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    1 gittutorial(7)
    2 ==============
    3 
    4 NAME
    5 ----
    6 gittutorial - A tutorial introduction to Git
    7 
    8 SYNOPSIS
    9 --------
   10 [verse]
   11 git *
   12 
   13 DESCRIPTION
   14 -----------
   15 
   16 This tutorial explains how to import a new project into Git, make
   17 changes to it, and share changes with other developers.
   18 
   19 If you are instead primarily interested in using Git to fetch a project,
   20 for example, to test the latest version, you may prefer to start with
   21 the first two chapters of link:user-manual.html[The Git User's Manual].
   22 
   23 First, note that you can get documentation for a command such as
   24 `git log --graph` with:
   25 
   26 ------------------------------------------------
   27 $ man git-log
   28 ------------------------------------------------
   29 
   30 or:
   31 
   32 ------------------------------------------------
   33 $ git help log
   34 ------------------------------------------------
   35 
   36 With the latter, you can use the manual viewer of your choice; see
   37 linkgit:git-help[1] for more information.
   38 
   39 It is a good idea to introduce yourself to Git with your name and
   40 public email address before doing any operation.  The easiest
   41 way to do so is:
   42 
   43 ------------------------------------------------
   44 $ git config --global user.name "Your Name Comes Here"
   45 $ git config --global user.email you@yourdomain.example.com
   46 ------------------------------------------------
   47 
   48 
   49 Importing a new project
   50 -----------------------
   51 
   52 Assume you have a tarball project.tar.gz with your initial work.  You
   53 can place it under Git revision control as follows.
   54 
   55 ------------------------------------------------
   56 $ tar xzf project.tar.gz
   57 $ cd project
   58 $ git init
   59 ------------------------------------------------
   60 
   61 Git will reply
   62 
   63 ------------------------------------------------
   64 Initialized empty Git repository in .git/
   65 ------------------------------------------------
   66 
   67 You've now initialized the working directory--you may notice a new
   68 directory created, named ".git".
   69 
   70 Next, tell Git to take a snapshot of the contents of all files under the
   71 current directory (note the '.'), with 'git add':
   72 
   73 ------------------------------------------------
   74 $ git add .
   75 ------------------------------------------------
   76 
   77 This snapshot is now stored in a temporary staging area which Git calls
   78 the "index".  You can permanently store the contents of the index in the
   79 repository with 'git commit':
   80 
   81 ------------------------------------------------
   82 $ git commit
   83 ------------------------------------------------
   84 
   85 This will prompt you for a commit message.  You've now stored the first
   86 version of your project in Git.
   87 
   88 Making changes
   89 --------------
   90 
   91 Modify some files, then add their updated contents to the index:
   92 
   93 ------------------------------------------------
   94 $ git add file1 file2 file3
   95 ------------------------------------------------
   96 
   97 You are now ready to commit.  You can see what is about to be committed
   98 using 'git diff' with the --cached option:
   99 
  100 ------------------------------------------------
  101 $ git diff --cached
  102 ------------------------------------------------
  103 
  104 (Without --cached, 'git diff' will show you any changes that
  105 you've made but not yet added to the index.)  You can also get a brief
  106 summary of the situation with 'git status':
  107 
  108 ------------------------------------------------
  109 $ git status
  110 On branch master
  111 Changes to be committed:
  112 Your branch is up to date with 'origin/master'.
  113   (use "git restore --staged <file>..." to unstage)
  114 
  115 	modified:   file1
  116 	modified:   file2
  117 	modified:   file3
  118 
  119 ------------------------------------------------
  120 
  121 If you need to make any further adjustments, do so now, and then add any
  122 newly modified content to the index.  Finally, commit your changes with:
  123 
  124 ------------------------------------------------
  125 $ git commit
  126 ------------------------------------------------
  127 
  128 This will again prompt you for a message describing the change, and then
  129 record a new version of the project.
  130 
  131 Alternatively, instead of running 'git add' beforehand, you can use
  132 
  133 ------------------------------------------------
  134 $ git commit -a
  135 ------------------------------------------------
  136 
  137 which will automatically notice any modified (but not new) files, add
  138 them to the index, and commit, all in one step.
