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 Your branch is up to date with 'origin/master'.
85 (use "git restore --staged <file>..." to unstage)
86 modified: file1
88 modified: file2
89 modified: file3
90 If you need to make any further adjustments, do so now, and then add
92 any newly modified content to the index. Finally, commit your changes
93 with:
94 $ git commit
96 This will again prompt you for a message describing the change, and
98 then record a new version of the project.
99 Alternatively, instead of running git add beforehand, you can use
101 $ git commit -a
103 which will automatically notice any modified (but not new) files, add
105 them to the index, and commit, all in one step.
106 A note on commit messages: Though not required, it’s a good idea to
108 begin the commit message with a single short (less than 50 character)
109 line summarizing the change, followed by a blank line and then a more
110 thorough description. The text up to the first blank line in a commit
111 message is treated as the commit title, and that title is used
112 throughout Git. For example, git-format-patch(1) turns a commit into
113 email, and it uses the title on the Subject line and the rest of the
114 commit in the body.
115
117 Many revision control systems provide an add command that tells the
118 system to start tracking changes to a new file. Git’s add command does
119 something simpler and more powerful: git add is used both for new and
120 newly modified files, and in both cases it takes a snapshot of the
121 given files and stages that content in the index, ready for inclusion
122 in the next commit.
123
125 At any point you can view the history of your changes using
126 $ git log
128 If you also want to see complete diffs at each step, use
130 $ git log -p
132 Often the overview of the change is useful to get a feel of each step
134 $ git log --stat --summary
136
138 A single Git repository can maintain multiple branches of development.
139 To create a new branch named "experimental", use
140 $ git branch experimental
142 If you now run
144 $ git branch
146 you’ll get a list of all existing branches:
148 experimental
150 * master
151 The "experimental" branch is the one you just created, and the "master"
153 branch is a default branch that was created for you automatically. The
154 asterisk marks the branch you are currently on; type
155 $ git switch experimental
157 to switch to the experimental branch. Now edit a file, commit the
159 change, and switch back to the master branch:
160 (edit file)
162 $ git commit -a
163 $ git switch master
164 Check that the change you made is no longer visible, since it was made
166 on the experimental branch and you’re back on the master branch.
167 You can make a different change on the master branch:
169 (edit file)
171 $ git commit -a
172 at this point the two branches have diverged, with different changes
174 made in each. To merge the changes made in experimental into master,
175 run
176 $ git merge experimental
178 If the changes don’t conflict, you’re done. If there are conflicts,
180 markers will be left in the problematic files showing the conflict;
181 $ git diff
183 will show this. Once you’ve edited the files to resolve the conflicts,
185 $ git commit -a
187 will commit the result of the merge. Finally,
189 $ gitk
191 will show a nice graphical representation of the resulting history.
193 At this point you could delete the experimental branch with
195 $ git branch -d experimental
197 This command ensures that the changes in the experimental branch are
199 already in the current branch.
200 If you develop on a branch crazy-idea, then regret it, you can always
202 delete the branch with
203 $ git branch -D crazy-idea
205 Branches are cheap and easy, so this is a good way to try something
207 out.
208
210 Suppose that Alice has started a new project with a Git repository in
211 /home/alice/project, and that Bob, who has a home directory on the same
212 machine, wants to contribute.
213 Bob begins with:
215 bob$ git clone /home/alice/project myrepo
217 This creates a new directory "myrepo" containing a clone of Alice’s
219 repository. The clone is on an equal footing with the original project,
220 possessing its own copy of the original project’s history.
221 Bob then makes some changes and commits them:
223 (edit files)
225 bob$ git commit -a
226 (repeat as necessary)
227 When he’s ready, he tells Alice to pull changes from the repository at
229 /home/bob/myrepo. She does this with:
230 alice$ cd /home/alice/project
232 alice$ git pull /home/bob/myrepo master
233 This merges the changes from Bob’s "master" branch into Alice’s current
235 branch. If Alice has made her own changes in the meantime, then she may
236 need to manually fix any conflicts.
237 The "pull" command thus performs two operations: it fetches changes
239 from a remote branch, then merges them into the current branch.
240 Note that in general, Alice would want her local changes committed
242 before initiating this "pull". If Bob’s work conflicts with what Alice
243 did since their histories forked, Alice will use her working tree and
244 the index to resolve conflicts, and existing local changes will
245 interfere with the conflict resolution process (Git will still perform
246 the fetch but will refuse to merge — Alice will have to get rid of her
247 local changes in some way and pull again when this happens).
