Correct ordering in git-cvsimport's option documentation
[git/git.git] / Documentation / user-manual.txt
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1Git User's Manual
2_________________
3
4This manual is designed to be readable by someone with basic unix
5commandline skills, but no previous knowledge of git.
6
ef89f701 7Chapter 1 gives a brief overview of git commands, without any
b181d57f 8explanation; you may prefer to skip to chapter 2 on a first reading.
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9
10Chapters 2 and 3 explain how to fetch and study a project using
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11git--the tools you'd need to build and test a particular version of a
12software project, to search for regressions, and so on.
6bd9b682 13
ef89f701 14Chapter 4 explains how to do development with git, and chapter 5 how
d5cd5de4 15to share that development with others.
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16
17Further chapters cover more specialized topics.
18
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19Comprehensive reference documentation is available through the man
20pages. For a command such as "git clone", just use
21
22------------------------------------------------
23$ man git-clone
24------------------------------------------------
25
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26Git Quick Start
27===============
28
29This is a quick summary of the major commands; the following chapters
30will explain how these work in more detail.
31
32Creating a new repository
33-------------------------
34
35From a tarball:
36
37-----------------------------------------------
38$ tar xzf project.tar.gz
39$ cd project
40$ git init
41Initialized empty Git repository in .git/
42$ git add .
43$ git commit
44-----------------------------------------------
45
46From a remote repository:
47
48-----------------------------------------------
49$ git clone git://example.com/pub/project.git
50$ cd project
51-----------------------------------------------
52
53Managing branches
54-----------------
55
56-----------------------------------------------
57$ git branch # list all branches in this repo
58$ git checkout test # switch working directory to branch "test"
59$ git branch new # create branch "new" starting at current HEAD
60$ git branch -d new # delete branch "new"
61-----------------------------------------------
62
63Instead of basing new branch on current HEAD (the default), use:
64
65-----------------------------------------------
66$ git branch new test # branch named "test"
67$ git branch new v2.6.15 # tag named v2.6.15
68$ git branch new HEAD^ # commit before the most recent
69$ git branch new HEAD^^ # commit before that
70$ git branch new test~10 # ten commits before tip of branch "test"
71-----------------------------------------------
72
73Create and switch to a new branch at the same time:
74
75-----------------------------------------------
76$ git checkout -b new v2.6.15
77-----------------------------------------------
78
79Update and examine branches from the repository you cloned from:
80
81-----------------------------------------------
82$ git fetch # update
83$ git branch -r # list
84 origin/master
85 origin/next
86 ...
87$ git branch checkout -b masterwork origin/master
88-----------------------------------------------
89
90Fetch a branch from a different repository, and give it a new
91name in your repository:
92
93-----------------------------------------------
94$ git fetch git://example.com/project.git theirbranch:mybranch
95$ git fetch git://example.com/project.git v2.6.15:mybranch
96-----------------------------------------------
97
98Keep a list of repositories you work with regularly:
99
100-----------------------------------------------
101$ git remote add example git://example.com/project.git
b181d57f 102$ git remote # list remote repositories
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103example
104origin
b181d57f 105$ git remote show example # get details
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106* remote example
107 URL: git://example.com/project.git
108 Tracked remote branches
109 master next ...
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110$ git fetch example # update branches from example
111$ git branch -r # list all remote branches
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112-----------------------------------------------
113
114
115Exploring history
116-----------------
117
118-----------------------------------------------
119$ gitk # visualize and browse history
120$ git log # list all commits
121$ git log src/ # ...modifying src/
122$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
123$ git log master..test # ...in branch test, not in branch master
124$ git log test..master # ...in branch master, but not in test
125$ git log test...master # ...in one branch, not in both
126$ git log -S'foo()' # ...where difference contain "foo()"
127$ git log --since="2 weeks ago"
128$ git log -p # show patches as well
129$ git show # most recent commit
130$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
131$ git diff v2.6.15..HEAD # diff with current head
132$ git grep "foo()" # search working directory for "foo()"
133$ git grep v2.6.15 "foo()" # search old tree for "foo()"
134$ git show v2.6.15:a.txt # look at old version of a.txt
135-----------------------------------------------
136
b181d57f 137Search for regressions:
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138
139-----------------------------------------------
140$ git bisect start
141$ git bisect bad # current version is bad
142$ git bisect good v2.6.13-rc2 # last known good revision
143Bisecting: 675 revisions left to test after this
144 # test here, then:
145$ git bisect good # if this revision is good, or
146$ git bisect bad # if this revision is bad.
147 # repeat until done.
148-----------------------------------------------
149
150Making changes
151--------------
152
153Make sure git knows who to blame:
154
155------------------------------------------------
156$ cat >~/.gitconfig <<\EOF
157[user]
158name = Your Name Comes Here
159email = you@yourdomain.example.com
160EOF
161------------------------------------------------
162
163Select file contents to include in the next commit, then make the
164commit:
165
166-----------------------------------------------
167$ git add a.txt # updated file
168$ git add b.txt # new file
169$ git rm c.txt # old file
170$ git commit
171-----------------------------------------------
172
173Or, prepare and create the commit in one step:
174
175-----------------------------------------------
b181d57f 176$ git commit d.txt # use latest content only of d.txt
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177$ git commit -a # use latest content of all tracked files
178-----------------------------------------------
179
180Merging
181-------
182
183-----------------------------------------------
184$ git merge test # merge branch "test" into the current branch
185$ git pull git://example.com/project.git master
186 # fetch and merge in remote branch
187$ git pull . test # equivalent to git merge test
188-----------------------------------------------
189
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190Sharing your changes
191--------------------
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192
193Importing or exporting patches:
194
195-----------------------------------------------
196$ git format-patch origin..HEAD # format a patch for each commit
197 # in HEAD but not in origin
198$ git-am mbox # import patches from the mailbox "mbox"
199-----------------------------------------------
200
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201Fetch a branch in a different git repository, then merge into the
202current branch:
203
204-----------------------------------------------
205$ git pull git://example.com/project.git theirbranch
206-----------------------------------------------
207
208Store the fetched branch into a local branch before merging into the
209current branch:
210
211-----------------------------------------------
212$ git pull git://example.com/project.git theirbranch:mybranch
213-----------------------------------------------
214
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215After creating commits on a local branch, update the remote
216branch with your commits:
217
218-----------------------------------------------
219$ git push ssh://example.com/project.git mybranch:theirbranch
220-----------------------------------------------
221
222When remote and local branch are both named "test":
223
224-----------------------------------------------
225$ git push ssh://example.com/project.git test
226-----------------------------------------------
227
228Shortcut version for a frequently used remote repository:
229
230-----------------------------------------------
231$ git remote add example ssh://example.com/project.git
232$ git push example test
233-----------------------------------------------
234
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235Repository maintenance
236----------------------
237
238Check for corruption:
239
240-----------------------------------------------
04e50e94 241$ git fsck
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242-----------------------------------------------
243
244Recompress, remove unused cruft:
245
246-----------------------------------------------
247$ git gc
248-----------------------------------------------
249
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250Repositories and Branches
251=========================
252
253How to get a git repository
254---------------------------
255
256It will be useful to have a git repository to experiment with as you
257read this manual.
258
259The best way to get one is by using the gitlink:git-clone[1] command
260to download a copy of an existing repository for a project that you
261are interested in. If you don't already have a project in mind, here
262are some interesting examples:
263
264------------------------------------------------
265 # git itself (approx. 10MB download):
266$ git clone git://git.kernel.org/pub/scm/git/git.git
267 # the linux kernel (approx. 150MB download):
268$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
269------------------------------------------------
270
271The initial clone may be time-consuming for a large project, but you
272will only need to clone once.
273
274The clone command creates a new directory named after the project
275("git" or "linux-2.6" in the examples above). After you cd into this
276directory, you will see that it contains a copy of the project files,
277together with a special top-level directory named ".git", which
278contains all the information about the history of the project.
279
d5cd5de4 280In most of the following, examples will be taken from one of the two
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281repositories above.
282
283How to check out a different version of a project
284-------------------------------------------------
285
286Git is best thought of as a tool for storing the history of a
287collection of files. It stores the history as a compressed
288collection of interrelated snapshots (versions) of the project's
289contents.
290
291A single git repository may contain multiple branches. Each branch
292is a bookmark referencing a particular point in the project history.
293The gitlink:git-branch[1] command shows you the list of branches:
294
295------------------------------------------------
296$ git branch
297* master
298------------------------------------------------
299
300A freshly cloned repository contains a single branch, named "master",
301and the working directory contains the version of the project
302referred to by the master branch.
303
304Most projects also use tags. Tags, like branches, are references
305into the project's history, and can be listed using the
306gitlink:git-tag[1] command:
307
308------------------------------------------------
309$ git tag -l
310v2.6.11
311v2.6.11-tree
312v2.6.12
313v2.6.12-rc2
314v2.6.12-rc3
315v2.6.12-rc4
316v2.6.12-rc5
317v2.6.12-rc6
318v2.6.13
319...
320------------------------------------------------
321
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322Tags are expected to always point at the same version of a project,
323while branches are expected to advance as development progresses.
324
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325Create a new branch pointing to one of these versions and check it
326out using gitlink:git-checkout[1]:
327
328------------------------------------------------
329$ git checkout -b new v2.6.13
330------------------------------------------------
331
332The working directory then reflects the contents that the project had
333when it was tagged v2.6.13, and gitlink:git-branch[1] shows two
334branches, with an asterisk marking the currently checked-out branch:
335
336------------------------------------------------
337$ git branch
338 master
339* new
340------------------------------------------------
341
342If you decide that you'd rather see version 2.6.17, you can modify
343the current branch to point at v2.6.17 instead, with
344
345------------------------------------------------
346$ git reset --hard v2.6.17
347------------------------------------------------
348
349Note that if the current branch was your only reference to a
350particular point in history, then resetting that branch may leave you
351with no way to find the history it used to point to; so use this
352command carefully.
353
354Understanding History: Commits
355------------------------------
356
357Every change in the history of a project is represented by a commit.
358The gitlink:git-show[1] command shows the most recent commit on the
359current branch:
360
361------------------------------------------------
362$ git show
363commit 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2
364Author: Jamal Hadi Salim <hadi@cyberus.ca>
365Date: Sat Dec 2 22:22:25 2006 -0800
366
367 [XFRM]: Fix aevent structuring to be more complete.
368
369 aevents can not uniquely identify an SA. We break the ABI with this
370 patch, but consensus is that since it is not yet utilized by any
371 (known) application then it is fine (better do it now than later).
372
373 Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
374 Signed-off-by: David S. Miller <davem@davemloft.net>
375
376diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt
377index 8be626f..d7aac9d 100644
378--- a/Documentation/networking/xfrm_sync.txt
379+++ b/Documentation/networking/xfrm_sync.txt
380@@ -47,10 +47,13 @@ aevent_id structure looks like:
381
382 struct xfrm_aevent_id {
383 struct xfrm_usersa_id sa_id;
384+ xfrm_address_t saddr;
385 __u32 flags;
386+ __u32 reqid;
387 };
388...
389------------------------------------------------
390
391As you can see, a commit shows who made the latest change, what they
392did, and why.
393
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394Every commit has a 40-hexdigit id, sometimes called the "object name"
395or the "SHA1 id", shown on the first line of the "git show" output.
396You can usually refer to a commit by a shorter name, such as a tag or a
397branch name, but this longer name can also be useful. Most
398importantly, it is a globally unique name for this commit: so if you
399tell somebody else the object name (for example in email), then you are
400guaranteed that name will refer to the same commit in their repository
aacd404e 401that it does in yours (assuming their repository has that commit at
b181d57f 402all).
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403
404Understanding history: commits, parents, and reachability
405~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
406
407Every commit (except the very first commit in a project) also has a
408parent commit which shows what happened before this commit.
409Following the chain of parents will eventually take you back to the
410beginning of the project.
411
412However, the commits do not form a simple list; git allows lines of
413development to diverge and then reconverge, and the point where two
414lines of development reconverge is called a "merge". The commit
415representing a merge can therefore have more than one parent, with
416each parent representing the most recent commit on one of the lines
417of development leading to that point.
418
419The best way to see how this works is using the gitlink:gitk[1]
420command; running gitk now on a git repository and looking for merge
421commits will help understand how the git organizes history.
422
423In the following, we say that commit X is "reachable" from commit Y
424if commit X is an ancestor of commit Y. Equivalently, you could say
425that Y is a descendent of X, or that there is a chain of parents
426leading from commit Y to commit X.