  139 
  140 A note on commit messages: Though not required, it's a good idea to
  141 begin the commit message with a single short (less than 50 character)
  142 line summarizing the change, followed by a blank line and then a more
  143 thorough description. The text up to the first blank line in a commit
  144 message is treated as the commit title, and that title is used
  145 throughout Git.  For example, linkgit:git-format-patch[1] turns a
  146 commit into email, and it uses the title on the Subject line and the
  147 rest of the commit in the body.
  148 
  149 Git tracks content not files
  150 ----------------------------
  151 
  152 Many revision control systems provide an `add` command that tells the
  153 system to start tracking changes to a new file.  Git's `add` command
  154 does something simpler and more powerful: 'git add' is used both for new
  155 and newly modified files, and in both cases it takes a snapshot of the
  156 given files and stages that content in the index, ready for inclusion in
  157 the next commit.
  158 
  159 Viewing project history
  160 -----------------------
  161 
  162 At any point you can view the history of your changes using
  163 
  164 ------------------------------------------------
  165 $ git log
  166 ------------------------------------------------
  167 
  168 If you also want to see complete diffs at each step, use
  169 
  170 ------------------------------------------------
  171 $ git log -p
  172 ------------------------------------------------
  173 
  174 Often the overview of the change is useful to get a feel of
  175 each step
  176 
  177 ------------------------------------------------
  178 $ git log --stat --summary
  179 ------------------------------------------------
  180 
  181 Managing branches
  182 -----------------
  183 
  184 A single Git repository can maintain multiple branches of
  185 development.  To create a new branch named "experimental", use
  186 
  187 ------------------------------------------------
  188 $ git branch experimental
  189 ------------------------------------------------
  190 
  191 If you now run
  192 
  193 ------------------------------------------------
  194 $ git branch
  195 ------------------------------------------------
  196 
  197 you'll get a list of all existing branches:
  198 
  199 ------------------------------------------------
  200   experimental
  201 * master
  202 ------------------------------------------------
  203 
  204 The "experimental" branch is the one you just created, and the
  205 "master" branch is a default branch that was created for you
  206 automatically.  The asterisk marks the branch you are currently on;
  207 type
  208 
  209 ------------------------------------------------
  210 $ git switch experimental
  211 ------------------------------------------------
  212 
  213 to switch to the experimental branch.  Now edit a file, commit the
  214 change, and switch back to the master branch:
  215 
  216 ------------------------------------------------
  217 (edit file)
  218 $ git commit -a
  219 $ git switch master
  220 ------------------------------------------------
  221 
  222 Check that the change you made is no longer visible, since it was
  223 made on the experimental branch and you're back on the master branch.
  224 
  225 You can make a different change on the master branch:
  226 
  227 ------------------------------------------------
  228 (edit file)
  229 $ git commit -a
  230 ------------------------------------------------
  231 
  232 at this point the two branches have diverged, with different changes
  233 made in each.  To merge the changes made in experimental into master, run
  234 
  235 ------------------------------------------------
  236 $ git merge experimental
  237 ------------------------------------------------
  238 
  239 If the changes don't conflict, you're done.  If there are conflicts,
  240 markers will be left in the problematic files showing the conflict;
  241 
  242 ------------------------------------------------
  243 $ git diff
  244 ------------------------------------------------
  245 
  246 will show this.  Once you've edited the files to resolve the
  247 conflicts,
  248 
  249 ------------------------------------------------
  250 $ git commit -a
  251 ------------------------------------------------
  252 
  253 will commit the result of the merge. Finally,
  254 
  255 ------------------------------------------------
  256 $ gitk
  257 ------------------------------------------------
  258 
  259 will show a nice graphical representation of the resulting history.
  260 
  261 At this point you could delete the experimental branch with
  262 
  263 ------------------------------------------------
  264 $ git branch -d experimental
  265 ------------------------------------------------
  266 
  267 This command ensures that the changes in the experimental branch are
  268 already in the current branch.
  269 
  270 If you develop on a branch crazy-idea, then regret it, you can always
  271 delete the branch with
  272 
  273 -------------------------------------
  274 $ git branch -D crazy-idea
  275 -------------------------------------
  276 
  277 Branches are cheap and easy, so this is a good way to try something
  278 out.
  279 
  280 Using Git for collaboration
  281 ---------------------------
  282 
  283 Suppose that Alice has started a new project with a Git repository in
  284 /home/alice/project, and that Bob, who has a home directory on the
  285 same machine, wants to contribute.
