1GITTUTORIAL(7) Git Manual GITTUTORIAL(7)
2
6 gittutorial - A tutorial introduction to git (for version 1.5.1 or
7 newer)
8
10 git *
11
13 This tutorial explains how to import a new project into git, make
14 changes to it, and share changes with other developers.
15 If you are instead primarily interested in using git to fetch a
17 project, for example, to test the latest version, you may prefer to
18 start with the first two chapters of The Git User’s Manual[1].
19 First, note that you can get documentation for a command such as git
21 log --graph with:
22 $ man git-log
24 or:
27 $ git help log
29 With the latter, you can use the manual viewer of your choice; see git-
32 help(1) for more information.
33 It is a good idea to introduce yourself to git with your name and
35 public email address before doing any operation. The easiest way to do
36 so is:
37 $ git config --global user.name "Your Name Comes Here"
39 $ git config --global user.email you@yourdomain.example.com
40
43 Assume you have a tarball project.tar.gz with your initial work. You
44 can place it under git revision control as follows.
45 $ tar xzf project.tar.gz
47 $ cd project
48 $ git init
49 Git will reply
52 Initialized empty Git repository in .git/
54 You’ve now initialized the working directory—you may notice a new
57 directory created, named ".git".
58 Next, tell git to take a snapshot of the contents of all files under
60 the current directory (note the .), with git add:
61 $ git add .
63 This snapshot is now stored in a temporary staging area which git calls
66 the "index". You can permanently store the contents of the index in the
67 repository with git commit:
68 $ git commit
70 This will prompt you for a commit message. You’ve now stored the first
73 version of your project in git.
74
76 Modify some files, then add their updated contents to the index:
77 $ git add file1 file2 file3
79 You are now ready to commit. You can see what is about to be committed
82 using git diff with the --cached option:
83 $ git diff --cached
85 (Without --cached, git diff will show you any changes that you’ve made
88 but not yet added to the index.) You can also get a brief summary of
89 the situation with git status:
90 $ git status
92 # On branch master
93 # Changes to be committed:
94 # (use "git reset HEAD <file>..." to unstage)
95 #
96 # modified: file1
97 # modified: file2
98 # modified: file3
99 #
100 If you need to make any further adjustments, do so now, and then add
103 any newly modified content to the index. Finally, commit your changes
104 with:
105 $ git commit
107 This will again prompt you for a message describing the change, and
110 then record a new version of the project.
111 Alternatively, instead of running git add beforehand, you can use
113 $ git commit -a
115 which will automatically notice any modified (but not new) files, add
118 them to the index, and commit, all in one step.
119 A note on commit messages: Though not required, it’s a good idea to
121 begin the commit message with a single short (less than 50 character)
122 line summarizing the change, followed by a blank line and then a more
123 thorough description. Tools that turn commits into email, for example,
124 use the first line on the Subject: line and the rest of the commit in
125 the body.
126
128 Many revision control systems provide an add command that tells the
129 system to start tracking changes to a new file. Git’s add command does
130 something simpler and more powerful: git add is used both for new and
131 newly modified files, and in both cases it takes a snapshot of the
132 given files and stages that content in the index, ready for inclusion
133 in the next commit.
134
136 At any point you can view the history of your changes using
137 $ git log
139 If you also want to see complete diffs at each step, use
142 $ git log -p
144 Often the overview of the change is useful to get a feel of each step
147 $ git log --stat --summary
149
152 A single git repository can maintain multiple branches of development.
153 To create a new branch named "experimental", use
154 $ git branch experimental
156 If you now run
159 $ git branch
161 you’ll get a list of all existing branches:
164 experimental
166 * master
167 The "experimental" branch is the one you just created, and the "master"
170 branch is a default branch that was created for you automatically. The
171 asterisk marks the branch you are currently on; type
172 $ git checkout experimental
174 to switch to the experimental branch. Now edit a file, commit the
177 change, and switch back to the master branch:
178 (edit file)
180 $ git commit -a
181 $ git checkout master
182 Check that the change you made is no longer visible, since it was made
185 on the experimental branch and you’re back on the master branch.
