1GITTUTORIAL(7) Git Manual GITTUTORIAL(7)
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6 gittutorial - A tutorial introduction to Git
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9 git *
10
12 This tutorial explains how to import a new project into Git, make
13 changes to it, and share changes with other developers.
14 If you are instead primarily interested in using Git to fetch a
16 project, for example, to test the latest version, you may prefer to
17 start with the first two chapters of The Git User’s Manual[1].
18 First, note that you can get documentation for a command such as git
20 log --graph with:
21 $ man git-log
23 or:
25 $ git help log
27 With the latter, you can use the manual viewer of your choice; see git-
29 help(1) for more information.
30 It is a good idea to introduce yourself to Git with your name and
32 public email address before doing any operation. The easiest way to do
33 so is:
34 $ git config --global user.name "Your Name Comes Here"
36 $ git config --global user.email you@yourdomain.example.com
37
39 Assume you have a tarball project.tar.gz with your initial work. You
40 can place it under Git revision control as follows.
41 $ tar xzf project.tar.gz
43 $ cd project
44 $ git init
45 Git will reply
47 Initialized empty Git repository in .git/
49 You’ve now initialized the working directory—you may notice a new
51 directory created, named .git.
52 Next, tell Git to take a snapshot of the contents of all files under
54 the current directory (note the .), with git add:
55 $ git add .
57 This snapshot is now stored in a temporary staging area which Git calls
59 the "index". You can permanently store the contents of the index in the
60 repository with git commit:
61 $ git commit
63 This will prompt you for a commit message. You’ve now stored the first
65 version of your project in Git.
66
68 Modify some files, then add their updated contents to the index:
69 $ git add file1 file2 file3
71 You are now ready to commit. You can see what is about to be committed
73 using git diff with the --cached option:
74 $ git diff --cached
76 (Without --cached, git diff will show you any changes that you’ve made
78 but not yet added to the index.) You can also get a brief summary of
79 the situation with git status:
80 $ git status
82 On branch master
83 Changes to be committed:
84 (use "git restore --staged <file>..." to unstage)
85 modified: file1
87 modified: file2
88 modified: file3
89 If you need to make any further adjustments, do so now, and then add
91 any newly modified content to the index. Finally, commit your changes
92 with:
93 $ git commit
95 This will again prompt you for a message describing the change, and
97 then record a new version of the project.
98 Alternatively, instead of running git add beforehand, you can use
100 $ git commit -a
102 which will automatically notice any modified (but not new) files, add
104 them to the index, and commit, all in one step.
105 A note on commit messages: Though not required, it’s a good idea to
107 begin the commit message with a single short (no more than 50
108 characters) line summarizing the change, followed by a blank line and
109 then a more thorough description. The text up to the first blank line
110 in a commit message is treated as the commit title, and that title is
111 used throughout Git. For example, git-format-patch(1) turns a commit
112 into email, and it uses the title on the Subject line and the rest of
113 the commit in the body.
114
116 Many revision control systems provide an add command that tells the
117 system to start tracking changes to a new file. Git’s add command does
118 something simpler and more powerful: git add is used both for new and
119 newly modified files, and in both cases it takes a snapshot of the
120 given files and stages that content in the index, ready for inclusion
121 in the next commit.
122
124 At any point you can view the history of your changes using
125 $ git log
127 If you also want to see complete diffs at each step, use
129 $ git log -p
131 Often the overview of the change is useful to get a feel of each step
133 $ git log --stat --summary
135
137 A single Git repository can maintain multiple branches of development.
138 To create a new branch named experimental, use
139 $ git branch experimental
141 If you now run
143 $ git branch
145 you’ll get a list of all existing branches:
147 experimental
149 * master
150 The experimental branch is the one you just created, and the master
152 branch is a default branch that was created for you automatically. The
153 asterisk marks the branch you are currently on; type
154 $ git switch experimental
156 to switch to the experimental branch. Now edit a file, commit the
158 change, and switch back to the master branch:
159 (edit file)
161 $ git commit -a
162 $ git switch master
163 Check that the change you made is no longer visible, since it was made
165 on the experimental branch and you’re back on the master branch.
