1GITTUTORIAL(7) Git Manual GITTUTORIAL(7)
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6 gittutorial - A tutorial introduction to Git
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9 git *
10
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 Your branch is up to date with 'origin/master'.
95 (use "git reset HEAD <file>..." to unstage)
96 modified: file1
98 modified: file2
99 modified: file3
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. The text up to the first blank line in a commit
124 message is treated as the commit title, and that title is used
125 throughout Git. For example, git-format-patch(1) turns a commit into
126 email, and it uses the title on the Subject line and the rest of the
127 commit in the body.
128
130 Many revision control systems provide an add command that tells the
131 system to start tracking changes to a new file. Git’s add command does
132 something simpler and more powerful: git add is used both for new and
133 newly modified files, and in both cases it takes a snapshot of the
134 given files and stages that content in the index, ready for inclusion
135 in the next commit.
136
138 At any point you can view the history of your changes using
139 $ git log
141 If you also want to see complete diffs at each step, use
144 $ git log -p
146 Often the overview of the change is useful to get a feel of each step
149 $ git log --stat --summary
151
154 A single Git repository can maintain multiple branches of development.
155 To create a new branch named "experimental", use
156 $ git branch experimental
158 If you now run
161 $ git branch
163 you’ll get a list of all existing branches:
166 experimental
168 * master
169 The "experimental" branch is the one you just created, and the "master"
172 branch is a default branch that was created for you automatically. The
173 asterisk marks the branch you are currently on; type
174 $ git checkout experimental
176 to switch to the experimental branch. Now edit a file, commit the
179 change, and switch back to the master branch:
180 (edit file)
182 $ git commit -a
183 $ git checkout master
184 Check that the change you made is no longer visible, since it was made
187 on the experimental branch and you’re back on the master branch.
188 You can make a different change on the master branch:
190 (edit file)
192 $ git commit -a
193 at this point the two branches have diverged, with different changes
196 made in each. To merge the changes made in experimental into master,
197 run
198 $ git merge experimental
200 If the changes don’t conflict, you’re done. If there are conflicts,
203 markers will be left in the problematic files showing the conflict;
204 $ git diff
206 will show this. Once you’ve edited the files to resolve the conflicts,
209 $ git commit -a
211 will commit the result of the merge. Finally,
214 $ gitk
216 will show a nice graphical representation of the resulting history.
219 At this point you could delete the experimental branch with
221 $ git branch -d experimental
223 This command ensures that the changes in the experimental branch are
226 already in the current branch.
227 If you develop on a branch crazy-idea, then regret it, you can always
229 delete the branch with
230 $ git branch -D crazy-idea
232 Branches are cheap and easy, so this is a good way to try something
235 out.
236
238 Suppose that Alice has started a new project with a Git repository in
239 /home/alice/project, and that Bob, who has a home directory on the same
240 machine, wants to contribute.
241 Bob begins with:
243 bob$ git clone /home/alice/project myrepo
245 This creates a new directory "myrepo" containing a clone of Alice’s
248 repository. The clone is on an equal footing with the original project,
249 possessing its own copy of the original project’s history.
250 Bob then makes some changes and commits them:
252 (edit files)
254 bob$ git commit -a
255 (repeat as necessary)
256 When he’s ready, he tells Alice to pull changes from the repository at
259 /home/bob/myrepo. She does this with:
260 alice$ cd /home/alice/project
262 alice$ git pull /home/bob/myrepo master
263 This merges the changes from Bob’s "master" branch into Alice’s current
266 branch. If Alice has made her own changes in the meantime, then she may
267 need to manually fix any conflicts.
268 The "pull" command thus performs two operations: it fetches changes
270 from a remote branch, then merges them into the current branch.
271 Note that in general, Alice would want her local changes committed
273 before initiating this "pull". If Bob’s work conflicts with what Alice
274 did since their histories forked, Alice will use her working tree and
275 the index to resolve conflicts, and existing local changes will
276 interfere with the conflict resolution process (Git will still perform
277 the fetch but will refuse to merge --- Alice will have to get rid of
278 her local changes in some way and pull again when this happens).
279 Alice can peek at what Bob did without merging first, using the "fetch"
281 command; this allows Alice to inspect what Bob did, using a special
282 symbol "FETCH_HEAD", in order to determine if he has anything worth
283 pulling, like this:
284 alice$ git fetch /home/bob/myrepo master
286 alice$ git log -p HEAD..FETCH_HEAD
287 This operation is safe even if Alice has uncommitted local changes. The
290 range notation "HEAD..FETCH_HEAD" means "show everything that is
291 reachable from the FETCH_HEAD but exclude anything that is reachable
292 from HEAD". Alice already knows everything that leads to her current
293 state (HEAD), and reviews what Bob has in his state (FETCH_HEAD) that
294 she has not seen with this command.