186 You can make a different change on the master branch:
188 (edit file)
190 $ git commit -a
191 at this point the two branches have diverged, with different changes
194 made in each. To merge the changes made in experimental into master,
195 run
196 $ git merge experimental
198 If the changes don’t conflict, you’re done. If there are conflicts,
201 markers will be left in the problematic files showing the conflict;
202 $ git diff
204 will show this. Once you’ve edited the files to resolve the conflicts,
207 $ git commit -a
209 will commit the result of the merge. Finally,
212 $ gitk
214 will show a nice graphical representation of the resulting history.
217 At this point you could delete the experimental branch with
219 $ git branch -d experimental
221 This command ensures that the changes in the experimental branch are
224 already in the current branch.
225 If you develop on a branch crazy-idea, then regret it, you can always
227 delete the branch with
228 $ git branch -D crazy-idea
230 Branches are cheap and easy, so this is a good way to try something
233 out.
234
236 Suppose that Alice has started a new project with a git repository in
237 /home/alice/project, and that Bob, who has a home directory on the same
238 machine, wants to contribute.
239 Bob begins with:
241 bob$ git clone /home/alice/project myrepo
243 This creates a new directory "myrepo" containing a clone of Alice’s
246 repository. The clone is on an equal footing with the original project,
247 possessing its own copy of the original project’s history.
248 Bob then makes some changes and commits them:
250 (edit files)
252 bob$ git commit -a
253 (repeat as necessary)
254 When he’s ready, he tells Alice to pull changes from the repository at
257 /home/bob/myrepo. She does this with:
258 alice$ cd /home/alice/project
260 alice$ git pull /home/bob/myrepo master
261 This merges the changes from Bob’s "master" branch into Alice’s current
264 branch. If Alice has made her own changes in the meantime, then she may
265 need to manually fix any conflicts.
266 The "pull" command thus performs two operations: it fetches changes
268 from a remote branch, then merges them into the current branch.
269 Note that in general, Alice would want her local changes committed
271 before initiating this "pull". If Bob’s work conflicts with what Alice
272 did since their histories forked, Alice will use her working tree and
273 the index to resolve conflicts, and existing local changes will
274 interfere with the conflict resolution process (git will still perform
275 the fetch but will refuse to merge --- Alice will have to get rid of
276 her local changes in some way and pull again when this happens).
277 Alice can peek at what Bob did without merging first, using the "fetch"
279 command; this allows Alice to inspect what Bob did, using a special
280 symbol "FETCH_HEAD", in order to determine if he has anything worth
281 pulling, like this:
282 alice$ git fetch /home/bob/myrepo master
284 alice$ git log -p HEAD..FETCH_HEAD
285 This operation is safe even if Alice has uncommitted local changes. The
288 range notation "HEAD..FETCH_HEAD" means "show everything that is
289 reachable from the FETCH_HEAD but exclude anything that is reachable
290 from HEAD". Alice already knows everything that leads to her current
291 state (HEAD), and reviews what Bob has in his state (FETCH_HEAD) that
292 she has not seen with this command.
293 If Alice wants to visualize what Bob did since their histories forked
295 she can issue the following command:
296 $ gitk HEAD..FETCH_HEAD
298 This uses the same two-dot range notation we saw earlier with git log.
301 Alice may want to view what both of them did since they forked. She can
303 use three-dot form instead of the two-dot form:
304 $ gitk HEAD...FETCH_HEAD
306 This means "show everything that is reachable from either one, but
309 exclude anything that is reachable from both of them".
310 Please note that these range notation can be used with both gitk and
312 "git log".
313 After inspecting what Bob did, if there is nothing urgent, Alice may
315 decide to continue working without pulling from Bob. If Bob’s history
316 does have something Alice would immediately need, Alice may choose to
317 stash her work-in-progress first, do a "pull", and then finally unstash
318 her work-in-progress on top of the resulting history.