427
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428Understanding history: History diagrams
429~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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430
431We will sometimes represent git history using diagrams like the one
432below. Commits are shown as "o", and the links between them with
433lines drawn with - / and \. Time goes left to right:
434
435 o--o--o <-- Branch A
436 /
437 o--o--o <-- master
438 \
439 o--o--o <-- Branch B
440
441If we need to talk about a particular commit, the character "o" may
442be replaced with another letter or number.
443
444Understanding history: What is a branch?
445~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
446
447Though we've been using the word "branch" to mean a kind of reference
448to a particular commit, the word branch is also commonly used to
449refer to the line of commits leading up to that point. In the
450example above, git may think of the branch named "A" as just a
451pointer to one particular commit, but we may refer informally to the
452line of three commits leading up to that point as all being part of
453"branch A".
454
455If we need to make it clear that we're just talking about the most
456recent commit on the branch, we may refer to that commit as the
457"head" of the branch.
458
459Manipulating branches
460---------------------
461
462Creating, deleting, and modifying branches is quick and easy; here's
463a summary of the commands:
464
465git branch::
466 list all branches
467git branch <branch>::
468 create a new branch named <branch>, referencing the same
469 point in history as the current branch
470git branch <branch> <start-point>::
471 create a new branch named <branch>, referencing
472 <start-point>, which may be specified any way you like,
473 including using a branch name or a tag name
474git branch -d <branch>::
475 delete the branch <branch>; if the branch you are deleting
476 points to a commit which is not reachable from this branch,
477 this command will fail with a warning.
478git branch -D <branch>::
479 even if the branch points to a commit not reachable
480 from the current branch, you may know that that commit
481 is still reachable from some other branch or tag. In that
482 case it is safe to use this command to force git to delete
483 the branch.
484git checkout <branch>::
485 make the current branch <branch>, updating the working
486 directory to reflect the version referenced by <branch>
487git checkout -b <new> <start-point>::
488 create a new branch <new> referencing <start-point>, and
489 check it out.
490
491It is also useful to know that the special symbol "HEAD" can always
492be used to refer to the current branch.
493
494Examining branches from a remote repository
495-------------------------------------------
496
497The "master" branch that was created at the time you cloned is a copy
498of the HEAD in the repository that you cloned from. That repository
499may also have had other branches, though, and your local repository
500keeps branches which track each of those remote branches, which you
501can view using the "-r" option to gitlink:git-branch[1]:
502
503------------------------------------------------
504$ git branch -r
505 origin/HEAD
506 origin/html
507 origin/maint
508 origin/man
509 origin/master
510 origin/next
511 origin/pu
512 origin/todo
513------------------------------------------------
514
515You cannot check out these remote-tracking branches, but you can
516examine them on a branch of your own, just as you would a tag:
517
518------------------------------------------------
519$ git checkout -b my-todo-copy origin/todo
520------------------------------------------------
521
522Note that the name "origin" is just the name that git uses by default
523to refer to the repository that you cloned from.
524
525[[how-git-stores-references]]
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526Naming branches, tags, and other references
527-------------------------------------------
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528
529Branches, remote-tracking branches, and tags are all references to
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530commits. All references are named with a slash-separated path name
531starting with "refs"; the names we've been using so far are actually
532shorthand:
d19fbc3c 533
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534 - The branch "test" is short for "refs/heads/test".
535 - The tag "v2.6.18" is short for "refs/tags/v2.6.18".
536 - "origin/master" is short for "refs/remotes/origin/master".
d19fbc3c 537
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538The full name is occasionally useful if, for example, there ever
539exists a tag and a branch with the same name.
d19fbc3c 540
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541As another useful shortcut, if the repository "origin" posesses only
542a single branch, you can refer to that branch as just "origin".
d19fbc3c 543
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544More generally, if you have defined a remote repository named
545"example", you can refer to the branch in that repository as
546"example". And for a repository with multiple branches, this will
547refer to the branch designated as the "HEAD" branch.
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548
549For the complete list of paths which git checks for references, and
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550the order it uses to decide which to choose when there are multiple
551references with the same shorthand name, see the "SPECIFYING
552REVISIONS" section of gitlink:git-rev-parse[1].
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553
554[[Updating-a-repository-with-git-fetch]]
555Updating a repository with git fetch
556------------------------------------
557
558Eventually the developer cloned from will do additional work in her
559repository, creating new commits and advancing the branches to point
560at the new commits.
561
562The command "git fetch", with no arguments, will update all of the
563remote-tracking branches to the latest version found in her
564repository. It will not touch any of your own branches--not even the
565"master" branch that was created for you on clone.
566
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567Fetching branches from other repositories
568-----------------------------------------
569
570You can also track branches from repositories other than the one you
571cloned from, using gitlink:git-remote[1]:
572
573-------------------------------------------------
574$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git
575$ git fetch
576* refs/remotes/linux-nfs/master: storing branch 'master' ...
577 commit: bf81b46
578-------------------------------------------------
579
580New remote-tracking branches will be stored under the shorthand name
581that you gave "git remote add", in this case linux-nfs:
582
583-------------------------------------------------
584$ git branch -r
585linux-nfs/master
586origin/master
587-------------------------------------------------
588
589If you run "git fetch <remote>" later, the tracking branches for the
590named <remote> will be updated.
591
592If you examine the file .git/config, you will see that git has added
593a new stanza:
594
595-------------------------------------------------
596$ cat .git/config
597...
598[remote "linux-nfs"]
599 url = git://linux-nfs.org/~bfields/git.git
600 fetch = +refs/heads/*:refs/remotes/linux-nfs-read/*
601...
602-------------------------------------------------
603
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604This is what causes git to track the remote's branches; you may modify
605or delete these configuration options by editing .git/config with a
606text editor. (See the "CONFIGURATION FILE" section of
607gitlink:git-config[1] for details.)
d5cd5de4 608
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609Exploring git history
610=====================
611
612Git is best thought of as a tool for storing the history of a
613collection of files. It does this by storing compressed snapshots of
614the contents of a file heirarchy, together with "commits" which show
615the relationships between these snapshots.
616
617Git provides extremely flexible and fast tools for exploring the
618history of a project.
619
aacd404e 620We start with one specialized tool that is useful for finding the
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621commit that introduced a bug into a project.
622
623How to use bisect to find a regression
624--------------------------------------
625
626Suppose version 2.6.18 of your project worked, but the version at
627"master" crashes. Sometimes the best way to find the cause of such a
628regression is to perform a brute-force search through the project's
629history to find the particular commit that caused the problem. The
630gitlink:git-bisect[1] command can help you do this:
631
632-------------------------------------------------
633$ git bisect start
634$ git bisect good v2.6.18
635$ git bisect bad master
636Bisecting: 3537 revisions left to test after this
637[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]
638-------------------------------------------------
639
640If you run "git branch" at this point, you'll see that git has
641temporarily moved you to a new branch named "bisect". This branch
642points to a commit (with commit id 65934...) that is reachable from
643v2.6.19 but not from v2.6.18. Compile and test it, and see whether
644it crashes. Assume it does crash. Then:
645
646-------------------------------------------------
647$ git bisect bad
648Bisecting: 1769 revisions left to test after this
649[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
650-------------------------------------------------
651
652checks out an older version. Continue like this, telling git at each
653stage whether the version it gives you is good or bad, and notice
654that the number of revisions left to test is cut approximately in
655half each time.
656
657After about 13 tests (in this case), it will output the commit id of
658the guilty commit. You can then examine the commit with
659gitlink:git-show[1], find out who wrote it, and mail them your bug
660report with the commit id. Finally, run
661
662-------------------------------------------------
663$ git bisect reset
664-------------------------------------------------
665
666to return you to the branch you were on before and delete the
667temporary "bisect" branch.
668
669Note that the version which git-bisect checks out for you at each
670point is just a suggestion, and you're free to try a different
671version if you think it would be a good idea. For example,
672occasionally you may land on a commit that broke something unrelated;
673run
674
675-------------------------------------------------
676$ git bisect-visualize
677-------------------------------------------------
678
679which will run gitk and label the commit it chose with a marker that
680says "bisect". Chose a safe-looking commit nearby, note its commit
681id, and check it out with:
682
683-------------------------------------------------
684$ git reset --hard fb47ddb2db...
685-------------------------------------------------
686
687then test, run "bisect good" or "bisect bad" as appropriate, and
688continue.
689
690Naming commits
691--------------
692
693We have seen several ways of naming commits already:
694
d55ae921 695 - 40-hexdigit object name
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696 - branch name: refers to the commit at the head of the given
697 branch
698 - tag name: refers to the commit pointed to by the given tag
699 (we've seen branches and tags are special cases of
700 <<how-git-stores-references,references>>).
701 - HEAD: refers to the head of the current branch
702
eb6ae7f4 703There are many more; see the "SPECIFYING REVISIONS" section of the
aec053bb 704gitlink:git-rev-parse[1] man page for the complete list of ways to
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705name revisions. Some examples:
706
707-------------------------------------------------
d55ae921 708$ git show fb47ddb2 # the first few characters of the object name
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709 # are usually enough to specify it uniquely
710$ git show HEAD^ # the parent of the HEAD commit
711$ git show HEAD^^ # the grandparent
712$ git show HEAD~4 # the great-great-grandparent
713-------------------------------------------------
714
715Recall that merge commits may have more than one parent; by default,
716^ and ~ follow the first parent listed in the commit, but you can
717also choose:
718
719-------------------------------------------------
720$ git show HEAD^1 # show the first parent of HEAD
721$ git show HEAD^2 # show the second parent of HEAD
722-------------------------------------------------
723
724In addition to HEAD, there are several other special names for
725commits:
726
727Merges (to be discussed later), as well as operations such as
728git-reset, which change the currently checked-out commit, generally
729set ORIG_HEAD to the value HEAD had before the current operation.
730
731The git-fetch operation always stores the head of the last fetched
732branch in FETCH_HEAD. For example, if you run git fetch without
733specifying a local branch as the target of the operation
734
735-------------------------------------------------
736$ git fetch git://example.com/proj.git theirbranch
737-------------------------------------------------
738
739the fetched commits will still be available from FETCH_HEAD.
740
741When we discuss merges we'll also see the special name MERGE_HEAD,
742which refers to the other branch that we're merging in to the current
743branch.
744
aec053bb 745The gitlink:git-rev-parse[1] command is a low-level command that is
d55ae921
BF
746occasionally useful for translating some name for a commit to the object
747name for that commit:
aec053bb
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748
749-------------------------------------------------
750$ git rev-parse origin
751e05db0fd4f31dde7005f075a84f96b360d05984b
752-------------------------------------------------
753
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754Creating tags
755-------------
756
757We can also create a tag to refer to a particular commit; after
758running
759
760-------------------------------------------------
761$ git-tag stable-1 1b2e1d63ff
762-------------------------------------------------
763
764You can use stable-1 to refer to the commit 1b2e1d63ff.
765
766This creates a "lightweight" tag. If the tag is a tag you wish to
767share with others, and possibly sign cryptographically, then you
768should create a tag object instead; see the gitlink:git-tag[1] man
769page for details.
770
771Browsing revisions
772------------------
773
774The gitlink:git-log[1] command can show lists of commits. On its
775own, it shows all commits reachable from the parent commit; but you
776can also make more specific requests:
777
778-------------------------------------------------
779$ git log v2.5.. # commits since (not reachable from) v2.5
780$ git log test..master # commits reachable from master but not test
781$ git log master..test # ...reachable from test but not master
782$ git log master...test # ...reachable from either test or master,
783 # but not both
784$ git log --since="2 weeks ago" # commits from the last 2 weeks
785$ git log Makefile # commits which modify Makefile
786$ git log fs/ # ... which modify any file under fs/
787$ git log -S'foo()' # commits which add or remove any file data
788 # matching the string 'foo()'
789-------------------------------------------------
790
791And of course you can combine all of these; the following finds
792commits since v2.5 which touch the Makefile or any file under fs:
793
794-------------------------------------------------
795$ git log v2.5.. Makefile fs/
796-------------------------------------------------
797
798You can also ask git log to show patches:
799
800-------------------------------------------------
801$ git log -p
802-------------------------------------------------
803
804See the "--pretty" option in the gitlink:git-log[1] man page for more
805display options.
806
807Note that git log starts with the most recent commit and works
808backwards through the parents; however, since git history can contain
3dff5379 809multiple independent lines of development, the particular order that
d19fbc3c
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810commits are listed in may be somewhat arbitrary.