295 If Alice wants to visualize what Bob did since their histories forked
297 she can issue the following command:
298 $ gitk HEAD..FETCH_HEAD
300 This uses the same two-dot range notation we saw earlier with git log.
303 Alice may want to view what both of them did since they forked. She can
305 use three-dot form instead of the two-dot form:
306 $ gitk HEAD...FETCH_HEAD
308 This means "show everything that is reachable from either one, but
311 exclude anything that is reachable from both of them".
312 Please note that these range notation can be used with both gitk and
314 "git log".
315 After inspecting what Bob did, if there is nothing urgent, Alice may
317 decide to continue working without pulling from Bob. If Bob’s history
318 does have something Alice would immediately need, Alice may choose to
319 stash her work-in-progress first, do a "pull", and then finally unstash
320 her work-in-progress on top of the resulting history.
321 When you are working in a small closely knit group, it is not unusual
323 to interact with the same repository over and over again. By defining
324 remote repository shorthand, you can make it easier:
325 alice$ git remote add bob /home/bob/myrepo
327 With this, Alice can perform the first part of the "pull" operation
330 alone using the git fetch command without merging them with her own
331 branch, using:
332 alice$ git fetch bob
334 Unlike the longhand form, when Alice fetches from Bob using a remote
337 repository shorthand set up with git remote, what was fetched is stored
338 in a remote-tracking branch, in this case bob/master. So after this:
339 alice$ git log -p master..bob/master
341 shows a list of all the changes that Bob made since he branched from
344 Alice’s master branch.
345 After examining those changes, Alice could merge the changes into her
347 master branch:
348 alice$ git merge bob/master
350 This merge can also be done by pulling from her own remote-tracking
353 branch, like this:
354 alice$ git pull . remotes/bob/master
356 Note that git pull always merges into the current branch, regardless of
359 what else is given on the command line.
360 Later, Bob can update his repo with Alice’s latest changes using
362 bob$ git pull
364 Note that he doesn’t need to give the path to Alice’s repository; when
367 Bob cloned Alice’s repository, Git stored the location of her
368 repository in the repository configuration, and that location is used
369 for pulls:
370 bob$ git config --get remote.origin.url
372 /home/alice/project
373 (The complete configuration created by git clone is visible using git
376 config -l, and the git-config(1) man page explains the meaning of each
377 option.)
378 Git also keeps a pristine copy of Alice’s master branch under the name
380 "origin/master":
381 bob$ git branch -r
383 origin/master
384 If Bob later decides to work from a different host, he can still
387 perform clones and pulls using the ssh protocol:
388 bob$ git clone alice.org:/home/alice/project myrepo
390 Alternatively, Git has a native protocol, or can use http; see git-
393 pull(1) for details.
394 Git can also be used in a CVS-like mode, with a central repository that
396 various users push changes to; see git-push(1) and gitcvs-migration(7).
397
399 Git history is represented as a series of interrelated commits. We have
400 already seen that the git log command can list those commits. Note that
401 first line of each git log entry also gives a name for the commit:
402 $ git log
404 commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
405 Author: Junio C Hamano <junkio@cox.net>
406 Date: Tue May 16 17:18:22 2006 -0700
407 merge-base: Clarify the comments on post processing.
409 We can give this name to git show to see the details about this commit.
412 $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
414 But there are other ways to refer to commits. You can use any initial
417 part of the name that is long enough to uniquely identify the commit:
418 $ git show c82a22c39c # the first few characters of the name are
420 # usually enough
421 $ git show HEAD # the tip of the current branch
422 $ git show experimental # the tip of the "experimental" branch
423 Every commit usually has one "parent" commit which points to the
426 previous state of the project:
427 $ git show HEAD^ # to see the parent of HEAD
429 $ git show HEAD^^ # to see the grandparent of HEAD
430 $ git show HEAD~4 # to see the great-great grandparent of HEAD
431 Note that merge commits may have more than one parent:
434 $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
436 $ git show HEAD^2 # show the second parent of HEAD
437 You can also give commits names of your own; after running
440 $ git tag v2.5 1b2e1d63ff
442 you can refer to 1b2e1d63ff by the name "v2.5". If you intend to share
445 this name with other people (for example, to identify a release
446 version), you should create a "tag" object, and perhaps sign it; see
447 git-tag(1) for details.