319 When you are working in a small closely knit group, it is not unusual
321 to interact with the same repository over and over again. By defining
322 remote repository shorthand, you can make it easier:
323 alice$ git remote add bob /home/bob/myrepo
325 With this, Alice can perform the first part of the "pull" operation
328 alone using the git fetch command without merging them with her own
329 branch, using:
330 alice$ git fetch bob
332 Unlike the longhand form, when Alice fetches from Bob using a remote
335 repository shorthand set up with git remote, what was fetched is stored
336 in a remote tracking branch, in this case bob/master. So after this:
337 alice$ git log -p master..bob/master
339 shows a list of all the changes that Bob made since he branched from
342 Alice’s master branch.
343 After examining those changes, Alice could merge the changes into her
345 master branch:
346 alice$ git merge bob/master
348 This merge can also be done by pulling from her own remote tracking
351 branch, like this:
352 alice$ git pull . remotes/bob/master
354 Note that git pull always merges into the current branch, regardless of
357 what else is given on the command line.
358 Later, Bob can update his repo with Alice’s latest changes using
360 bob$ git pull
362 Note that he doesn’t need to give the path to Alice’s repository; when
365 Bob cloned Alice’s repository, git stored the location of her
366 repository in the repository configuration, and that location is used
367 for pulls:
368 bob$ git config --get remote.origin.url
370 /home/alice/project
371 (The complete configuration created by git clone is visible using git
374 config -l, and the git-config(1) man page explains the meaning of each
375 option.)
376 Git also keeps a pristine copy of Alice’s master branch under the name
378 "origin/master":
379 bob$ git branch -r
381 origin/master
382 If Bob later decides to work from a different host, he can still
385 perform clones and pulls using the ssh protocol:
386 bob$ git clone alice.org:/home/alice/project myrepo
388 Alternatively, git has a native protocol, or can use rsync or http; see
391 git-pull(1) for details.
392 Git can also be used in a CVS-like mode, with a central repository that
394 various users push changes to; see git-push(1) and gitcvs-migration(7).
395
397 Git history is represented as a series of interrelated commits. We have
398 already seen that the git log command can list those commits. Note that
399 first line of each git log entry also gives a name for the commit:
400 $ git log
402 commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
403 Author: Junio C Hamano <junkio@cox.net>
404 Date: Tue May 16 17:18:22 2006 -0700
405 merge-base: Clarify the comments on post processing.
407 We can give this name to git show to see the details about this commit.
410 $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
412 But there are other ways to refer to commits. You can use any initial
415 part of the name that is long enough to uniquely identify the commit:
416 $ git show c82a22c39c # the first few characters of the name are
418 # usually enough
419 $ git show HEAD # the tip of the current branch
420 $ git show experimental # the tip of the "experimental" branch
421 Every commit usually has one "parent" commit which points to the
424 previous state of the project:
425 $ git show HEAD^ # to see the parent of HEAD
427 $ git show HEAD^^ # to see the grandparent of HEAD
428 $ git show HEAD~4 # to see the great-great grandparent of HEAD
429 Note that merge commits may have more than one parent:
432 $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
434 $ git show HEAD^2 # show the second parent of HEAD
435 You can also give commits names of your own; after running
438 $ git tag v2.5 1b2e1d63ff
440 you can refer to 1b2e1d63ff by the name "v2.5". If you intend to share
443 this name with other people (for example, to identify a release
444 version), you should create a "tag" object, and perhaps sign it; see
445 git-tag(1) for details.
446 Any git command that needs to know a commit can take any of these
448 names. For example:
449 $ git diff v2.5 HEAD # compare the current HEAD to v2.5
451 $ git branch stable v2.5 # start a new branch named "stable" based
452 # at v2.5
453 $ git reset --hard HEAD^ # reset your current branch and working
454 # directory to its state at HEAD^
455 Be careful with that last command: in addition to losing any changes in
458 the working directory, it will also remove all later commits from this
459 branch. If this branch is the only branch containing those commits,
460 they will be lost. Also, don’t use git reset on a publicly-visible
461 branch that other developers pull from, as it will force needless
462 merges on other developers to clean up the history. If you need to undo
463 changes that you have pushed, use git revert instead.