811
812Generating diffs
813----------------
814
815You can generate diffs between any two versions using
816gitlink:git-diff[1]:
817
818-------------------------------------------------
819$ git diff master..test
820-------------------------------------------------
821
822Sometimes what you want instead is a set of patches:
823
824-------------------------------------------------
825$ git format-patch master..test
826-------------------------------------------------
827
828will generate a file with a patch for each commit reachable from test
829but not from master. Note that if master also has commits which are
830not reachable from test, then the combined result of these patches
831will not be the same as the diff produced by the git-diff example.
832
833Viewing old file versions
834-------------------------
835
836You can always view an old version of a file by just checking out the
837correct revision first. But sometimes it is more convenient to be
838able to view an old version of a single file without checking
839anything out; this command does that:
840
841-------------------------------------------------
842$ git show v2.5:fs/locks.c
843-------------------------------------------------
844
845Before the colon may be anything that names a commit, and after it
846may be any path to a file tracked by git.
847
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848Examples
849--------
850
851Check whether two branches point at the same history
2f99710c 852~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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853
854Suppose you want to check whether two branches point at the same point
855in history.
856
857-------------------------------------------------
858$ git diff origin..master
859-------------------------------------------------
860
69f7ad73
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861will tell you whether the contents of the project are the same at the
862two branches; in theory, however, it's possible that the same project
863contents could have been arrived at by two different historical
d55ae921 864routes. You could compare the object names:
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865
866-------------------------------------------------
867$ git rev-list origin
868e05db0fd4f31dde7005f075a84f96b360d05984b
869$ git rev-list master
870e05db0fd4f31dde7005f075a84f96b360d05984b
871-------------------------------------------------
872
69f7ad73
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873Or you could recall that the ... operator selects all commits
874contained reachable from either one reference or the other but not
875both: so
aec053bb
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876
877-------------------------------------------------
878$ git log origin...master
879-------------------------------------------------
880
881will return no commits when the two branches are equal.
882
b181d57f
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883Find first tagged version including a given fix
884~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
aec053bb 885
69f7ad73
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886Suppose you know that the commit e05db0fd fixed a certain problem.
887You'd like to find the earliest tagged release that contains that
888fix.
889
890Of course, there may be more than one answer--if the history branched
891after commit e05db0fd, then there could be multiple "earliest" tagged
892releases.
893
894You could just visually inspect the commits since e05db0fd:
895
896-------------------------------------------------
897$ gitk e05db0fd..
898-------------------------------------------------
899
b181d57f
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900Or you can use gitlink:git-name-rev[1], which will give the commit a
901name based on any tag it finds pointing to one of the commit's
902descendants:
903
904-------------------------------------------------
905$ git name-rev e05db0fd
906e05db0fd tags/v1.5.0-rc1^0~23
907-------------------------------------------------
908
909The gitlink:git-describe[1] command does the opposite, naming the
910revision using a tag on which the given commit is based:
911
912-------------------------------------------------
913$ git describe e05db0fd
914v1.5.0-rc0-ge05db0f
915-------------------------------------------------
916
917but that may sometimes help you guess which tags might come after the
918given commit.
919
920If you just want to verify whether a given tagged version contains a
921given commit, you could use gitlink:git-merge-base[1]:
922
923-------------------------------------------------
924$ git merge-base e05db0fd v1.5.0-rc1
925e05db0fd4f31dde7005f075a84f96b360d05984b
926-------------------------------------------------
927
928The merge-base command finds a common ancestor of the given commits,
929and always returns one or the other in the case where one is a
930descendant of the other; so the above output shows that e05db0fd
931actually is an ancestor of v1.5.0-rc1.
932
933Alternatively, note that
934
935-------------------------------------------------
4a7979ca 936$ git log v1.5.0-rc1..e05db0fd
b181d57f
BF
937-------------------------------------------------
938
4a7979ca 939will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
b181d57f 940because it outputs only commits that are not reachable from v1.5.0-rc1.
aec053bb 941
4a7979ca
BF
942As yet another alternative, the gitlink:git-show-branch[1] command lists
943the commits reachable from its arguments with a display on the left-hand
944side that indicates which arguments that commit is reachable from. So,
945you can run something like
946
947-------------------------------------------------
948$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
949! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
950available
951 ! [v1.5.0-rc0] GIT v1.5.0 preview
952 ! [v1.5.0-rc1] GIT v1.5.0-rc1
953 ! [v1.5.0-rc2] GIT v1.5.0-rc2
954...
955-------------------------------------------------
956
957then search for a line that looks like
958
959-------------------------------------------------
960+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
961available
962-------------------------------------------------
963
964Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and
965from v1.5.0-rc2, but not from v1.5.0-rc0.
966
967
d19fbc3c
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968Developing with git
969===================
970
971Telling git your name
972---------------------
973
974Before creating any commits, you should introduce yourself to git. The
975easiest way to do so is:
976
977------------------------------------------------
978$ cat >~/.gitconfig <<\EOF
979[user]
980 name = Your Name Comes Here
981 email = you@yourdomain.example.com
982EOF
983------------------------------------------------
984
fc90c536
BF
985(See the "CONFIGURATION FILE" section of gitlink:git-config[1] for
986details on the configuration file.)
987
d19fbc3c
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988
989Creating a new repository
990-------------------------
991
992Creating a new repository from scratch is very easy:
993
994-------------------------------------------------
995$ mkdir project
996$ cd project
f1d2b477 997$ git init
d19fbc3c
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998-------------------------------------------------
999
1000If you have some initial content (say, a tarball):
1001
1002-------------------------------------------------
1003$ tar -xzvf project.tar.gz
1004$ cd project
f1d2b477 1005$ git init
d19fbc3c
BF
1006$ git add . # include everything below ./ in the first commit:
1007$ git commit
1008-------------------------------------------------
1009
1010[[how-to-make-a-commit]]
1011how to make a commit
1012--------------------
1013
1014Creating a new commit takes three steps:
1015
1016 1. Making some changes to the working directory using your
1017 favorite editor.
1018 2. Telling git about your changes.
1019 3. Creating the commit using the content you told git about
1020 in step 2.
1021
1022In practice, you can interleave and repeat steps 1 and 2 as many
1023times as you want: in order to keep track of what you want committed
1024at step 3, git maintains a snapshot of the tree's contents in a
1025special staging area called "the index."
1026
01997b4a
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1027At the beginning, the content of the index will be identical to
1028that of the HEAD. The command "git diff --cached", which shows
1029the difference between the HEAD and the index, should therefore
1030produce no output at that point.
eb6ae7f4 1031
d19fbc3c
BF
1032Modifying the index is easy:
1033
1034To update the index with the new contents of a modified file, use
1035
1036-------------------------------------------------
1037$ git add path/to/file
1038-------------------------------------------------
1039
1040To add the contents of a new file to the index, use
1041
1042-------------------------------------------------
1043$ git add path/to/file
1044-------------------------------------------------
1045
eb6ae7f4 1046To remove a file from the index and from the working tree,
d19fbc3c
BF
1047
1048-------------------------------------------------
1049$ git rm path/to/file
1050-------------------------------------------------
1051
1052After each step you can verify that
1053
1054-------------------------------------------------
1055$ git diff --cached
1056-------------------------------------------------
1057
1058always shows the difference between the HEAD and the index file--this
1059is what you'd commit if you created the commit now--and that
1060
1061-------------------------------------------------
1062$ git diff
1063-------------------------------------------------
1064
1065shows the difference between the working tree and the index file.
1066
1067Note that "git add" always adds just the current contents of a file
1068to the index; further changes to the same file will be ignored unless
1069you run git-add on the file again.
1070
1071When you're ready, just run
1072
1073-------------------------------------------------
1074$ git commit
1075-------------------------------------------------
1076
1077and git will prompt you for a commit message and then create the new
3dff5379 1078commit. Check to make sure it looks like what you expected with
d19fbc3c
BF
1079
1080-------------------------------------------------
1081$ git show
1082-------------------------------------------------
1083
1084As a special shortcut,
1085
1086-------------------------------------------------
1087$ git commit -a
1088-------------------------------------------------
1089
1090will update the index with any files that you've modified or removed
1091and create a commit, all in one step.
1092
1093A number of commands are useful for keeping track of what you're
1094about to commit:
1095
1096-------------------------------------------------
1097$ git diff --cached # difference between HEAD and the index; what
1098 # would be commited if you ran "commit" now.
1099$ git diff # difference between the index file and your
1100 # working directory; changes that would not
1101 # be included if you ran "commit" now.
1102$ git status # a brief per-file summary of the above.
1103-------------------------------------------------
1104
1105creating good commit messages
1106-----------------------------
1107
1108Though not required, it's a good idea to begin the commit message
1109with a single short (less than 50 character) line summarizing the
1110change, followed by a blank line and then a more thorough
1111description. Tools that turn commits into email, for example, use
1112the first line on the Subject line and the rest of the commit in the
1113body.
1114
1115how to merge
1116------------
1117
1118You can rejoin two diverging branches of development using
1119gitlink:git-merge[1]:
1120
1121-------------------------------------------------
1122$ git merge branchname
1123-------------------------------------------------
1124
1125merges the development in the branch "branchname" into the current
1126branch. If there are conflicts--for example, if the same file is
1127modified in two different ways in the remote branch and the local
1128branch--then you are warned; the output may look something like this:
1129
1130-------------------------------------------------
1131$ git pull . next
1132Trying really trivial in-index merge...
1133fatal: Merge requires file-level merging
1134Nope.
1135Merging HEAD with 77976da35a11db4580b80ae27e8d65caf5208086
1136Merging:
113715e2162 world
113877976da goodbye
1139found 1 common ancestor(s):
1140d122ed4 initial
1141Auto-merging file.txt
1142CONFLICT (content): Merge conflict in file.txt
1143Automatic merge failed; fix conflicts and then commit the result.
1144-------------------------------------------------
1145
1146Conflict markers are left in the problematic files, and after
1147you resolve the conflicts manually, you can update the index
1148with the contents and run git commit, as you normally would when
1149creating a new file.
1150
1151If you examine the resulting commit using gitk, you will see that it
1152has two parents, one pointing to the top of the current branch, and
1153one to the top of the other branch.
1154
1155In more detail:
1156
1157[[resolving-a-merge]]
1158Resolving a merge
1159-----------------
1160
1161When a merge isn't resolved automatically, git leaves the index and
1162the working tree in a special state that gives you all the
1163information you need to help resolve the merge.
1164
1165Files with conflicts are marked specially in the index, so until you
1166resolve the problem and update the index, git commit will fail:
1167
1168-------------------------------------------------
1169$ git commit
1170file.txt: needs merge
1171-------------------------------------------------
1172
1173Also, git status will list those files as "unmerged".
1174
1175All of the changes that git was able to merge automatically are
1176already added to the index file, so gitlink:git-diff[1] shows only
1177the conflicts. Also, it uses a somewhat unusual syntax:
1178
1179-------------------------------------------------
1180$ git diff
1181diff --cc file.txt
1182index 802992c,2b60207..0000000
1183--- a/file.txt
1184+++ b/file.txt
1185@@@ -1,1 -1,1 +1,5 @@@
1186++<<<<<<< HEAD:file.txt
1187 +Hello world
1188++=======
1189+ Goodbye
1190++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
1191-------------------------------------------------
1192
1193Recall that the commit which will be commited after we resolve this
1194conflict will have two parents instead of the usual one: one parent
1195will be HEAD, the tip of the current branch; the other will be the
1196tip of the other branch, which is stored temporarily in MERGE_HEAD.
1197
1198The diff above shows the differences between the working-tree version
1199of file.txt and two previous version: one version from HEAD, and one
1200from MERGE_HEAD. So instead of preceding each line by a single "+"
1201or "-", it now uses two columns: the first column is used for
1202differences between the first parent and the working directory copy,
1203and the second for differences between the second parent and the
1204working directory copy. Thus after resolving the conflict in the
1205obvious way, the diff will look like:
1206
1207-------------------------------------------------
1208$ git diff
1209diff --cc file.txt
1210index 802992c,2b60207..0000000
1211--- a/file.txt
1212+++ b/file.txt
1213@@@ -1,1 -1,1 +1,1 @@@
1214- Hello world
1215 -Goodbye
1216++Goodbye world
1217-------------------------------------------------
1218
1219This shows that our resolved version deleted "Hello world" from the
1220first parent, deleted "Goodbye" from the second parent, and added
1221"Goodbye world", which was previously absent from both.
