645 | allow you to fix the conflicts as described in | |
aec053bb BF |
1646 | "<<resolving-a-merge,Resolving a merge>>". |
1647 | ||
1648 | XXX: no, maybe not: git diff doesn't produce very useful results, and there's | |
1649 | no MERGE_HEAD. | |
1650 | ||
1651 | Once the index is updated with | |
4c63ff45 BF |
1652 | the results of the conflict resolution, instead of creating a new commit, |
1653 | just run | |
1654 | ||
1655 | ------------------------------------------------- | |
1656 | $ git rebase --continue | |
1657 | ------------------------------------------------- | |
1658 | ||
1659 | and git will continue applying the rest of the patches. | |
1660 | ||
1661 | At any point you may use the --abort option to abort this process and | |
1662 | return mywork to the state it had before you started the rebase: | |
1663 | ||
1664 | ------------------------------------------------- | |
1665 | $ git rebase --abort | |
1666 | ------------------------------------------------- | |
1667 | ||
1668 | Reordering or selecting from a patch series | |
1669 | ------------------------------------------- | |
1670 | ||
1671 | Given one existing commit, the gitlink:git-cherry-pick[1] command allows | |
1672 | you to apply the change introduced by that commit and create a new commit | |
1673 | that records it. | |
1674 | ||
1675 | This can be useful for modifying a patch series. | |
1676 | ||
1677 | TODO: elaborate | |
1678 | ||
1679 | Other tools | |
1680 | ----------- | |
1681 | ||
1682 | There are numerous other tools, such as stgit, which exist for the purpose | |
1683 | of maintianing a patch series. These are out of the scope of this manual. | |
1684 | ||
1685 | Problems with rewriting history | |
1686 | ------------------------------- | |
1687 | ||
1688 | The primary problem with rewriting the history of a branch has to do with | |
1689 | merging. | |
1690 | ||
1691 | TODO: elaborate | |
d19fbc3c | 1692 | |
d19fbc3c BF |
1693 | |
1694 | Git internals | |
1695 | ============= | |
1696 | ||
1697 | Architectural overview | |
1698 | ---------------------- | |
1699 | ||
1700 | TODO: Sources, README, core-tutorial, tutorial-2.txt, technical/ | |
1701 | ||
1702 | Glossary of git terms | |
1703 | ===================== | |
1704 | ||
1705 | include::glossary.txt[] | |
1706 | ||
6bd9b682 BF |
1707 | Notes and todo list for this manual |
1708 | =================================== | |
1709 | ||
1710 | This is a work in progress. | |
1711 | ||
1712 | The basic requirements: | |
1713 | - It must be readable in order, from beginning to end, by someone | |
1714 | intelligent with a basic grasp of the unix commandline, but | |
1715 | without any special knowledge of git. If necessary, any other | |
1716 | prerequisites should be specifically mentioned as they arise. | |
1717 | - Whenever possible, section headings should clearly describe the | |
1718 | task they explain how to do, in language that requires no more | |
1719 | knowledge than necessary: for example, "importing patches into a | |
1720 | project" rather than "the git-am command" | |
1721 | ||
d5cd5de4 BF |
1722 | Think about how to create a clear chapter dependency graph that will |
1723 | allow people to get to important topics without necessarily reading | |
1724 | everything in between. | |
d19fbc3c BF |
1725 | |
1726 | Scan Documentation/ for other stuff left out; in particular: | |
1727 | howto's | |
1728 | README | |
1729 | some of technical/? | |
1730 | hooks | |
1731 | etc. | |
1732 | ||
1733 | Scan email archives for other stuff left out | |
1734 | ||
1735 | Scan man pages to see if any assume more background than this manual | |
1736 | provides. | |
1737 | ||
d5cd5de4 BF |
1738 | Simplify beginning by suggesting disconnected head instead of temporary |
1739 | branch creation. | |
d19fbc3c BF |
1740 | |
1741 | Explain how to refer to file stages in the "how to resolve a merge" | |
e9c0390a BF |
1742 | section: diff -1, -2, -3, --ours, --theirs :1:/path notation. The |
1743 | "git ls-files --unmerged --stage" thing is sorta useful too, actually. And | |
1744 | note gitk --merge. Also what's easiest way to see common merge base? | |
1745 | ||
b684f830 BF |
1746 | Add more good examples. Entire sections of just cookbook examples might |
1747 | be a good idea; maybe make an "advanced examples" section a standard | |
1748 | end-of-chapter section? | |
d19fbc3c BF |
1749 | |
1750 | Include cross-references to the glossary, where appropriate. | |
1751 | ||
e9c0390a BF |
1752 | To document: |
1753 | reflogs, git reflog expire | |
1754 | shallow clones?? See draft 1.5.0 release notes for some documentation. |