248 Alice can peek at what Bob did without merging first, using the "fetch"
250 command; this allows Alice to inspect what Bob did, using a special
251 symbol "FETCH_HEAD", in order to determine if he has anything worth
252 pulling, like this:
253 alice$ git fetch /home/bob/myrepo master
255 alice$ git log -p HEAD..FETCH_HEAD
256 This operation is safe even if Alice has uncommitted local changes. The
258 range notation "HEAD..FETCH_HEAD" means "show everything that is
259 reachable from the FETCH_HEAD but exclude anything that is reachable
260 from HEAD". Alice already knows everything that leads to her current
261 state (HEAD), and reviews what Bob has in his state (FETCH_HEAD) that
262 she has not seen with this command.
263 If Alice wants to visualize what Bob did since their histories forked
265 she can issue the following command:
266 $ gitk HEAD..FETCH_HEAD
268 This uses the same two-dot range notation we saw earlier with git log.
270 Alice may want to view what both of them did since they forked. She can
272 use three-dot form instead of the two-dot form:
273 $ gitk HEAD...FETCH_HEAD
275 This means "show everything that is reachable from either one, but
277 exclude anything that is reachable from both of them".
278 Please note that these range notation can be used with both gitk and
280 "git log".
281 After inspecting what Bob did, if there is nothing urgent, Alice may
283 decide to continue working without pulling from Bob. If Bob’s history
284 does have something Alice would immediately need, Alice may choose to
285 stash her work-in-progress first, do a "pull", and then finally unstash
286 her work-in-progress on top of the resulting history.
287 When you are working in a small closely knit group, it is not unusual
289 to interact with the same repository over and over again. By defining
290 remote repository shorthand, you can make it easier:
291 alice$ git remote add bob /home/bob/myrepo
293 With this, Alice can perform the first part of the "pull" operation
295 alone using the git fetch command without merging them with her own
296 branch, using:
297 alice$ git fetch bob
299 Unlike the longhand form, when Alice fetches from Bob using a remote
301 repository shorthand set up with git remote, what was fetched is stored
302 in a remote-tracking branch, in this case bob/master. So after this:
303 alice$ git log -p master..bob/master
305 shows a list of all the changes that Bob made since he branched from
307 Alice’s master branch.
308 After examining those changes, Alice could merge the changes into her
310 master branch:
311 alice$ git merge bob/master
313 This merge can also be done by pulling from her own remote-tracking
315 branch, like this:
316 alice$ git pull . remotes/bob/master
318 Note that git pull always merges into the current branch, regardless of
320 what else is given on the command line.
321 Later, Bob can update his repo with Alice’s latest changes using
323 bob$ git pull
325 Note that he doesn’t need to give the path to Alice’s repository; when
327 Bob cloned Alice’s repository, Git stored the location of her
328 repository in the repository configuration, and that location is used
329 for pulls:
330 bob$ git config --get remote.origin.url
332 /home/alice/project
333 (The complete configuration created by git clone is visible using git
335 config -l, and the git-config(1) man page explains the meaning of each
336 option.)
337 Git also keeps a pristine copy of Alice’s master branch under the name
339 "origin/master":
340 bob$ git branch -r
342 origin/master
343 If Bob later decides to work from a different host, he can still
345 perform clones and pulls using the ssh protocol:
346 bob$ git clone alice.org:/home/alice/project myrepo
348 Alternatively, Git has a native protocol, or can use http; see git-
350 pull(1) for details.
351 Git can also be used in a CVS-like mode, with a central repository that
353 various users push changes to; see git-push(1) and gitcvs-migration(7).
354
356 Git history is represented as a series of interrelated commits. We have
357 already seen that the git log command can list those commits. Note that
358 first line of each git log entry also gives a name for the commit:
359 $ git log
361 commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
362 Author: Junio C Hamano <junkio@cox.net>
363 Date: Tue May 16 17:18:22 2006 -0700
364 merge-base: Clarify the comments on post processing.
366 We can give this name to git show to see the details about this commit.
368 $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
370 But there are other ways to refer to commits. You can use any initial
372 part of the name that is long enough to uniquely identify the commit:
373 $ git show c82a22c39c # the first few characters of the name are
375 # usually enough
376 $ git show HEAD # the tip of the current branch
377 $ git show experimental # the tip of the "experimental" branch
378 Every commit usually has one "parent" commit which points to the
380 previous state of the project:
381 $ git show HEAD^ # to see the parent of HEAD
383 $ git show HEAD^^ # to see the grandparent of HEAD
384 $ git show HEAD~4 # to see the great-great grandparent of HEAD
385 Note that merge commits may have more than one parent:
387 $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
389 $ git show HEAD^2 # show the second parent of HEAD
390 You can also give commits names of your own; after running
392 $ git tag v2.5 1b2e1d63ff
394 you can refer to 1b2e1d63ff by the name "v2.5". If you intend to share
396 this name with other people (for example, to identify a release
397 version), you should create a "tag" object, and perhaps sign it; see
398 git-tag(1) for details.