1222
1223The gitlink:git-log[1] command also provides special help for merges:
1224
1225-------------------------------------------------
1226$ git log --merge
1227-------------------------------------------------
1228
1229This will list all commits which exist only on HEAD or on MERGE_HEAD,
1230and which touch an unmerged file.
1231
1232We can now add the resolved version to the index and commit:
1233
1234-------------------------------------------------
1235$ git add file.txt
1236$ git commit
1237-------------------------------------------------
1238
1239Note that the commit message will already be filled in for you with
1240some information about the merge. Normally you can just use this
1241default message unchanged, but you may add additional commentary of
1242your own if desired.
1243
1244[[undoing-a-merge]]
1245undoing a merge
1246---------------
1247
1248If you get stuck and decide to just give up and throw the whole mess
1249away, you can always return to the pre-merge state with
1250
1251-------------------------------------------------
1252$ git reset --hard HEAD
1253-------------------------------------------------
1254
1255Or, if you've already commited the merge that you want to throw away,
1256
1257-------------------------------------------------
1258$ git reset --hard HEAD^
1259-------------------------------------------------
1260
1261However, this last command can be dangerous in some cases--never
1262throw away a commit you have already committed if that commit may
1263itself have been merged into another branch, as doing so may confuse
1264further merges.
1265
1266Fast-forward merges
1267-------------------
1268
1269There is one special case not mentioned above, which is treated
1270differently. Normally, a merge results in a merge commit, with two
1271parents, one pointing at each of the two lines of development that
1272were merged.
1273
1274However, if one of the two lines of development is completely
1275contained within the other--so every commit present in the one is
1276already contained in the other--then git just performs a
1277<<fast-forwards,fast forward>>; the head of the current branch is
1278moved forward to point at the head of the merged-in branch, without
1279any new commits being created.
1280
b684f830
BF
1281Fixing mistakes
1282---------------
1283
1284If you've messed up the working tree, but haven't yet committed your
1285mistake, you can return the entire working tree to the last committed
1286state with
1287
1288-------------------------------------------------
1289$ git reset --hard HEAD
1290-------------------------------------------------
1291
1292If you make a commit that you later wish you hadn't, there are two
1293fundamentally different ways to fix the problem:
1294
1295 1. You can create a new commit that undoes whatever was done
1296 by the previous commit. This is the correct thing if your
1297 mistake has already been made public.
1298
1299 2. You can go back and modify the old commit. You should
1300 never do this if you have already made the history public;
1301 git does not normally expect the "history" of a project to
1302 change, and cannot correctly perform repeated merges from
1303 a branch that has had its history changed.
1304
1305Fixing a mistake with a new commit
1306~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1307
1308Creating a new commit that reverts an earlier change is very easy;
1309just pass the gitlink:git-revert[1] command a reference to the bad
1310commit; for example, to revert the most recent commit:
1311
1312-------------------------------------------------
1313$ git revert HEAD
1314-------------------------------------------------
1315
1316This will create a new commit which undoes the change in HEAD. You
1317will be given a chance to edit the commit message for the new commit.
1318
1319You can also revert an earlier change, for example, the next-to-last:
1320
1321-------------------------------------------------
1322$ git revert HEAD^
1323-------------------------------------------------
1324
1325In this case git will attempt to undo the old change while leaving
1326intact any changes made since then. If more recent changes overlap
1327with the changes to be reverted, then you will be asked to fix
1328conflicts manually, just as in the case of <<resolving-a-merge,
1329resolving a merge>>.
1330
1331Fixing a mistake by editing history
1332~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1333
1334If the problematic commit is the most recent commit, and you have not
1335yet made that commit public, then you may just
1336<<undoing-a-merge,destroy it using git-reset>>.
1337
1338Alternatively, you
1339can edit the working directory and update the index to fix your
1340mistake, just as if you were going to <<how-to-make-a-commit,create a
1341new commit>>, then run
1342
1343-------------------------------------------------
1344$ git commit --amend
1345-------------------------------------------------
1346
1347which will replace the old commit by a new commit incorporating your
1348changes, giving you a chance to edit the old commit message first.
1349
1350Again, you should never do this to a commit that may already have
1351been merged into another branch; use gitlink:git-revert[1] instead in
1352that case.
1353
1354It is also possible to edit commits further back in the history, but
1355this is an advanced topic to be left for
1356<<cleaning-up-history,another chapter>>.
1357
1358Checking out an old version of a file
1359~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1360
1361In the process of undoing a previous bad change, you may find it
1362useful to check out an older version of a particular file using
1363gitlink:git-checkout[1]. We've used git checkout before to switch
1364branches, but it has quite different behavior if it is given a path
1365name: the command
1366
1367-------------------------------------------------
1368$ git checkout HEAD^ path/to/file
1369-------------------------------------------------
1370
1371replaces path/to/file by the contents it had in the commit HEAD^, and
1372also updates the index to match. It does not change branches.
1373
1374If you just want to look at an old version of the file, without
1375modifying the working directory, you can do that with
1376gitlink:git-show[1]:
1377
1378-------------------------------------------------
1379$ git show HEAD^ path/to/file
1380-------------------------------------------------
1381
1382which will display the given version of the file.
1383
d19fbc3c
BF
1384Ensuring good performance
1385-------------------------
1386
1387On large repositories, git depends on compression to keep the history
1388information from taking up to much space on disk or in memory.
1389
1390This compression is not performed automatically. Therefore you
17217090 1391should occasionally run gitlink:git-gc[1]:
d19fbc3c
BF
1392
1393-------------------------------------------------
1394$ git gc
1395-------------------------------------------------
1396
17217090
BF
1397to recompress the archive. This can be very time-consuming, so
1398you may prefer to run git-gc when you are not doing other work.
d19fbc3c 1399
11e016a3
BF
1400Ensuring reliability
1401--------------------
1402
1403Checking the repository for corruption
1404~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1405
1191ee18
BF
1406The gitlink:git-fsck[1] command runs a number of self-consistency checks
1407on the repository, and reports on any problems. This may take some
21dcb3b7
BF
1408time. The most common warning by far is about "dangling" objects:
1409
1410-------------------------------------------------
04e50e94 1411$ git fsck
21dcb3b7
BF
1412dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1413dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1414dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1415dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
1416dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
1417dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
1418dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
1419dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
1420...
1421-------------------------------------------------
1422
1191ee18
BF
1423Dangling objects are objects that are harmless, but also unnecessary;
1424you can remove them at any time with gitlink:git-prune[1] or the --prune
1425option to gitlink:git-gc[1]:
21dcb3b7
BF
1426
1427-------------------------------------------------
1428$ git gc --prune
1429-------------------------------------------------
1430
1191ee18
BF
1431This may be time-consuming. Unlike most other git operations (including
1432git-gc when run without any options), it is not safe to prune while
1433other git operations are in progress in the same repository.
21dcb3b7 1434
988b27d3 1435For more about dangling objects, see <<dangling-objects>>.
21dcb3b7 1436
11e016a3
BF
1437
1438Recovering lost changes
1439~~~~~~~~~~~~~~~~~~~~~~~
1440
559e4d7a
BF
1441Reflogs
1442^^^^^^^
1443
1444Say you modify a branch with gitlink:git-reset[1] --hard, and then
1445realize that the branch was the only reference you had to that point in
1446history.
1447
1448Fortunately, git also keeps a log, called a "reflog", of all the
1449previous values of each branch. So in this case you can still find the
1450old history using, for example,
1451
1452-------------------------------------------------
1453$ git log master@{1}
1454-------------------------------------------------
1455
1456This lists the commits reachable from the previous version of the head.
1457This syntax can be used to with any git command that accepts a commit,
1458not just with git log. Some other examples:
1459
1460-------------------------------------------------
1461$ git show master@{2} # See where the branch pointed 2,
1462$ git show master@{3} # 3, ... changes ago.
1463$ gitk master@{yesterday} # See where it pointed yesterday,
1464$ gitk master@{"1 week ago"} # ... or last week
1465-------------------------------------------------
1466
1467The reflogs are kept by default for 30 days, after which they may be
036be17e 1468pruned. See gitlink:git-reflog[1] and gitlink:git-gc[1] to learn
559e4d7a
BF
1469how to control this pruning, and see the "SPECIFYING REVISIONS"
1470section of gitlink:git-rev-parse[1] for details.
1471
1472Note that the reflog history is very different from normal git history.
1473While normal history is shared by every repository that works on the
1474same project, the reflog history is not shared: it tells you only about
1475how the branches in your local repository have changed over time.
1476
1477Examining dangling objects
1478^^^^^^^^^^^^^^^^^^^^^^^^^^
1479
1480In some situations the reflog may not be able to save you. For
1481example, suppose you delete a branch, then realize you need the history
1482it pointed you. The reflog is also deleted; however, if you have not
1483yet pruned the repository, then you may still be able to find
1484the lost commits; run git-fsck and watch for output that mentions
1485"dangling commits":
1486
1487-------------------------------------------------
1488$ git fsck
1489dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1490dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1491dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1492...
1493-------------------------------------------------
1494
aacd404e 1495You can examine
559e4d7a
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1496one of those dangling commits with, for example,
1497
1498------------------------------------------------
1499$ gitk 7281251ddd --not --all
1500------------------------------------------------
1501
1502which does what it sounds like: it says that you want to see the commit
1503history that is described by the dangling commit(s), but not the
1504history that is described by all your existing branches and tags. Thus
1505you get exactly the history reachable from that commit that is lost.
1506(And notice that it might not be just one commit: we only report the
1507"tip of the line" as being dangling, but there might be a whole deep
1508and complex commit history that was gotten dropped.)
1509
1510If you decide you want the history back, you can always create a new
1511reference pointing to it, for example, a new branch:
1512
1513------------------------------------------------
1514$ git branch recovered-branch 7281251ddd
1515------------------------------------------------
1516
11e016a3 1517
d19fbc3c 1518Sharing development with others
b684f830 1519===============================
d19fbc3c
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1520
1521[[getting-updates-with-git-pull]]
1522Getting updates with git pull
b684f830 1523-----------------------------
d19fbc3c
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1524
1525After you clone a repository and make a few changes of your own, you
1526may wish to check the original repository for updates and merge them
1527into your own work.
1528
1529We have already seen <<Updating-a-repository-with-git-fetch,how to
1530keep remote tracking branches up to date>> with gitlink:git-fetch[1],
1531and how to merge two branches. So you can merge in changes from the
1532original repository's master branch with:
1533
1534-------------------------------------------------
1535$ git fetch
1536$ git merge origin/master
1537-------------------------------------------------
1538
1539However, the gitlink:git-pull[1] command provides a way to do this in
1540one step:
1541
1542-------------------------------------------------
1543$ git pull origin master
1544-------------------------------------------------
1545
1546In fact, "origin" is normally the default repository to pull from,
1547and the default branch is normally the HEAD of the remote repository,
1548so often you can accomplish the above with just
1549
1550-------------------------------------------------
1551$ git pull
1552-------------------------------------------------
1553
1554See the descriptions of the branch.<name>.remote and
9d13bda3 1555branch.<name>.merge options in gitlink:git-config[1] to learn
d19fbc3c
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1556how to control these defaults depending on the current branch.
1557
1558In addition to saving you keystrokes, "git pull" also helps you by
1559producing a default commit message documenting the branch and
1560repository that you pulled from.
1561
1562(But note that no such commit will be created in the case of a
1563<<fast-forwards,fast forward>>; instead, your branch will just be
1564updated to point to the latest commit from the upstream branch).
1565
1191ee18
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1566The git-pull command can also be given "." as the "remote" repository,
1567in which case it just merges in a branch from the current repository; so
4c63ff45
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1568the commands
1569
1570-------------------------------------------------
1571$ git pull . branch
1572$ git merge branch
1573-------------------------------------------------
1574
1575are roughly equivalent. The former is actually very commonly used.
1576
d19fbc3c 1577Submitting patches to a project
b684f830 1578-------------------------------
d19fbc3c
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1579
1580If you just have a few changes, the simplest way to submit them may
1581just be to send them as patches in email:
1582
036be17e 1583First, use gitlink:git-format-patch[1]; for example:
d19fbc3c
BF
1584
1585-------------------------------------------------
eb6ae7f4 1586$ git format-patch origin
d19fbc3c
BF
1587-------------------------------------------------
1588
1589will produce a numbered series of files in the current directory, one
1590for each patch in the current branch but not in origin/HEAD.