448 Any Git command that needs to know a commit can take any of these
450 names. For example:
451 $ git diff v2.5 HEAD # compare the current HEAD to v2.5
453 $ git branch stable v2.5 # start a new branch named "stable" based
454 # at v2.5
455 $ git reset --hard HEAD^ # reset your current branch and working
456 # directory to its state at HEAD^
457 Be careful with that last command: in addition to losing any changes in
460 the working directory, it will also remove all later commits from this
461 branch. If this branch is the only branch containing those commits,
462 they will be lost. Also, don’t use git reset on a publicly-visible
463 branch that other developers pull from, as it will force needless
464 merges on other developers to clean up the history. If you need to undo
465 changes that you have pushed, use git revert instead.
466 The git grep command can search for strings in any version of your
468 project, so
469 $ git grep "hello" v2.5
471 searches for all occurrences of "hello" in v2.5.
474 If you leave out the commit name, git grep will search any of the files
476 it manages in your current directory. So
477 $ git grep "hello"
479 is a quick way to search just the files that are tracked by Git.
482 Many Git commands also take sets of commits, which can be specified in
484 a number of ways. Here are some examples with git log:
485 $ git log v2.5..v2.6 # commits between v2.5 and v2.6
487 $ git log v2.5.. # commits since v2.5
488 $ git log --since="2 weeks ago" # commits from the last 2 weeks
489 $ git log v2.5.. Makefile # commits since v2.5 which modify
490 # Makefile
491 You can also give git log a "range" of commits where the first is not
494 necessarily an ancestor of the second; for example, if the tips of the
495 branches "stable" and "master" diverged from a common commit some time
496 ago, then
497 $ git log stable..master
499 will list commits made in the master branch but not in the stable
502 branch, while
503 $ git log master..stable
505 will show the list of commits made on the stable branch but not the
508 master branch.
509 The git log command has a weakness: it must present commits in a list.
511 When the history has lines of development that diverged and then merged
512 back together, the order in which git log presents those commits is
513 meaningless.
514 Most projects with multiple contributors (such as the Linux kernel, or
516 Git itself) have frequent merges, and gitk does a better job of
517 visualizing their history. For example,
518 $ gitk --since="2 weeks ago" drivers/
520 allows you to browse any commits from the last 2 weeks of commits that
523 modified files under the "drivers" directory. (Note: you can adjust
524 gitk’s fonts by holding down the control key while pressing "-" or
525 "+".)
526 Finally, most commands that take filenames will optionally allow you to
528 precede any filename by a commit, to specify a particular version of
529 the file:
530 $ git diff v2.5:Makefile HEAD:Makefile.in
532 You can also use git show to see any such file:
535 $ git show v2.5:Makefile
537
540 This tutorial should be enough to perform basic distributed revision
541 control for your projects. However, to fully understand the depth and
542 power of Git you need to understand two simple ideas on which it is
543 based:
544 · The object database is the rather elegant system used to store the
546 history of your project—files, directories, and commits.
547 · The index file is a cache of the state of a directory tree, used to
549 create commits, check out working directories, and hold the various
550 trees involved in a merge.
551 Part two of this tutorial explains the object database, the index file,
553 and a few other odds and ends that you’ll need to make the most of Git.
554 You can find it at gittutorial-2(7).
555 If you don’t want to continue with that right away, a few other
557 digressions that may be interesting at this point are:
558 · git-format-patch(1), git-am(1): These convert series of git commits
560 into emailed patches, and vice versa, useful for projects such as
561 the Linux kernel which rely heavily on emailed patches.
562 · git-bisect(1): When there is a regression in your project, one way
564 to track down the bug is by searching through the history to find
565 the exact commit that’s to blame. Git bisect can help you perform a
566 binary search for that commit. It is smart enough to perform a
567 close-to-optimal search even in the case of complex non-linear
568 history with lots of merged branches.
569 · gitworkflows(7): Gives an overview of recommended workflows.
571 · giteveryday(7): Everyday Git with 20 Commands Or So.
573 · gitcvs-migration(7): Git for CVS users.
575
577 gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
578 gitglossary(7), git-help(1), gitworkflows(7), giteveryday(7), The Git
579 User’s Manual[1]
580
582 Part of the git(1) suite
583
585 1. The Git User’s Manual
586 file:///usr/share/doc/git/user-manual.html
587Git 2.20.1 12/15/2018 GITTUTORIAL(7)