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
14 This tutorial explains how to import a new project into Git, make
15 changes to it, and share changes with other developers.
16 If you are instead primarily interested in using Git to fetch a
18 project, for example, to test the latest version, you may prefer to
19 start with the first two chapters of The Git User’s Manual[1].
20 First, note that you can get documentation for a command such as git
22 log --graph with:
23 $ man git-log
25 or:
28 $ git help log
30 With the latter, you can use the manual viewer of your choice; see git-
33 help(1) for more information.
34 It is a good idea to introduce yourself to Git with your name and
36 public email address before doing any operation. The easiest way to do
37 so is:
38 $ git config --global user.name "Your Name Comes Here"
40 $ git config --global user.email you@yourdomain.example.com
41
44 Assume you have a tarball project.tar.gz with your initial work. You
45 can place it under Git revision control as follows.
46 $ tar xzf project.tar.gz
48 $ cd project
49 $ git init
50 Git will reply
53 Initialized empty Git repository in .git/
55 You’ve now initialized the working directory—you may notice a new
58 directory created, named ".git".
59 Next, tell Git to take a snapshot of the contents of all files under
61 the current directory (note the .), with git add:
62 $ git add .
64 This snapshot is now stored in a temporary staging area which Git calls
67 the "index". You can permanently store the contents of the index in the
68 repository with git commit:
69 $ git commit
71 This will prompt you for a commit message. You’ve now stored the first
74 version of your project in Git.
75
77 Modify some files, then add their updated contents to the index:
78 $ git add file1 file2 file3
80 You are now ready to commit. You can see what is about to be committed
83 using git diff with the --cached option:
84 $ git diff --cached
86 (Without --cached, git diff will show you any changes that you’ve made
89 but not yet added to the index.) You can also get a brief summary of
90 the situation with git status:
91 $ git status
93 # On branch master
94 # Changes to be committed:
95 # (use "git reset HEAD <file>..." to unstage)
96 #
97 # modified: file1
98 # modified: file2
99 # modified: file3
100 #
101 If you need to make any further adjustments, do so now, and then add
104 any newly modified content to the index. Finally, commit your changes
105 with:
106 $ git commit
108 This will again prompt you for a message describing the change, and
111 then record a new version of the project.
112 Alternatively, instead of running git add beforehand, you can use
114 $ git commit -a
116 which will automatically notice any modified (but not new) files, add
119 them to the index, and commit, all in one step.
120 A note on commit messages: Though not required, it’s a good idea to
122 begin the commit message with a single short (less than 50 character)
123 line summarizing the change, followed by a blank line and then a more
124 thorough description. The text up to the first blank line in a commit
125 message is treated as the commit title, and that title is used
126 throughout Git. For example, git-format-patch(1) turns a commit into
127 email, and it uses the title on the Subject line and the rest of the
128 commit in the body.
129
131 Many revision control systems provide an add command that tells the
132 system to start tracking changes to a new file. Git’s add command does
133 something simpler and more powerful: git add is used both for new and
134 newly modified files, and in both cases it takes a snapshot of the
135 given files and stages that content in the index, ready for inclusion
136 in the next commit.
137
139 At any point you can view the history of your changes using
140 $ git log
142 If you also want to see complete diffs at each step, use
145 $ git log -p
147 Often the overview of the change is useful to get a feel of each step
150 $ git log --stat --summary
152
155 A single Git repository can maintain multiple branches of development.
156 To create a new branch named "experimental", use
157 $ git branch experimental
159 If you now run
162 $ git branch
164 you’ll get a list of all existing branches:
167 experimental
169 * master
170 The "experimental" branch is the one you just created, and the "master"
173 branch is a default branch that was created for you automatically. The
174 asterisk marks the branch you are currently on; type
175 $ git checkout experimental
177 to switch to the experimental branch. Now edit a file, commit the
180 change, and switch back to the master branch:
181 (edit file)
183 $ git commit -a
184 $ git checkout master
185 Check that the change you made is no longer visible, since it was made
188 on the experimental branch and you’re back on the master branch.