1591
1592You can then import these into your mail client and send them by
1593hand. However, if you have a lot to send at once, you may prefer to
1594use the gitlink:git-send-email[1] script to automate the process.
1595Consult the mailing list for your project first to determine how they
1596prefer such patches be handled.
1597
1598Importing patches to a project
b684f830 1599------------------------------
d19fbc3c
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1600
1601Git also provides a tool called gitlink:git-am[1] (am stands for
1602"apply mailbox"), for importing such an emailed series of patches.
1603Just save all of the patch-containing messages, in order, into a
1604single mailbox file, say "patches.mbox", then run
1605
1606-------------------------------------------------
eb6ae7f4 1607$ git am -3 patches.mbox
d19fbc3c
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1608-------------------------------------------------
1609
1610Git will apply each patch in order; if any conflicts are found, it
1611will stop, and you can fix the conflicts as described in
01997b4a
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1612"<<resolving-a-merge,Resolving a merge>>". (The "-3" option tells
1613git to perform a merge; if you would prefer it just to abort and
1614leave your tree and index untouched, you may omit that option.)
1615
1616Once the index is updated with the results of the conflict
1617resolution, instead of creating a new commit, just run
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BF
1618
1619-------------------------------------------------
1620$ git am --resolved
1621-------------------------------------------------
1622
1623and git will create the commit for you and continue applying the
1624remaining patches from the mailbox.
1625
1626The final result will be a series of commits, one for each patch in
1627the original mailbox, with authorship and commit log message each
1628taken from the message containing each patch.
1629
1630[[setting-up-a-public-repository]]
1631Setting up a public repository
b684f830 1632------------------------------
d19fbc3c
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1633
1634Another way to submit changes to a project is to simply tell the
1635maintainer of that project to pull from your repository, exactly as
1636you did in the section "<<getting-updates-with-git-pull, Getting
1637updates with git pull>>".
1638
1639If you and maintainer both have accounts on the same machine, then
1640then you can just pull changes from each other's repositories
1641directly; note that all of the command (gitlink:git-clone[1],
1642git-fetch[1], git-pull[1], etc.) which accept a URL as an argument
1643will also accept a local file patch; so, for example, you can
1644use
1645
1646-------------------------------------------------
1647$ git clone /path/to/repository
1648$ git pull /path/to/other/repository
1649-------------------------------------------------
1650
1651If this sort of setup is inconvenient or impossible, another (more
1652common) option is to set up a public repository on a public server.
1653This also allows you to cleanly separate private work in progress
1654from publicly visible work.
1655
1656You will continue to do your day-to-day work in your personal
1657repository, but periodically "push" changes from your personal
1658repository into your public repository, allowing other developers to
1659pull from that repository. So the flow of changes, in a situation
1660where there is one other developer with a public repository, looks
1661like this:
1662
1663 you push
1664 your personal repo ------------------> your public repo
1665 ^ |
1666 | |
1667 | you pull | they pull
1668 | |
1669 | |
1670 | they push V
1671 their public repo <------------------- their repo
1672
1673Now, assume your personal repository is in the directory ~/proj. We
1674first create a new clone of the repository:
1675
1676-------------------------------------------------
1677$ git clone --bare proj-clone.git
1678-------------------------------------------------
1679
1680The resulting directory proj-clone.git will contains a "bare" git
1681repository--it is just the contents of the ".git" directory, without
1682a checked-out copy of a working directory.
1683
1684Next, copy proj-clone.git to the server where you plan to host the
1685public repository. You can use scp, rsync, or whatever is most
1686convenient.
1687
1688If somebody else maintains the public server, they may already have
1689set up a git service for you, and you may skip to the section
1690"<<pushing-changes-to-a-public-repository,Pushing changes to a public
1691repository>>", below.
1692
1693Otherwise, the following sections explain how to export your newly
1694created public repository:
1695
1696[[exporting-via-http]]
1697Exporting a git repository via http
b684f830 1698-----------------------------------
d19fbc3c
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1699
1700The git protocol gives better performance and reliability, but on a
1701host with a web server set up, http exports may be simpler to set up.
1702
1703All you need to do is place the newly created bare git repository in
1704a directory that is exported by the web server, and make some
1705adjustments to give web clients some extra information they need:
1706
1707-------------------------------------------------
1708$ mv proj.git /home/you/public_html/proj.git
1709$ cd proj.git
1710$ git update-server-info
1711$ chmod a+x hooks/post-update
1712-------------------------------------------------
1713
1714(For an explanation of the last two lines, see
1715gitlink:git-update-server-info[1], and the documentation
1716link:hooks.txt[Hooks used by git].)
1717
1718Advertise the url of proj.git. Anybody else should then be able to
1719clone or pull from that url, for example with a commandline like:
1720
1721-------------------------------------------------
1722$ git clone http://yourserver.com/~you/proj.git
1723-------------------------------------------------
1724
1725(See also
1726link:howto/setup-git-server-over-http.txt[setup-git-server-over-http]
1727for a slightly more sophisticated setup using WebDAV which also
1728allows pushing over http.)
1729
1730[[exporting-via-git]]
1731Exporting a git repository via the git protocol
b684f830 1732-----------------------------------------------
d19fbc3c
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1733
1734This is the preferred method.
1735
1736For now, we refer you to the gitlink:git-daemon[1] man page for
1737instructions. (See especially the examples section.)
1738
1739[[pushing-changes-to-a-public-repository]]
1740Pushing changes to a public repository
b684f830 1741--------------------------------------
d19fbc3c
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1742
1743Note that the two techniques outline above (exporting via
1744<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
1745maintainers to fetch your latest changes, but they do not allow write
1746access, which you will need to update the public repository with the
1747latest changes created in your private repository.
1748
1749The simplest way to do this is using gitlink:git-push[1] and ssh; to
1750update the remote branch named "master" with the latest state of your
1751branch named "master", run
1752
1753-------------------------------------------------
1754$ git push ssh://yourserver.com/~you/proj.git master:master
1755-------------------------------------------------
1756
1757or just
1758
1759-------------------------------------------------
1760$ git push ssh://yourserver.com/~you/proj.git master
1761-------------------------------------------------
1762
1763As with git-fetch, git-push will complain if this does not result in
1764a <<fast-forwards,fast forward>>. Normally this is a sign of
1765something wrong. However, if you are sure you know what you're
1766doing, you may force git-push to perform the update anyway by
1767proceeding the branch name by a plus sign:
1768
1769-------------------------------------------------
1770$ git push ssh://yourserver.com/~you/proj.git +master
1771-------------------------------------------------
1772
1773As with git-fetch, you may also set up configuration options to
1774save typing; so, for example, after
1775
1776-------------------------------------------------
1777$ cat >.git/config <<EOF
1778[remote "public-repo"]
1779 url = ssh://yourserver.com/~you/proj.git
1780EOF
1781-------------------------------------------------
1782
1783you should be able to perform the above push with just
1784
1785-------------------------------------------------
1786$ git push public-repo master
1787-------------------------------------------------
1788
1789See the explanations of the remote.<name>.url, branch.<name>.remote,
9d13bda3 1790and remote.<name>.push options in gitlink:git-config[1] for
d19fbc3c
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1791details.
1792
1793Setting up a shared repository
b684f830 1794------------------------------
d19fbc3c
BF
1795
1796Another way to collaborate is by using a model similar to that
1797commonly used in CVS, where several developers with special rights
1798all push to and pull from a single shared repository. See
1799link:cvs-migration.txt[git for CVS users] for instructions on how to
1800set this up.
1801
b684f830
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1802Allow web browsing of a repository
1803----------------------------------
d19fbc3c 1804
a8cd1402
BF
1805The gitweb cgi script provides users an easy way to browse your
1806project's files and history without having to install git; see the file
1807gitweb/README in the git source tree for instructions on setting it up.
d19fbc3c 1808
b684f830
BF
1809Examples
1810--------
d19fbc3c 1811
b684f830 1812TODO: topic branches, typical roles as in everyday.txt, ?
d19fbc3c 1813
d19fbc3c 1814
d19fbc3c 1815[[cleaning-up-history]]
4c63ff45
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1816Rewriting history and maintaining patch series
1817==============================================
1818
1819Normally commits are only added to a project, never taken away or
1820replaced. Git is designed with this assumption, and violating it will
1821cause git's merge machinery (for example) to do the wrong thing.
1822
1823However, there is a situation in which it can be useful to violate this
1824assumption.
1825
1826Creating the perfect patch series
1827---------------------------------
1828
1829Suppose you are a contributor to a large project, and you want to add a
1830complicated feature, and to present it to the other developers in a way
1831that makes it easy for them to read your changes, verify that they are
1832correct, and understand why you made each change.
1833
b181d57f
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1834If you present all of your changes as a single patch (or commit), they
1835may find it is too much to digest all at once.
4c63ff45
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1836
1837If you present them with the entire history of your work, complete with
1838mistakes, corrections, and dead ends, they may be overwhelmed.
1839
1840So the ideal is usually to produce a series of patches such that:
1841
1842 1. Each patch can be applied in order.
1843
1844 2. Each patch includes a single logical change, together with a
1845 message explaining the change.
1846
1847 3. No patch introduces a regression: after applying any initial
1848 part of the series, the resulting project still compiles and
1849 works, and has no bugs that it didn't have before.
1850
1851 4. The complete series produces the same end result as your own
1852 (probably much messier!) development process did.
1853
b181d57f
BF
1854We will introduce some tools that can help you do this, explain how to
1855use them, and then explain some of the problems that can arise because
1856you are rewriting history.
4c63ff45
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1857
1858Keeping a patch series up to date using git-rebase
1859--------------------------------------------------
1860
1861Suppose you have a series of commits in a branch "mywork", which
1862originally branched off from "origin".
1863
b181d57f
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1864Suppose you create a branch "mywork" on a remote-tracking branch
1865"origin", and created some commits on top of it:
4c63ff45
BF
1866
1867-------------------------------------------------
1868$ git checkout -b mywork origin
1869$ vi file.txt
1870$ git commit
1871$ vi otherfile.txt
1872$ git commit
1873...
1874-------------------------------------------------
1875
1876You have performed no merges into mywork, so it is just a simple linear
1877sequence of patches on top of "origin":
1878
1879
1880 o--o--o <-- origin
1881 \
1882 o--o--o <-- mywork
1883
1884Some more interesting work has been done in the upstream project, and
1885"origin" has advanced:
1886
1887 o--o--O--o--o--o <-- origin
1888 \
1889 a--b--c <-- mywork
1890
1891At this point, you could use "pull" to merge your changes back in;
1892the result would create a new merge commit, like this:
1893
1894
1895 o--o--O--o--o--o <-- origin
1896 \ \
1897 a--b--c--m <-- mywork
1898
1899However, if you prefer to keep the history in mywork a simple series of
1900commits without any merges, you may instead choose to use
1901gitlink:git-rebase[1]:
1902
1903-------------------------------------------------
1904$ git checkout mywork
1905$ git rebase origin
1906-------------------------------------------------
1907
b181d57f
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1908This will remove each of your commits from mywork, temporarily saving
1909them as patches (in a directory named ".dotest"), update mywork to
1910point at the latest version of origin, then apply each of the saved
1911patches to the new mywork. The result will look like:
4c63ff45
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1912
1913
1914 o--o--O--o--o--o <-- origin
1915 \
1916 a'--b'--c' <-- mywork
1917
b181d57f
BF
1918In the process, it may discover conflicts. In that case it will stop
1919and allow you to fix the conflicts; after fixing conflicts, use "git
1920add" to update the index with those contents, and then, instead of
1921running git-commit, just run
4c63ff45
BF
1922
1923-------------------------------------------------
1924$ git rebase --continue
1925-------------------------------------------------
1926
1927and git will continue applying the rest of the patches.
1928
1929At any point you may use the --abort option to abort this process and
1930return mywork to the state it had before you started the rebase:
1931
1932-------------------------------------------------
1933$ git rebase --abort
1934-------------------------------------------------
1935
1936Reordering or selecting from a patch series
1937-------------------------------------------
1938
b181d57f
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1939Given one existing commit, the gitlink:git-cherry-pick[1] command
1940allows you to apply the change introduced by that commit and create a
1941new commit that records it. So, for example, if "mywork" points to a
1942series of patches on top of "origin", you might do something like:
1943
1944-------------------------------------------------
1945$ git checkout -b mywork-new origin
1946$ gitk origin..mywork &
1947-------------------------------------------------
1948
1949And browse through the list of patches in the mywork branch using gitk,
1950applying them (possibly in a different order) to mywork-new using
1951cherry-pick, and possibly modifying them as you go using commit
1952--amend.