166 You can make a different change on the master branch:
168 (edit file)
170 $ git commit -a
171 at this point the two branches have diverged, with different changes
173 made in each. To merge the changes made in experimental into master,
174 run
175 $ git merge experimental
177 If the changes don’t conflict, you’re done. If there are conflicts,
179 markers will be left in the problematic files showing the conflict;
180 $ git diff
182 will show this. Once you’ve edited the files to resolve the conflicts,
184 $ git commit -a
186 will commit the result of the merge. Finally,
188 $ gitk
190 will show a nice graphical representation of the resulting history.
192 At this point you could delete the experimental branch with
194 $ git branch -d experimental
196 This command ensures that the changes in the experimental branch are
198 already in the current branch.
199 If you develop on a branch crazy-idea, then regret it, you can always
201 delete the branch with
202 $ git branch -D crazy-idea
204 Branches are cheap and easy, so this is a good way to try something
206 out.
207
209 Suppose that Alice has started a new project with a Git repository in
210 /home/alice/project, and that Bob, who has a home directory on the same
211 machine, wants to contribute.
212 Bob begins with:
214 bob$ git clone /home/alice/project myrepo
216 This creates a new directory myrepo containing a clone of Alice’s
218 repository. The clone is on an equal footing with the original project,
219 possessing its own copy of the original project’s history.
220 Bob then makes some changes and commits them:
222 (edit files)
224 bob$ git commit -a
225 (repeat as necessary)
226 When he’s ready, he tells Alice to pull changes from the repository at
228 /home/bob/myrepo. She does this with:
229 alice$ cd /home/alice/project
231 alice$ git pull /home/bob/myrepo master
232 This merges the changes from Bob’s master branch into Alice’s current
234 branch. If Alice has made her own changes in the meantime, then she may
235 need to manually fix any conflicts.
236 The pull command thus performs two operations: it fetches changes from
238 a remote branch, then merges them into the current branch.
239 Note that in general, Alice would want her local changes committed
241 before initiating this pull. If Bob’s work conflicts with what Alice
242 did since their histories forked, Alice will use her working tree and
243 the index to resolve conflicts, and existing local changes will
244 interfere with the conflict resolution process (Git will still perform
245 the fetch but will refuse to merge — Alice will have to get rid of her
246 local changes in some way and pull again when this happens).
247 Alice can peek at what Bob did without merging first, using the fetch
249 command; this allows Alice to inspect what Bob did, using a special
250 symbol FETCH_HEAD, in order to determine if he has anything worth
251 pulling, like this:
252 alice$ git fetch /home/bob/myrepo master
254 alice$ git log -p HEAD..FETCH_HEAD
255 This operation is safe even if Alice has uncommitted local changes. The
257 range notation HEAD..FETCH_HEAD means "show everything that is
258 reachable from the FETCH_HEAD but exclude anything that is reachable
259 from HEAD". Alice already knows everything that leads to her current
260 state (HEAD), and reviews what Bob has in his state (FETCH_HEAD) that
261 she has not seen with this command.
262 If Alice wants to visualize what Bob did since their histories forked
264 she can issue the following command:
265 $ gitk HEAD..FETCH_HEAD
267 This uses the same two-dot range notation we saw earlier with git log.
269 Alice may want to view what both of them did since they forked. She can
271 use three-dot form instead of the two-dot form:
272 $ gitk HEAD...FETCH_HEAD
274 This means "show everything that is reachable from either one, but
276 exclude anything that is reachable from both of them".
277 Please note that these range notation can be used with both gitk and
279 git log.
280 After inspecting what Bob did, if there is nothing urgent, Alice may
282 decide to continue working without pulling from Bob. If Bob’s history
283 does have something Alice would immediately need, Alice may choose to
284 stash her work-in-progress first, do a pull, and then finally unstash
285 her work-in-progress on top of the resulting history.