189 You can make a different change on the master branch:
191 (edit file)
193 $ git commit -a
194 at this point the two branches have diverged, with different changes
197 made in each. To merge the changes made in experimental into master,
198 run
199 $ git merge experimental
201 If the changes don’t conflict, you’re done. If there are conflicts,
204 markers will be left in the problematic files showing the conflict;
205 $ git diff
207 will show this. Once you’ve edited the files to resolve the conflicts,
210 $ git commit -a
212 will commit the result of the merge. Finally,
215 $ gitk
217 will show a nice graphical representation of the resulting history.
220 At this point you could delete the experimental branch with
222 $ git branch -d experimental
224 This command ensures that the changes in the experimental branch are
227 already in the current branch.
228 If you develop on a branch crazy-idea, then regret it, you can always
230 delete the branch with
231 $ git branch -D crazy-idea
233 Branches are cheap and easy, so this is a good way to try something
236 out.
237
239 Suppose that Alice has started a new project with a Git repository in
240 /home/alice/project, and that Bob, who has a home directory on the same
241 machine, wants to contribute.
242 Bob begins with:
244 bob$ git clone /home/alice/project myrepo
246 This creates a new directory "myrepo" containing a clone of Alice’s
249 repository. The clone is on an equal footing with the original project,
250 possessing its own copy of the original project’s history.
251 Bob then makes some changes and commits them:
253 (edit files)
255 bob$ git commit -a
256 (repeat as necessary)
257 When he’s ready, he tells Alice to pull changes from the repository at
260 /home/bob/myrepo. She does this with:
261 alice$ cd /home/alice/project
263 alice$ git pull /home/bob/myrepo master
264 This merges the changes from Bob’s "master" branch into Alice’s current
267 branch. If Alice has made her own changes in the meantime, then she may
268 need to manually fix any conflicts.
269 The "pull" command thus performs two operations: it fetches changes
271 from a remote branch, then merges them into the current branch.
272 Note that in general, Alice would want her local changes committed
274 before initiating this "pull". If Bob’s work conflicts with what Alice
275 did since their histories forked, Alice will use her working tree and
276 the index to resolve conflicts, and existing local changes will
277 interfere with the conflict resolution process (Git will still perform
278 the fetch but will refuse to merge --- Alice will have to get rid of
279 her local changes in some way and pull again when this happens).
280 Alice can peek at what Bob did without merging first, using the "fetch"
282 command; this allows Alice to inspect what Bob did, using a special
283 symbol "FETCH_HEAD", in order to determine if he has anything worth
284 pulling, like this:
285 alice$ git fetch /home/bob/myrepo master
287 alice$ git log -p HEAD..FETCH_HEAD
288 This operation is safe even if Alice has uncommitted local changes. The
291 range notation "HEAD..FETCH_HEAD" means "show everything that is
292 reachable from the FETCH_HEAD but exclude anything that is reachable
293 from HEAD". Alice already knows everything that leads to her current
294 state (HEAD), and reviews what Bob has in his state (FETCH_HEAD) that
295 she has not seen with this command.
296 If Alice wants to visualize what Bob did since their histories forked
298 she can issue the following command:
299 $ gitk HEAD..FETCH_HEAD
301 This uses the same two-dot range notation we saw earlier with git log.
304 Alice may want to view what both of them did since they forked. She can
306 use three-dot form instead of the two-dot form:
307 $ gitk HEAD...FETCH_HEAD
309 This means "show everything that is reachable from either one, but
312 exclude anything that is reachable from both of them".
313 Please note that these range notation can be used with both gitk and
315 "git log".
316 After inspecting what Bob did, if there is nothing urgent, Alice may
318 decide to continue working without pulling from Bob. If Bob’s history
319 does have something Alice would immediately need, Alice may choose to
320 stash her work-in-progress first, do a "pull", and then finally unstash
321 her work-in-progress on top of the resulting history.