1953
1954Another technique is to use git-format-patch to create a series of
1955patches, then reset the state to before the patches:
4c63ff45 1956
b181d57f
BF
1957-------------------------------------------------
1958$ git format-patch origin
1959$ git reset --hard origin
1960-------------------------------------------------
4c63ff45 1961
b181d57f
BF
1962Then modify, reorder, or eliminate patches as preferred before applying
1963them again with gitlink:git-am[1].
4c63ff45
BF
1964
1965Other tools
1966-----------
1967
b181d57f
BF
1968There are numerous other tools, such as stgit, which exist for the
1969purpose of maintaining a patch series. These are out of the scope of
1970this manual.
4c63ff45
BF
1971
1972Problems with rewriting history
1973-------------------------------
1974
b181d57f
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1975The primary problem with rewriting the history of a branch has to do
1976with merging. Suppose somebody fetches your branch and merges it into
1977their branch, with a result something like this:
1978
1979 o--o--O--o--o--o <-- origin
1980 \ \
1981 t--t--t--m <-- their branch:
1982
1983Then suppose you modify the last three commits:
1984
1985 o--o--o <-- new head of origin
1986 /
1987 o--o--O--o--o--o <-- old head of origin
1988
1989If we examined all this history together in one repository, it will
1990look like:
1991
1992 o--o--o <-- new head of origin
1993 /
1994 o--o--O--o--o--o <-- old head of origin
1995 \ \
1996 t--t--t--m <-- their branch:
1997
1998Git has no way of knowing that the new head is an updated version of
1999the old head; it treats this situation exactly the same as it would if
2000two developers had independently done the work on the old and new heads
2001in parallel. At this point, if someone attempts to merge the new head
2002in to their branch, git will attempt to merge together the two (old and
2003new) lines of development, instead of trying to replace the old by the
2004new. The results are likely to be unexpected.
2005
2006You may still choose to publish branches whose history is rewritten,
2007and it may be useful for others to be able to fetch those branches in
2008order to examine or test them, but they should not attempt to pull such
2009branches into their own work.
2010
2011For true distributed development that supports proper merging,
2012published branches should never be rewritten.
2013
2014Advanced branch management
2015==========================
4c63ff45 2016
b181d57f
BF
2017Fetching individual branches
2018----------------------------
2019
2020Instead of using gitlink:git-remote[1], you can also choose just
2021to update one branch at a time, and to store it locally under an
2022arbitrary name:
2023
2024-------------------------------------------------
2025$ git fetch origin todo:my-todo-work
2026-------------------------------------------------
2027
2028The first argument, "origin", just tells git to fetch from the
2029repository you originally cloned from. The second argument tells git
2030to fetch the branch named "todo" from the remote repository, and to
2031store it locally under the name refs/heads/my-todo-work.
2032
2033You can also fetch branches from other repositories; so
2034
2035-------------------------------------------------
2036$ git fetch git://example.com/proj.git master:example-master
2037-------------------------------------------------
2038
2039will create a new branch named "example-master" and store in it the
2040branch named "master" from the repository at the given URL. If you
2041already have a branch named example-master, it will attempt to
2042"fast-forward" to the commit given by example.com's master branch. So
2043next we explain what a fast-forward is:
2044
2045[[fast-forwards]]
2046Understanding git history: fast-forwards
2047----------------------------------------
2048
2049In the previous example, when updating an existing branch, "git
2050fetch" checks to make sure that the most recent commit on the remote
2051branch is a descendant of the most recent commit on your copy of the
2052branch before updating your copy of the branch to point at the new
2053commit. Git calls this process a "fast forward".
2054
2055A fast forward looks something like this:
2056
2057 o--o--o--o <-- old head of the branch
2058 \
2059 o--o--o <-- new head of the branch
2060
2061
2062In some cases it is possible that the new head will *not* actually be
2063a descendant of the old head. For example, the developer may have
2064realized she made a serious mistake, and decided to backtrack,
2065resulting in a situation like:
2066
2067 o--o--o--o--a--b <-- old head of the branch
2068 \
2069 o--o--o <-- new head of the branch
2070
2071
2072
2073In this case, "git fetch" will fail, and print out a warning.
2074
2075In that case, you can still force git to update to the new head, as
2076described in the following section. However, note that in the
2077situation above this may mean losing the commits labeled "a" and "b",
2078unless you've already created a reference of your own pointing to
2079them.
2080
2081Forcing git fetch to do non-fast-forward updates
2082------------------------------------------------
2083
2084If git fetch fails because the new head of a branch is not a
2085descendant of the old head, you may force the update with:
2086
2087-------------------------------------------------
2088$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
2089-------------------------------------------------
2090
2091Note the addition of the "+" sign. Be aware that commits which the
2092old version of example/master pointed at may be lost, as we saw in
2093the previous section.
2094
2095Configuring remote branches
2096---------------------------
2097
2098We saw above that "origin" is just a shortcut to refer to the
2099repository which you originally cloned from. This information is
2100stored in git configuration variables, which you can see using
9d13bda3 2101gitlink:git-config[1]:
b181d57f
BF
2102
2103-------------------------------------------------
9d13bda3 2104$ git config -l
b181d57f
BF
2105core.repositoryformatversion=0
2106core.filemode=true
2107core.logallrefupdates=true
2108remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
2109remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
2110branch.master.remote=origin
2111branch.master.merge=refs/heads/master
2112-------------------------------------------------
2113
2114If there are other repositories that you also use frequently, you can
2115create similar configuration options to save typing; for example,
2116after
2117
2118-------------------------------------------------
9d13bda3 2119$ git config remote.example.url git://example.com/proj.git
b181d57f
BF
2120-------------------------------------------------
2121
2122then the following two commands will do the same thing:
2123
2124-------------------------------------------------
2125$ git fetch git://example.com/proj.git master:refs/remotes/example/master
2126$ git fetch example master:refs/remotes/example/master
2127-------------------------------------------------
2128
2129Even better, if you add one more option:
2130
2131-------------------------------------------------
9d13bda3 2132$ git config remote.example.fetch master:refs/remotes/example/master
b181d57f
BF
2133-------------------------------------------------
2134
2135then the following commands will all do the same thing:
2136
2137-------------------------------------------------
2138$ git fetch git://example.com/proj.git master:ref/remotes/example/master
2139$ git fetch example master:ref/remotes/example/master
2140$ git fetch example example/master
2141$ git fetch example
2142-------------------------------------------------
2143
2144You can also add a "+" to force the update each time:
2145
2146-------------------------------------------------
9d13bda3 2147$ git config remote.example.fetch +master:ref/remotes/example/master
b181d57f
BF
2148-------------------------------------------------
2149
2150Don't do this unless you're sure you won't mind "git fetch" possibly
2151throwing away commits on mybranch.
2152
2153Also note that all of the above configuration can be performed by
2154directly editing the file .git/config instead of using
9d13bda3 2155gitlink:git-config[1].
b181d57f 2156
9d13bda3 2157See gitlink:git-config[1] for more details on the configuration
b181d57f 2158options mentioned above.
d19fbc3c 2159
d19fbc3c
BF
2160
2161Git internals
2162=============
2163
b181d57f
BF
2164There are two object abstractions: the "object database", and the
2165"current directory cache" aka "index".
2166
2167The Object Database
2168-------------------
2169
2170The object database is literally just a content-addressable collection
2171of objects. All objects are named by their content, which is
2172approximated by the SHA1 hash of the object itself. Objects may refer
2173to other objects (by referencing their SHA1 hash), and so you can
2174build up a hierarchy of objects.
2175
2176All objects have a statically determined "type" aka "tag", which is
2177determined at object creation time, and which identifies the format of
2178the object (i.e. how it is used, and how it can refer to other
2179objects). There are currently four different object types: "blob",
2180"tree", "commit" and "tag".
2181
2182A "blob" object cannot refer to any other object, and is, like the type
2183implies, a pure storage object containing some user data. It is used to
2184actually store the file data, i.e. a blob object is associated with some
2185particular version of some file.
2186
2187A "tree" object is an object that ties one or more "blob" objects into a
2188directory structure. In addition, a tree object can refer to other tree
2189objects, thus creating a directory hierarchy.
2190
2191A "commit" object ties such directory hierarchies together into
2192a DAG of revisions - each "commit" is associated with exactly one tree
2193(the directory hierarchy at the time of the commit). In addition, a
2194"commit" refers to one or more "parent" commit objects that describe the
2195history of how we arrived at that directory hierarchy.
2196
2197As a special case, a commit object with no parents is called the "root"
2198object, and is the point of an initial project commit. Each project
2199must have at least one root, and while you can tie several different
2200root objects together into one project by creating a commit object which
2201has two or more separate roots as its ultimate parents, that's probably
2202just going to confuse people. So aim for the notion of "one root object
2203per project", even if git itself does not enforce that.
2204
2205A "tag" object symbolically identifies and can be used to sign other
2206objects. It contains the identifier and type of another object, a
2207symbolic name (of course!) and, optionally, a signature.
2208
2209Regardless of object type, all objects share the following
2210characteristics: they are all deflated with zlib, and have a header
2211that not only specifies their type, but also provides size information
2212about the data in the object. It's worth noting that the SHA1 hash
2213that is used to name the object is the hash of the original data
2214plus this header, so `sha1sum` 'file' does not match the object name
2215for 'file'.
2216(Historical note: in the dawn of the age of git the hash
2217was the sha1 of the 'compressed' object.)
2218
2219As a result, the general consistency of an object can always be tested
2220independently of the contents or the type of the object: all objects can
2221be validated by verifying that (a) their hashes match the content of the
2222file and (b) the object successfully inflates to a stream of bytes that
2223forms a sequence of <ascii type without space> + <space> + <ascii decimal
2224size> + <byte\0> + <binary object data>.
2225
2226The structured objects can further have their structure and
2227connectivity to other objects verified. This is generally done with
04e50e94 2228the `git-fsck` program, which generates a full dependency graph
b181d57f
BF
2229of all objects, and verifies their internal consistency (in addition
2230to just verifying their superficial consistency through the hash).
2231
2232The object types in some more detail:
2233
2234Blob Object
2235-----------
2236
2237A "blob" object is nothing but a binary blob of data, and doesn't
2238refer to anything else. There is no signature or any other
2239verification of the data, so while the object is consistent (it 'is'
2240indexed by its sha1 hash, so the data itself is certainly correct), it
2241has absolutely no other attributes. No name associations, no
2242permissions. It is purely a blob of data (i.e. normally "file
2243contents").
2244
2245In particular, since the blob is entirely defined by its data, if two
2246files in a directory tree (or in multiple different versions of the
2247repository) have the same contents, they will share the same blob
2248object. The object is totally independent of its location in the
2249directory tree, and renaming a file does not change the object that
2250file is associated with in any way.
2251
2252A blob is typically created when gitlink:git-update-index[1]
2253is run, and its data can be accessed by gitlink:git-cat-file[1].
2254
2255Tree Object
2256-----------
2257
2258The next hierarchical object type is the "tree" object. A tree object
2259is a list of mode/name/blob data, sorted by name. Alternatively, the
2260mode data may specify a directory mode, in which case instead of
2261naming a blob, that name is associated with another TREE object.
2262
2263Like the "blob" object, a tree object is uniquely determined by the
2264set contents, and so two separate but identical trees will always
2265share the exact same object. This is true at all levels, i.e. it's
2266true for a "leaf" tree (which does not refer to any other trees, only
2267blobs) as well as for a whole subdirectory.
2268
2269For that reason a "tree" object is just a pure data abstraction: it
2270has no history, no signatures, no verification of validity, except
2271that since the contents are again protected by the hash itself, we can
2272trust that the tree is immutable and its contents never change.
2273
2274So you can trust the contents of a tree to be valid, the same way you
2275can trust the contents of a blob, but you don't know where those
2276contents 'came' from.
2277
2278Side note on trees: since a "tree" object is a sorted list of
2279"filename+content", you can create a diff between two trees without
2280actually having to unpack two trees. Just ignore all common parts,
2281and your diff will look right. In other words, you can effectively
2282(and efficiently) tell the difference between any two random trees by
2283O(n) where "n" is the size of the difference, rather than the size of
2284the tree.
2285
2286Side note 2 on trees: since the name of a "blob" depends entirely and
2287exclusively on its contents (i.e. there are no names or permissions
2288involved), you can see trivial renames or permission changes by
2289noticing that the blob stayed the same. However, renames with data
2290changes need a smarter "diff" implementation.