286 When you are working in a small closely knit group, it is not unusual
288 to interact with the same repository over and over again. By defining
289 remote repository shorthand, you can make it easier:
290 alice$ git remote add bob /home/bob/myrepo
292 With this, Alice can perform the first part of the pull operation alone
294 using the git fetch command without merging them with her own branch,
295 using:
296 alice$ git fetch bob
298 Unlike the longhand form, when Alice fetches from Bob using a remote
300 repository shorthand set up with git remote, what was fetched is stored
301 in a remote-tracking branch, in this case bob/master. So after this:
302 alice$ git log -p master..bob/master
304 shows a list of all the changes that Bob made since he branched from
306 Alice’s master branch.
307 After examining those changes, Alice could merge the changes into her
309 master branch:
310 alice$ git merge bob/master
312 This merge can also be done by pulling from her own remote-tracking
314 branch, like this:
315 alice$ git pull . remotes/bob/master
317 Note that git pull always merges into the current branch, regardless of
319 what else is given on the command line.
320 Later, Bob can update his repo with Alice’s latest changes using
322 bob$ git pull
324 Note that he doesn’t need to give the path to Alice’s repository; when
326 Bob cloned Alice’s repository, Git stored the location of her
327 repository in the repository configuration, and that location is used
328 for pulls:
329 bob$ git config --get remote.origin.url
331 /home/alice/project
332 (The complete configuration created by git clone is visible using git
334 config -l, and the git-config(1) man page explains the meaning of each
335 option.)
336 Git also keeps a pristine copy of Alice’s master branch under the name
338 origin/master:
339 bob$ git branch -r
341 origin/master
342 If Bob later decides to work from a different host, he can still
344 perform clones and pulls using the ssh protocol:
345 bob$ git clone alice.org:/home/alice/project myrepo
347 Alternatively, Git has a native protocol, or can use http; see git-
349 pull(1) for details.
350 Git can also be used in a CVS-like mode, with a central repository that
352 various users push changes to; see git-push(1) and gitcvs-migration(7).
353
355 Git history is represented as a series of interrelated commits. We have
356 already seen that the git log command can list those commits. Note that
357 first line of each git log entry also gives a name for the commit:
358 $ git log
360 commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
361 Author: Junio C Hamano <junkio@cox.net>
362 Date: Tue May 16 17:18:22 2006 -0700
363 merge-base: Clarify the comments on post processing.
365 We can give this name to git show to see the details about this commit.
367 $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
369 But there are other ways to refer to commits. You can use any initial
371 part of the name that is long enough to uniquely identify the commit:
372 $ git show c82a22c39c # the first few characters of the name are
374 # usually enough
375 $ git show HEAD # the tip of the current branch
376 $ git show experimental # the tip of the "experimental" branch
377 Every commit usually has one "parent" commit which points to the
379 previous state of the project:
380 $ git show HEAD^ # to see the parent of HEAD
382 $ git show HEAD^^ # to see the grandparent of HEAD
383 $ git show HEAD~4 # to see the great-great grandparent of HEAD
384 Note that merge commits may have more than one parent:
386 $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
388 $ git show HEAD^2 # show the second parent of HEAD
389 You can also give commits names of your own; after running
391 $ git tag v2.5 1b2e1d63ff
393 you can refer to 1b2e1d63ff by the name v2.5. If you intend to share
395 this name with other people (for example, to identify a release
396 version), you should create a "tag" object, and perhaps sign it; see
397 git-tag(1) for details.
398 Any Git command that needs to know a commit can take any of these
400 names. For example:
401 $ git diff v2.5 HEAD # compare the current HEAD to v2.5
403 $ git branch stable v2.5 # start a new branch named "stable" based
404 # at v2.5
405 $ git reset --hard HEAD^ # reset your current branch and working
406 # directory to its state at HEAD^
407 Be careful with that last command: in addition to losing any changes in
409 the working directory, it will also remove all later commits from this
410 branch. If this branch is the only branch containing those commits,
411 they will be lost. Also, don’t use git reset on a publicly-visible
412 branch that other developers pull from, as it will force needless
413 merges on other developers to clean up the history. If you need to undo
414 changes that you have pushed, use git revert instead.