322 When you are working in a small closely knit group, it is not unusual
324 to interact with the same repository over and over again. By defining
325 remote repository shorthand, you can make it easier:
326 alice$ git remote add bob /home/bob/myrepo
328 With this, Alice can perform the first part of the "pull" operation
331 alone using the git fetch command without merging them with her own
332 branch, using:
333 alice$ git fetch bob
335 Unlike the longhand form, when Alice fetches from Bob using a remote
338 repository shorthand set up with git remote, what was fetched is stored
339 in a remote-tracking branch, in this case bob/master. So after this:
340 alice$ git log -p master..bob/master
342 shows a list of all the changes that Bob made since he branched from
345 Alice’s master branch.
346 After examining those changes, Alice could merge the changes into her
348 master branch:
349 alice$ git merge bob/master
351 This merge can also be done by pulling from her own remote-tracking
354 branch, like this:
355 alice$ git pull . remotes/bob/master
357 Note that git pull always merges into the current branch, regardless of
360 what else is given on the command line.
361 Later, Bob can update his repo with Alice’s latest changes using
363 bob$ git pull
365 Note that he doesn’t need to give the path to Alice’s repository; when
368 Bob cloned Alice’s repository, Git stored the location of her
369 repository in the repository configuration, and that location is used
370 for pulls:
371 bob$ git config --get remote.origin.url
373 /home/alice/project
374 (The complete configuration created by git clone is visible using git
377 config -l, and the git-config(1) man page explains the meaning of each
378 option.)
379 Git also keeps a pristine copy of Alice’s master branch under the name
381 "origin/master":
382 bob$ git branch -r
384 origin/master
385 If Bob later decides to work from a different host, he can still
388 perform clones and pulls using the ssh protocol:
389 bob$ git clone alice.org:/home/alice/project myrepo
391 Alternatively, Git has a native protocol, or can use rsync or http; see
394 git-pull(1) for details.
395 Git can also be used in a CVS-like mode, with a central repository that
397 various users push changes to; see git-push(1) and gitcvs-migration(7).
398
400 Git history is represented as a series of interrelated commits. We have
401 already seen that the git log command can list those commits. Note that
402 first line of each git log entry also gives a name for the commit:
403 $ git log
405 commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
406 Author: Junio C Hamano <junkio@cox.net>
407 Date: Tue May 16 17:18:22 2006 -0700
408 merge-base: Clarify the comments on post processing.
410 We can give this name to git show to see the details about this commit.
413 $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
415 But there are other ways to refer to commits. You can use any initial
418 part of the name that is long enough to uniquely identify the commit:
419 $ git show c82a22c39c # the first few characters of the name are
421 # usually enough
422 $ git show HEAD # the tip of the current branch
423 $ git show experimental # the tip of the "experimental" branch
424 Every commit usually has one "parent" commit which points to the
427 previous state of the project:
428 $ git show HEAD^ # to see the parent of HEAD
430 $ git show HEAD^^ # to see the grandparent of HEAD
431 $ git show HEAD~4 # to see the great-great grandparent of HEAD
432 Note that merge commits may have more than one parent:
435 $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
437 $ git show HEAD^2 # show the second parent of HEAD
438 You can also give commits names of your own; after running
441 $ git tag v2.5 1b2e1d63ff
443 you can refer to 1b2e1d63ff by the name "v2.5". If you intend to share
446 this name with other people (for example, to identify a release
447 version), you should create a "tag" object, and perhaps sign it; see
448 git-tag(1) for details.
449 Any Git command that needs to know a commit can take any of these
451 names. For example:
452 $ git diff v2.5 HEAD # compare the current HEAD to v2.5
454 $ git branch stable v2.5 # start a new branch named "stable" based
455 # at v2.5
456 $ git reset --hard HEAD^ # reset your current branch and working
457 # directory to its state at HEAD^
458 Be careful with that last command: in addition to losing any changes in
461 the working directory, it will also remove all later commits from this
462 branch. If this branch is the only branch containing those commits,
463 they will be lost. Also, don’t use git reset on a publicly-visible
464 branch that other developers pull from, as it will force needless
465 merges on other developers to clean up the history. If you need to undo
466 changes that you have pushed, use git revert instead.