2291
2292A tree is created with gitlink:git-write-tree[1] and
2293its data can be accessed by gitlink:git-ls-tree[1].
2294Two trees can be compared with gitlink:git-diff-tree[1].
2295
2296Commit Object
2297-------------
2298
2299The "commit" object is an object that introduces the notion of
2300history into the picture. In contrast to the other objects, it
2301doesn't just describe the physical state of a tree, it describes how
2302we got there, and why.
2303
2304A "commit" is defined by the tree-object that it results in, the
2305parent commits (zero, one or more) that led up to that point, and a
2306comment on what happened. Again, a commit is not trusted per se:
2307the contents are well-defined and "safe" due to the cryptographically
2308strong signatures at all levels, but there is no reason to believe
2309that the tree is "good" or that the merge information makes sense.
2310The parents do not have to actually have any relationship with the
2311result, for example.
2312
2313Note on commits: unlike real SCM's, commits do not contain
2314rename information or file mode change information. All of that is
2315implicit in the trees involved (the result tree, and the result trees
2316of the parents), and describing that makes no sense in this idiotic
2317file manager.
2318
2319A commit is created with gitlink:git-commit-tree[1] and
2320its data can be accessed by gitlink:git-cat-file[1].
2321
2322Trust
2323-----
2324
2325An aside on the notion of "trust". Trust is really outside the scope
2326of "git", but it's worth noting a few things. First off, since
2327everything is hashed with SHA1, you 'can' trust that an object is
2328intact and has not been messed with by external sources. So the name
2329of an object uniquely identifies a known state - just not a state that
2330you may want to trust.
2331
2332Furthermore, since the SHA1 signature of a commit refers to the
2333SHA1 signatures of the tree it is associated with and the signatures
2334of the parent, a single named commit specifies uniquely a whole set
2335of history, with full contents. You can't later fake any step of the
2336way once you have the name of a commit.
2337
2338So to introduce some real trust in the system, the only thing you need
2339to do is to digitally sign just 'one' special note, which includes the
2340name of a top-level commit. Your digital signature shows others
2341that you trust that commit, and the immutability of the history of
2342commits tells others that they can trust the whole history.
2343
2344In other words, you can easily validate a whole archive by just
2345sending out a single email that tells the people the name (SHA1 hash)
2346of the top commit, and digitally sign that email using something
2347like GPG/PGP.
2348
2349To assist in this, git also provides the tag object...
2350
2351Tag Object
2352----------
2353
2354Git provides the "tag" object to simplify creating, managing and
2355exchanging symbolic and signed tokens. The "tag" object at its
2356simplest simply symbolically identifies another object by containing
2357the sha1, type and symbolic name.
2358
2359However it can optionally contain additional signature information
2360(which git doesn't care about as long as there's less than 8k of
2361it). This can then be verified externally to git.
2362
2363Note that despite the tag features, "git" itself only handles content
2364integrity; the trust framework (and signature provision and
2365verification) has to come from outside.
2366
2367A tag is created with gitlink:git-mktag[1],
2368its data can be accessed by gitlink:git-cat-file[1],
2369and the signature can be verified by
2370gitlink:git-verify-tag[1].
2371
2372
2373The "index" aka "Current Directory Cache"
2374-----------------------------------------
2375
2376The index is a simple binary file, which contains an efficient
2377representation of a virtual directory content at some random time. It
2378does so by a simple array that associates a set of names, dates,
2379permissions and content (aka "blob") objects together. The cache is
2380always kept ordered by name, and names are unique (with a few very
2381specific rules) at any point in time, but the cache has no long-term
2382meaning, and can be partially updated at any time.
2383
2384In particular, the index certainly does not need to be consistent with
2385the current directory contents (in fact, most operations will depend on
2386different ways to make the index 'not' be consistent with the directory
2387hierarchy), but it has three very important attributes:
2388
2389'(a) it can re-generate the full state it caches (not just the
2390directory structure: it contains pointers to the "blob" objects so
2391that it can regenerate the data too)'
2392
2393As a special case, there is a clear and unambiguous one-way mapping
2394from a current directory cache to a "tree object", which can be
2395efficiently created from just the current directory cache without
2396actually looking at any other data. So a directory cache at any one
2397time uniquely specifies one and only one "tree" object (but has
2398additional data to make it easy to match up that tree object with what
2399has happened in the directory)
2400
2401'(b) it has efficient methods for finding inconsistencies between that
2402cached state ("tree object waiting to be instantiated") and the
2403current state.'
2404
2405'(c) it can additionally efficiently represent information about merge
2406conflicts between different tree objects, allowing each pathname to be
2407associated with sufficient information about the trees involved that
2408you can create a three-way merge between them.'
2409
2410Those are the three ONLY things that the directory cache does. It's a
2411cache, and the normal operation is to re-generate it completely from a
2412known tree object, or update/compare it with a live tree that is being
2413developed. If you blow the directory cache away entirely, you generally
2414haven't lost any information as long as you have the name of the tree
2415that it described.
2416
2417At the same time, the index is at the same time also the
2418staging area for creating new trees, and creating a new tree always
2419involves a controlled modification of the index file. In particular,
2420the index file can have the representation of an intermediate tree that
2421has not yet been instantiated. So the index can be thought of as a
2422write-back cache, which can contain dirty information that has not yet
2423been written back to the backing store.
2424
2425
2426
2427The Workflow
2428------------
2429
2430Generally, all "git" operations work on the index file. Some operations
2431work *purely* on the index file (showing the current state of the
2432index), but most operations move data to and from the index file. Either
2433from the database or from the working directory. Thus there are four
2434main combinations:
2435
2436working directory -> index
2437~~~~~~~~~~~~~~~~~~~~~~~~~~
2438
2439You update the index with information from the working directory with
2440the gitlink:git-update-index[1] command. You
2441generally update the index information by just specifying the filename
2442you want to update, like so:
2443
2444-------------------------------------------------
2445$ git-update-index filename
2446-------------------------------------------------
2447
2448but to avoid common mistakes with filename globbing etc, the command
2449will not normally add totally new entries or remove old entries,
2450i.e. it will normally just update existing cache entries.
2451
2452To tell git that yes, you really do realize that certain files no
2453longer exist, or that new files should be added, you
2454should use the `--remove` and `--add` flags respectively.
2455
2456NOTE! A `--remove` flag does 'not' mean that subsequent filenames will
2457necessarily be removed: if the files still exist in your directory
2458structure, the index will be updated with their new status, not
2459removed. The only thing `--remove` means is that update-cache will be
2460considering a removed file to be a valid thing, and if the file really
2461does not exist any more, it will update the index accordingly.
2462
2463As a special case, you can also do `git-update-index --refresh`, which
2464will refresh the "stat" information of each index to match the current
2465stat information. It will 'not' update the object status itself, and
2466it will only update the fields that are used to quickly test whether
2467an object still matches its old backing store object.
2468
2469index -> object database
2470~~~~~~~~~~~~~~~~~~~~~~~~
2471
2472You write your current index file to a "tree" object with the program
2473
2474-------------------------------------------------
2475$ git-write-tree
2476-------------------------------------------------
2477
2478that doesn't come with any options - it will just write out the
2479current index into the set of tree objects that describe that state,
2480and it will return the name of the resulting top-level tree. You can
2481use that tree to re-generate the index at any time by going in the
2482other direction:
2483
2484object database -> index
2485~~~~~~~~~~~~~~~~~~~~~~~~
2486
2487You read a "tree" file from the object database, and use that to
2488populate (and overwrite - don't do this if your index contains any
2489unsaved state that you might want to restore later!) your current
2490index. Normal operation is just
2491
2492-------------------------------------------------
2493$ git-read-tree <sha1 of tree>
2494-------------------------------------------------
2495
2496and your index file will now be equivalent to the tree that you saved
2497earlier. However, that is only your 'index' file: your working
2498directory contents have not been modified.
2499
2500index -> working directory
2501~~~~~~~~~~~~~~~~~~~~~~~~~~
2502
2503You update your working directory from the index by "checking out"
2504files. This is not a very common operation, since normally you'd just
2505keep your files updated, and rather than write to your working
2506directory, you'd tell the index files about the changes in your
2507working directory (i.e. `git-update-index`).
2508
2509However, if you decide to jump to a new version, or check out somebody
2510else's version, or just restore a previous tree, you'd populate your
2511index file with read-tree, and then you need to check out the result
2512with
2513
2514-------------------------------------------------
2515$ git-checkout-index filename
2516-------------------------------------------------
2517
2518or, if you want to check out all of the index, use `-a`.
2519
2520NOTE! git-checkout-index normally refuses to overwrite old files, so
2521if you have an old version of the tree already checked out, you will
2522need to use the "-f" flag ('before' the "-a" flag or the filename) to
2523'force' the checkout.
2524
2525
2526Finally, there are a few odds and ends which are not purely moving
2527from one representation to the other:
2528
2529Tying it all together
2530~~~~~~~~~~~~~~~~~~~~~
2531
2532To commit a tree you have instantiated with "git-write-tree", you'd
2533create a "commit" object that refers to that tree and the history
2534behind it - most notably the "parent" commits that preceded it in
2535history.
2536
2537Normally a "commit" has one parent: the previous state of the tree
2538before a certain change was made. However, sometimes it can have two
2539or more parent commits, in which case we call it a "merge", due to the
2540fact that such a commit brings together ("merges") two or more
2541previous states represented by other commits.
2542
2543In other words, while a "tree" represents a particular directory state
2544of a working directory, a "commit" represents that state in "time",
2545and explains how we got there.
2546
2547You create a commit object by giving it the tree that describes the
2548state at the time of the commit, and a list of parents:
2549
2550-------------------------------------------------
2551$ git-commit-tree <tree> -p <parent> [-p <parent2> ..]
2552-------------------------------------------------
2553
2554and then giving the reason for the commit on stdin (either through
2555redirection from a pipe or file, or by just typing it at the tty).
2556
2557git-commit-tree will return the name of the object that represents
2558that commit, and you should save it away for later use. Normally,
2559you'd commit a new `HEAD` state, and while git doesn't care where you
2560save the note about that state, in practice we tend to just write the
2561result to the file pointed at by `.git/HEAD`, so that we can always see
2562what the last committed state was.
2563
2564Here is an ASCII art by Jon Loeliger that illustrates how
2565various pieces fit together.
2566
2567------------
2568
2569 commit-tree
2570 commit obj
2571 +----+
2572 | |
2573 | |
2574 V V
2575 +-----------+
2576 | Object DB |
2577 | Backing |
2578 | Store |
2579 +-----------+
2580 ^
2581 write-tree | |
2582 tree obj | |
2583 | | read-tree
2584 | | tree obj
2585 V
2586 +-----------+
2587 | Index |
2588 | "cache" |
2589 +-----------+
2590 update-index ^
2591 blob obj | |
2592 | |
2593 checkout-index -u | | checkout-index
2594 stat | | blob obj
2595 V
2596 +-----------+
2597 | Working |
2598 | Directory |
2599 +-----------+
2600
2601------------
2602
2603
2604Examining the data
2605------------------
2606
2607You can examine the data represented in the object database and the
2608index with various helper tools. For every object, you can use
2609gitlink:git-cat-file[1] to examine details about the
2610object:
2611
2612-------------------------------------------------
2613$ git-cat-file -t <objectname>
2614-------------------------------------------------
2615
2616shows the type of the object, and once you have the type (which is
2617usually implicit in where you find the object), you can use
2618
2619-------------------------------------------------
2620$ git-cat-file blob|tree|commit|tag <objectname>
2621-------------------------------------------------
2622
2623to show its contents. NOTE! Trees have binary content, and as a result
2624there is a special helper for showing that content, called
2625`git-ls-tree`, which turns the binary content into a more easily
2626readable form.
2627
2628It's especially instructive to look at "commit" objects, since those
2629tend to be small and fairly self-explanatory. In particular, if you
2630follow the convention of having the top commit name in `.git/HEAD`,
2631you can do
2632
2633-------------------------------------------------
2634$ git-cat-file commit HEAD
2635-------------------------------------------------
2636
2637to see what the top commit was.
2638
2639Merging multiple trees
d19fbc3c
BF
2640----------------------
2641
b181d57f
BF
2642Git helps you do a three-way merge, which you can expand to n-way by
2643repeating the merge procedure arbitrary times until you finally
2644"commit" the state. The normal situation is that you'd only do one
2645three-way merge (two parents), and commit it, but if you like to, you
2646can do multiple parents in one go.