415 The git grep command can search for strings in any version of your
417 project, so
418 $ git grep "hello" v2.5
420 searches for all occurrences of "hello" in v2.5.
422 If you leave out the commit name, git grep will search any of the files
424 it manages in your current directory. So
425 $ git grep "hello"
427 is a quick way to search just the files that are tracked by Git.
429 Many Git commands also take sets of commits, which can be specified in
431 a number of ways. Here are some examples with git log:
432 $ git log v2.5..v2.6 # commits between v2.5 and v2.6
434 $ git log v2.5.. # commits since v2.5
435 $ git log --since="2 weeks ago" # commits from the last 2 weeks
436 $ git log v2.5.. Makefile # commits since v2.5 which modify
437 # Makefile
438 You can also give git log a "range" of commits where the first is not
440 necessarily an ancestor of the second; for example, if the tips of the
441 branches stable and master diverged from a common commit some time ago,
442 then
443 $ git log stable..master
445 will list commits made in the master branch but not in the stable
447 branch, while
448 $ git log master..stable
450 will show the list of commits made on the stable branch but not the
452 master branch.
453 The git log command has a weakness: it must present commits in a list.
455 When the history has lines of development that diverged and then merged
456 back together, the order in which git log presents those commits is
457 meaningless.
458 Most projects with multiple contributors (such as the Linux kernel, or
460 Git itself) have frequent merges, and gitk does a better job of
461 visualizing their history. For example,
462 $ gitk --since="2 weeks ago" drivers/
464 allows you to browse any commits from the last 2 weeks of commits that
466 modified files under the drivers directory. (Note: you can adjust
467 gitk’s fonts by holding down the control key while pressing "-" or
468 "+".)
469 Finally, most commands that take filenames will optionally allow you to
471 precede any filename by a commit, to specify a particular version of
472 the file:
473 $ git diff v2.5:Makefile HEAD:Makefile.in
475 You can also use git show to see any such file:
477 $ git show v2.5:Makefile
479
481 This tutorial should be enough to perform basic distributed revision
482 control for your projects. However, to fully understand the depth and
483 power of Git you need to understand two simple ideas on which it is
484 based:
485 • The object database is the rather elegant system used to store the
487 history of your project—files, directories, and commits.
488 • The index file is a cache of the state of a directory tree, used to
490 create commits, check out working directories, and hold the various
491 trees involved in a merge.
492 Part two of this tutorial explains the object database, the index file,
494 and a few other odds and ends that you’ll need to make the most of Git.
495 You can find it at gittutorial-2(7).
496 If you don’t want to continue with that right away, a few other
498 digressions that may be interesting at this point are:
499 • git-format-patch(1), git-am(1): These convert series of git commits
501 into emailed patches, and vice versa, useful for projects such as
502 the Linux kernel which rely heavily on emailed patches.
503 • git-bisect(1): When there is a regression in your project, one way
505 to track down the bug is by searching through the history to find
506 the exact commit that’s to blame. git bisect can help you perform
507 a binary search for that commit. It is smart enough to perform a
508 close-to-optimal search even in the case of complex non-linear
509 history with lots of merged branches.
510 • gitworkflows(7): Gives an overview of recommended workflows.
512 • giteveryday(7): Everyday Git with 20 Commands Or So.
514 • gitcvs-migration(7): Git for CVS users.
516
518 gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
519 gitglossary(7), git-help(1), gitworkflows(7), giteveryday(7), The Git
520 User’s Manual[1]
521
523 Part of the git(1) suite
524
526 1. The Git User’s Manual
527 file:///usr/share/doc/git/user-manual.html
528Git 2.43.0 11/20/2023 GITTUTORIAL(7)