467 The git grep command can search for strings in any version of your
469 project, so
470 $ git grep "hello" v2.5
472 searches for all occurrences of "hello" in v2.5.
475 If you leave out the commit name, git grep will search any of the files
477 it manages in your current directory. So
478 $ git grep "hello"
480 is a quick way to search just the files that are tracked by Git.
483 Many Git commands also take sets of commits, which can be specified in
485 a number of ways. Here are some examples with git log:
486 $ git log v2.5..v2.6 # commits between v2.5 and v2.6
488 $ git log v2.5.. # commits since v2.5
489 $ git log --since="2 weeks ago" # commits from the last 2 weeks
490 $ git log v2.5.. Makefile # commits since v2.5 which modify
491 # Makefile
492 You can also give git log a "range" of commits where the first is not
495 necessarily an ancestor of the second; for example, if the tips of the
496 branches "stable" and "master" diverged from a common commit some time
497 ago, then
498 $ git log stable..master
500 will list commits made in the master branch but not in the stable
503 branch, while
504 $ git log master..stable
506 will show the list of commits made on the stable branch but not the
509 master branch.
510 The git log command has a weakness: it must present commits in a list.
512 When the history has lines of development that diverged and then merged
513 back together, the order in which git log presents those commits is
514 meaningless.
515 Most projects with multiple contributors (such as the Linux kernel, or
517 Git itself) have frequent merges, and gitk does a better job of
518 visualizing their history. For example,
519 $ gitk --since="2 weeks ago" drivers/
521 allows you to browse any commits from the last 2 weeks of commits that
524 modified files under the "drivers" directory. (Note: you can adjust
525 gitk’s fonts by holding down the control key while pressing "-" or
526 "+".)
527 Finally, most commands that take filenames will optionally allow you to
529 precede any filename by a commit, to specify a particular version of
530 the file:
531 $ git diff v2.5:Makefile HEAD:Makefile.in
533 You can also use git show to see any such file:
536 $ git show v2.5:Makefile
538
541 This tutorial should be enough to perform basic distributed revision
542 control for your projects. However, to fully understand the depth and
543 power of Git you need to understand two simple ideas on which it is
544 based:
545 · The object database is the rather elegant system used to store the
547 history of your project—files, directories, and commits.
548 · The index file is a cache of the state of a directory tree, used to
550 create commits, check out working directories, and hold the various
551 trees involved in a merge.
552 Part two of this tutorial explains the object database, the index file,
554 and a few other odds and ends that you’ll need to make the most of Git.
555 You can find it at gittutorial-2(7).
556 If you don’t want to continue with that right away, a few other
558 digressions that may be interesting at this point are:
559 · git-format-patch(1), git-am(1): These convert series of git commits
561 into emailed patches, and vice versa, useful for projects such as
562 the Linux kernel which rely heavily on emailed patches.
563 · git-bisect(1): When there is a regression in your project, one way
565 to track down the bug is by searching through the history to find
566 the exact commit that’s to blame. Git bisect can help you perform a
567 binary search for that commit. It is smart enough to perform a
568 close-to-optimal search even in the case of complex non-linear
569 history with lots of merged branches.
570 · gitworkflows(7): Gives an overview of recommended workflows.
572 · Everyday Git with 20 Commands Or So[2]
574 · gitcvs-migration(7): Git for CVS users.
576
578 gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
579 gitglossary(7), git-help(1), gitworkflows(7), Everyday Git[2], The Git
580 User’s Manual[1]
581
583 Part of the git(1) suite.
584
586 1. The Git User’s Manual
587 file:///usr/share/doc/git-1.8.3.1/user-manual.html
588 2. Everyday Git with 20 Commands Or So
590 file:///usr/share/doc/git-1.8.3.1/everyday.html
591Git 1.8.3.1 11/19/2018 GITTUTORIAL(7)