464 The git grep command can search for strings in any version of your
466 project, so
467 $ git grep "hello" v2.5
469 searches for all occurrences of "hello" in v2.5.
472 If you leave out the commit name, git grep will search any of the files
474 it manages in your current directory. So
475 $ git grep "hello"
477 is a quick way to search just the files that are tracked by git.
480 Many git commands also take sets of commits, which can be specified in
482 a number of ways. Here are some examples with git log:
483 $ git log v2.5..v2.6 # commits between v2.5 and v2.6
485 $ git log v2.5.. # commits since v2.5
486 $ git log --since="2 weeks ago" # commits from the last 2 weeks
487 $ git log v2.5.. Makefile # commits since v2.5 which modify
488 # Makefile
489 You can also give git log a "range" of commits where the first is not
492 necessarily an ancestor of the second; for example, if the tips of the
493 branches "stable" and "master" diverged from a common commit some time
494 ago, then
495 $ git log stable..master
497 will list commits made in the master branch but not in the stable
500 branch, while
501 $ git log master..stable
503 will show the list of commits made on the stable branch but not the
506 master branch.
507 The git log command has a weakness: it must present commits in a list.
509 When the history has lines of development that diverged and then merged
510 back together, the order in which git log presents those commits is
511 meaningless.
512 Most projects with multiple contributors (such as the Linux kernel, or
514 git itself) have frequent merges, and gitk does a better job of
515 visualizing their history. For example,
516 $ gitk --since="2 weeks ago" drivers/
518 allows you to browse any commits from the last 2 weeks of commits that
521 modified files under the "drivers" directory. (Note: you can adjust
522 gitk’s fonts by holding down the control key while pressing "-" or
523 "+".)
524 Finally, most commands that take filenames will optionally allow you to
526 precede any filename by a commit, to specify a particular version of
527 the file:
528 $ git diff v2.5:Makefile HEAD:Makefile.in
530 You can also use git show to see any such file:
533 $ git show v2.5:Makefile
535
538 This tutorial should be enough to perform basic distributed revision
539 control for your projects. However, to fully understand the depth and
540 power of git you need to understand two simple ideas on which it is
541 based:
542 · The object database is the rather elegant system used to store the
544 history of your project—files, directories, and commits.
545 · The index file is a cache of the state of a directory tree, used to
547 create commits, check out working directories, and hold the various
548 trees involved in a merge.
549 Part two of this tutorial explains the object database, the index file,
551 and a few other odds and ends that you’ll need to make the most of git.
552 You can find it at gittutorial-2(7).
553 If you don’t want to continue with that right away, a few other
555 digressions that may be interesting at this point are:
556 · git-format-patch(1), git-am(1): These convert series of git
558 commits into emailed patches, and vice versa, useful for projects
559 such as the Linux kernel which rely heavily on emailed patches.
560 · git-bisect(1): When there is a regression in your project, one way
562 to track down the bug is by searching through the history to find
563 the exact commit that’s to blame. Git bisect can help you perform a
564 binary search for that commit. It is smart enough to perform a
565 close-to-optimal search even in the case of complex non-linear
566 history with lots of merged branches.
567 · gitworkflows(7): Gives an overview of recommended workflows.
569 · Everyday GIT with 20 Commands Or So[2]
571 · gitcvs-migration(7): Git for CVS users.
573
575 gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
576 gitglossary(7), git-help(1), gitworkflows(7), Everyday git[2], The Git
577 User’s Manual[1]
578
580 Part of the git(1) suite.
581
583 1. The Git User’s Manual
584 file:///usr/share/doc/git-1.7.1/user-manual.html
585 2. Everyday GIT with 20 Commands Or So
587 file:///usr/share/doc/git-1.7.1/everyday.html
588Git 1.7.1 08/16/2017 GITTUTORIAL(7)