399 Any Git command that needs to know a commit can take any of these
401 names. For example:
402 $ git diff v2.5 HEAD # compare the current HEAD to v2.5
404 $ git branch stable v2.5 # start a new branch named "stable" based
405 # at v2.5
406 $ git reset --hard HEAD^ # reset your current branch and working
407 # directory to its state at HEAD^
408 Be careful with that last command: in addition to losing any changes in
410 the working directory, it will also remove all later commits from this
411 branch. If this branch is the only branch containing those commits,
412 they will be lost. Also, don’t use git reset on a publicly-visible
413 branch that other developers pull from, as it will force needless
414 merges on other developers to clean up the history. If you need to undo
415 changes that you have pushed, use git revert instead.
416 The git grep command can search for strings in any version of your
418 project, so
419 $ git grep "hello" v2.5
421 searches for all occurrences of "hello" in v2.5.
423 If you leave out the commit name, git grep will search any of the files
425 it manages in your current directory. So
426 $ git grep "hello"
428 is a quick way to search just the files that are tracked by Git.
430 Many Git commands also take sets of commits, which can be specified in
432 a number of ways. Here are some examples with git log:
433 $ git log v2.5..v2.6 # commits between v2.5 and v2.6
435 $ git log v2.5.. # commits since v2.5
436 $ git log --since="2 weeks ago" # commits from the last 2 weeks
437 $ git log v2.5.. Makefile # commits since v2.5 which modify
438 # Makefile
439 You can also give git log a "range" of commits where the first is not
441 necessarily an ancestor of the second; for example, if the tips of the
442 branches "stable" and "master" diverged from a common commit some time
443 ago, then
444 $ git log stable..master
446 will list commits made in the master branch but not in the stable
448 branch, while
449 $ git log master..stable
451 will show the list of commits made on the stable branch but not the
453 master branch.
454 The git log command has a weakness: it must present commits in a list.
456 When the history has lines of development that diverged and then merged
457 back together, the order in which git log presents those commits is
458 meaningless.
459 Most projects with multiple contributors (such as the Linux kernel, or
461 Git itself) have frequent merges, and gitk does a better job of
462 visualizing their history. For example,
463 $ gitk --since="2 weeks ago" drivers/
465 allows you to browse any commits from the last 2 weeks of commits that
467 modified files under the "drivers" directory. (Note: you can adjust
468 gitk’s fonts by holding down the control key while pressing "-" or
469 "+".)
470 Finally, most commands that take filenames will optionally allow you to
472 precede any filename by a commit, to specify a particular version of
473 the file:
474 $ git diff v2.5:Makefile HEAD:Makefile.in
476 You can also use git show to see any such file:
478 $ git show v2.5:Makefile
480
482 This tutorial should be enough to perform basic distributed revision
483 control for your projects. However, to fully understand the depth and
484 power of Git you need to understand two simple ideas on which it is
485 based:
486 • The object database is the rather elegant system used to store the
488 history of your project—files, directories, and commits.
489 • The index file is a cache of the state of a directory tree, used to
491 create commits, check out working directories, and hold the various
492 trees involved in a merge.
493 Part two of this tutorial explains the object database, the index file,
495 and a few other odds and ends that you’ll need to make the most of Git.
496 You can find it at gittutorial-2(7).
497 If you don’t want to continue with that right away, a few other
499 digressions that may be interesting at this point are:
500 • git-format-patch(1), git-am(1): These convert series of git commits
502 into emailed patches, and vice versa, useful for projects such as
503 the Linux kernel which rely heavily on emailed patches.
504 • git-bisect(1): When there is a regression in your project, one way
506 to track down the bug is by searching through the history to find
507 the exact commit that’s to blame. Git bisect can help you perform a
508 binary search for that commit. It is smart enough to perform a
509 close-to-optimal search even in the case of complex non-linear
510 history with lots of merged branches.
511 • gitworkflows(7): Gives an overview of recommended workflows.
513 • giteveryday(7): Everyday Git with 20 Commands Or So.
515 • gitcvs-migration(7): Git for CVS users.
517
519 gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
520 gitglossary(7), git-help(1), gitworkflows(7), giteveryday(7), The Git
521 User’s Manual[1]
522
524 Part of the git(1) suite
525
527 1. The Git User’s Manual
528 file:///usr/share/doc/git/user-manual.html
529Git 2.39.1 2023-01-13 GITTUTORIAL(7)