2647
2648To do a three-way merge, you need the two sets of "commit" objects
2649that you want to merge, use those to find the closest common parent (a
2650third "commit" object), and then use those commit objects to find the
2651state of the directory ("tree" object) at these points.
2652
2653To get the "base" for the merge, you first look up the common parent
2654of two commits with
2655
2656-------------------------------------------------
2657$ git-merge-base <commit1> <commit2>
2658-------------------------------------------------
2659
2660which will return you the commit they are both based on. You should
2661now look up the "tree" objects of those commits, which you can easily
2662do with (for example)
2663
2664-------------------------------------------------
2665$ git-cat-file commit <commitname> | head -1
2666-------------------------------------------------
2667
2668since the tree object information is always the first line in a commit
2669object.
2670
1191ee18
BF
2671Once you know the three trees you are going to merge (the one "original"
2672tree, aka the common case, and the two "result" trees, aka the branches
2673you want to merge), you do a "merge" read into the index. This will
2674complain if it has to throw away your old index contents, so you should
b181d57f 2675make sure that you've committed those - in fact you would normally
1191ee18
BF
2676always do a merge against your last commit (which should thus match what
2677you have in your current index anyway).
b181d57f
BF
2678
2679To do the merge, do
2680
2681-------------------------------------------------
2682$ git-read-tree -m -u <origtree> <yourtree> <targettree>
2683-------------------------------------------------
2684
2685which will do all trivial merge operations for you directly in the
2686index file, and you can just write the result out with
2687`git-write-tree`.
2688
2689
2690Merging multiple trees, continued
2691---------------------------------
2692
2693Sadly, many merges aren't trivial. If there are files that have
2694been added.moved or removed, or if both branches have modified the
2695same file, you will be left with an index tree that contains "merge
2696entries" in it. Such an index tree can 'NOT' be written out to a tree
2697object, and you will have to resolve any such merge clashes using
2698other tools before you can write out the result.
2699
2700You can examine such index state with `git-ls-files --unmerged`
2701command. An example:
2702
2703------------------------------------------------
2704$ git-read-tree -m $orig HEAD $target
2705$ git-ls-files --unmerged
2706100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
2707100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
2708100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c
2709------------------------------------------------
2710
2711Each line of the `git-ls-files --unmerged` output begins with
2712the blob mode bits, blob SHA1, 'stage number', and the
2713filename. The 'stage number' is git's way to say which tree it
2714came from: stage 1 corresponds to `$orig` tree, stage 2 `HEAD`
2715tree, and stage3 `$target` tree.
2716
2717Earlier we said that trivial merges are done inside
2718`git-read-tree -m`. For example, if the file did not change
2719from `$orig` to `HEAD` nor `$target`, or if the file changed
2720from `$orig` to `HEAD` and `$orig` to `$target` the same way,
2721obviously the final outcome is what is in `HEAD`. What the
2722above example shows is that file `hello.c` was changed from
2723`$orig` to `HEAD` and `$orig` to `$target` in a different way.
2724You could resolve this by running your favorite 3-way merge
2725program, e.g. `diff3` or `merge`, on the blob objects from
2726these three stages yourself, like this:
2727
2728------------------------------------------------
2729$ git-cat-file blob 263414f... >hello.c~1
2730$ git-cat-file blob 06fa6a2... >hello.c~2
2731$ git-cat-file blob cc44c73... >hello.c~3
2732$ merge hello.c~2 hello.c~1 hello.c~3
2733------------------------------------------------
2734
2735This would leave the merge result in `hello.c~2` file, along
2736with conflict markers if there are conflicts. After verifying
2737the merge result makes sense, you can tell git what the final
2738merge result for this file is by:
2739
2740-------------------------------------------------
2741$ mv -f hello.c~2 hello.c
2742$ git-update-index hello.c
2743-------------------------------------------------
2744
2745When a path is in unmerged state, running `git-update-index` for
2746that path tells git to mark the path resolved.
2747
2748The above is the description of a git merge at the lowest level,
2749to help you understand what conceptually happens under the hood.
2750In practice, nobody, not even git itself, uses three `git-cat-file`
2751for this. There is `git-merge-index` program that extracts the
2752stages to temporary files and calls a "merge" script on it:
2753
2754-------------------------------------------------
2755$ git-merge-index git-merge-one-file hello.c
2756-------------------------------------------------
2757
2758and that is what higher level `git resolve` is implemented with.
2759
2760How git stores objects efficiently: pack files
2761----------------------------------------------
2762
2763We've seen how git stores each object in a file named after the
2764object's SHA1 hash.
2765
2766Unfortunately this system becomes inefficient once a project has a
2767lot of objects. Try this on an old project:
2768
2769------------------------------------------------
2770$ git count-objects
27716930 objects, 47620 kilobytes
2772------------------------------------------------
2773
2774The first number is the number of objects which are kept in
2775individual files. The second is the amount of space taken up by
2776those "loose" objects.
2777
2778You can save space and make git faster by moving these loose objects in
2779to a "pack file", which stores a group of objects in an efficient
2780compressed format; the details of how pack files are formatted can be
2781found in link:technical/pack-format.txt[technical/pack-format.txt].
2782
2783To put the loose objects into a pack, just run git repack:
2784
2785------------------------------------------------
2786$ git repack
2787Generating pack...
2788Done counting 6020 objects.
2789Deltifying 6020 objects.
2790 100% (6020/6020) done
2791Writing 6020 objects.
2792 100% (6020/6020) done
2793Total 6020, written 6020 (delta 4070), reused 0 (delta 0)
2794Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.
2795------------------------------------------------
2796
2797You can then run
2798
2799------------------------------------------------
2800$ git prune
2801------------------------------------------------
2802
2803to remove any of the "loose" objects that are now contained in the
2804pack. This will also remove any unreferenced objects (which may be
2805created when, for example, you use "git reset" to remove a commit).
2806You can verify that the loose objects are gone by looking at the
2807.git/objects directory or by running
2808
2809------------------------------------------------
2810$ git count-objects
28110 objects, 0 kilobytes
2812------------------------------------------------
2813
2814Although the object files are gone, any commands that refer to those
2815objects will work exactly as they did before.
2816
2817The gitlink:git-gc[1] command performs packing, pruning, and more for
2818you, so is normally the only high-level command you need.
d19fbc3c 2819
21dcb3b7
BF
2820[[dangling-objects]]
2821Dangling objects
61b41790 2822----------------
21dcb3b7 2823
04e50e94 2824The gitlink:git-fsck[1] command will sometimes complain about dangling
21dcb3b7
BF
2825objects. They are not a problem.
2826
1191ee18
BF
2827The most common cause of dangling objects is that you've rebased a
2828branch, or you have pulled from somebody else who rebased a branch--see
2829<<cleaning-up-history>>. In that case, the old head of the original
2830branch still exists, as does obviously everything it pointed to. The
2831branch pointer itself just doesn't, since you replaced it with another
2832one.
2833
2834There are also other situations too that cause dangling objects. For
2835example, a "dangling blob" may arise because you did a "git add" of a
2836file, but then, before you actually committed it and made it part of the
2837bigger picture, you changed something else in that file and committed
2838that *updated* thing - the old state that you added originally ends up
2839not being pointed to by any commit or tree, so it's now a dangling blob
2840object.
2841
2842Similarly, when the "recursive" merge strategy runs, and finds that
2843there are criss-cross merges and thus more than one merge base (which is
2844fairly unusual, but it does happen), it will generate one temporary
2845midway tree (or possibly even more, if you had lots of criss-crossing
2846merges and more than two merge bases) as a temporary internal merge
2847base, and again, those are real objects, but the end result will not end
2848up pointing to them, so they end up "dangling" in your repository.
2849
2850Generally, dangling objects aren't anything to worry about. They can
2851even be very useful: if you screw something up, the dangling objects can
2852be how you recover your old tree (say, you did a rebase, and realized
2853that you really didn't want to - you can look at what dangling objects
2854you have, and decide to reset your head to some old dangling state).
21dcb3b7 2855
559e4d7a
BF
2856For commits, the most useful thing to do with dangling objects tends to
2857be to do a simple
21dcb3b7
BF
2858
2859------------------------------------------------
2860$ gitk <dangling-commit-sha-goes-here> --not --all
2861------------------------------------------------
2862
1191ee18
BF
2863For blobs and trees, you can't do the same, but you can examine them.
2864You can just do
21dcb3b7
BF
2865
2866------------------------------------------------
2867$ git show <dangling-blob/tree-sha-goes-here>
2868------------------------------------------------
2869
1191ee18
BF
2870to show what the contents of the blob were (or, for a tree, basically
2871what the "ls" for that directory was), and that may give you some idea
2872of what the operation was that left that dangling object.
21dcb3b7 2873
1191ee18
BF
2874Usually, dangling blobs and trees aren't very interesting. They're
2875almost always the result of either being a half-way mergebase (the blob
2876will often even have the conflict markers from a merge in it, if you
2877have had conflicting merges that you fixed up by hand), or simply
2878because you interrupted a "git fetch" with ^C or something like that,
2879leaving _some_ of the new objects in the object database, but just
2880dangling and useless.
21dcb3b7
BF
2881
2882Anyway, once you are sure that you're not interested in any dangling
2883state, you can just prune all unreachable objects:
2884
2885------------------------------------------------
2886$ git prune
2887------------------------------------------------
2888
1191ee18
BF
2889and they'll be gone. But you should only run "git prune" on a quiescent
2890repository - it's kind of like doing a filesystem fsck recovery: you
2891don't want to do that while the filesystem is mounted.
21dcb3b7 2892
04e50e94
BF
2893(The same is true of "git-fsck" itself, btw - but since
2894git-fsck never actually *changes* the repository, it just reports
2895on what it found, git-fsck itself is never "dangerous" to run.
21dcb3b7
BF
2896Running it while somebody is actually changing the repository can cause
2897confusing and scary messages, but it won't actually do anything bad. In
2898contrast, running "git prune" while somebody is actively changing the
2899repository is a *BAD* idea).
2900
d19fbc3c
BF
2901Glossary of git terms
2902=====================
2903
2904include::glossary.txt[]
2905
6bd9b682
BF
2906Notes and todo list for this manual
2907===================================
2908
2909This is a work in progress.
2910
2911The basic requirements:
2f99710c
BF
2912 - It must be readable in order, from beginning to end, by
2913 someone intelligent with a basic grasp of the unix
2914 commandline, but without any special knowledge of git. If
2915 necessary, any other prerequisites should be specifically
2916 mentioned as they arise.
2917 - Whenever possible, section headings should clearly describe
2918 the task they explain how to do, in language that requires
2919 no more knowledge than necessary: for example, "importing
2920 patches into a project" rather than "the git-am command"
6bd9b682 2921
d5cd5de4
BF
2922Think about how to create a clear chapter dependency graph that will
2923allow people to get to important topics without necessarily reading
2924everything in between.
d19fbc3c 2925
aacd404e
MC
2926Say something about .gitignore.
2927
d19fbc3c
BF
2928Scan Documentation/ for other stuff left out; in particular:
2929 howto's
d19fbc3c
BF
2930 some of technical/?
2931 hooks
0b375ab0 2932 list of commands in gitlink:git[1]
d19fbc3c
BF
2933
2934Scan email archives for other stuff left out
2935
2936Scan man pages to see if any assume more background than this manual
2937provides.
2938
2f99710c 2939Simplify beginning by suggesting disconnected head instead of
b181d57f 2940temporary branch creation?
d19fbc3c
BF
2941
2942Explain how to refer to file stages in the "how to resolve a merge"
e9c0390a 2943section: diff -1, -2, -3, --ours, --theirs :1:/path notation. The
2f99710c 2944"git ls-files --unmerged --stage" thing is sorta useful too,
b181d57f 2945actually. And note gitk --merge.
e9c0390a 2946
2f99710c
BF
2947Add more good examples. Entire sections of just cookbook examples
2948might be a good idea; maybe make an "advanced examples" section a
2949standard end-of-chapter section?
d19fbc3c
BF
2950
2951Include cross-references to the glossary, where appropriate.
2952
9a241220
BF
2953Document shallow clones? See draft 1.5.0 release notes for some
2954documentation.
2955
3dff5379 2956Add a section on working with other version control systems, including
9a241220
BF
2957CVS, Subversion, and just imports of series of release tarballs.
2958
a8cd1402 2959More details on gitweb?
0b375ab0
BF
2960
2961Write a chapter on using plumbing and writing scripts.