  286 
  287 Bob begins with:
  288 
  289 ------------------------------------------------
  290 bob$ git clone /home/alice/project myrepo
  291 ------------------------------------------------
  292 
  293 This creates a new directory "myrepo" containing a clone of Alice's
  294 repository.  The clone is on an equal footing with the original
  295 project, possessing its own copy of the original project's history.
  296 
  297 Bob then makes some changes and commits them:
  298 
  299 ------------------------------------------------
  300 (edit files)
  301 bob$ git commit -a
  302 (repeat as necessary)
  303 ------------------------------------------------
  304 
  305 When he's ready, he tells Alice to pull changes from the repository
  306 at /home/bob/myrepo.  She does this with:
  307 
  308 ------------------------------------------------
  309 alice$ cd /home/alice/project
  310 alice$ git pull /home/bob/myrepo master
  311 ------------------------------------------------
  312 
  313 This merges the changes from Bob's "master" branch into Alice's
  314 current branch.  If Alice has made her own changes in the meantime,
  315 then she may need to manually fix any conflicts.
  316 
  317 The "pull" command thus performs two operations: it fetches changes
  318 from a remote branch, then merges them into the current branch.
  319 
  320 Note that in general, Alice would want her local changes committed before
  321 initiating this "pull".  If Bob's work conflicts with what Alice did since
  322 their histories forked, Alice will use her working tree and the index to
  323 resolve conflicts, and existing local changes will interfere with the
  324 conflict resolution process (Git will still perform the fetch but will
  325 refuse to merge --- Alice will have to get rid of her local changes in
  326 some way and pull again when this happens).
  327 
  328 Alice can peek at what Bob did without merging first, using the "fetch"
  329 command; this allows Alice to inspect what Bob did, using a special
  330 symbol "FETCH_HEAD", in order to determine if he has anything worth
  331 pulling, like this:
  332 
  333 ------------------------------------------------
  334 alice$ git fetch /home/bob/myrepo master
  335 alice$ git log -p HEAD..FETCH_HEAD
  336 ------------------------------------------------
  337 
  338 This operation is safe even if Alice has uncommitted local changes.
  339 The range notation "HEAD..FETCH_HEAD" means "show everything that is reachable
  340 from the FETCH_HEAD but exclude anything that is reachable from HEAD".
  341 Alice already knows everything that leads to her current state (HEAD),
  342 and reviews what Bob has in his state (FETCH_HEAD) that she has not
  343 seen with this command.
  344 
  345 If Alice wants to visualize what Bob did since their histories forked
  346 she can issue the following command:
  347 
  348 ------------------------------------------------
  349 $ gitk HEAD..FETCH_HEAD
  350 ------------------------------------------------
  351 
  352 This uses the same two-dot range notation we saw earlier with 'git log'.
  353 
  354 Alice may want to view what both of them did since they forked.
  355 She can use three-dot form instead of the two-dot form:
  356 
  357 ------------------------------------------------
  358 $ gitk HEAD...FETCH_HEAD
  359 ------------------------------------------------
  360 
  361 This means "show everything that is reachable from either one, but
  362 exclude anything that is reachable from both of them".
  363 
  364 Please note that these range notation can be used with both gitk
  365 and "git log".
  366 
  367 After inspecting what Bob did, if there is nothing urgent, Alice may
  368 decide to continue working without pulling from Bob.  If Bob's history
  369 does have something Alice would immediately need, Alice may choose to
  370 stash her work-in-progress first, do a "pull", and then finally unstash
  371 her work-in-progress on top of the resulting history.
  372 
  373 When you are working in a small closely knit group, it is not
  374 unusual to interact with the same repository over and over
  375 again.  By defining 'remote' repository shorthand, you can make
  376 it easier:
  377 
  378 ------------------------------------------------
  379 alice$ git remote add bob /home/bob/myrepo
  380 ------------------------------------------------
  381 
  382 With this, Alice can perform the first part of the "pull" operation
  383 alone using the 'git fetch' command without merging them with her own
  384 branch, using:
  385 
  386 -------------------------------------
  387 alice$ git fetch bob
  388 -------------------------------------
  389 
  390 Unlike the longhand form, when Alice fetches from Bob using a
  391 remote repository shorthand set up with 'git remote', what was
  392 fetched is stored in a remote-tracking branch, in this case
  393 `bob/master`.  So after this:
  394 
  395 -------------------------------------
  396 alice$ git log -p master..bob/master
  397 -------------------------------------
  398 
  399 shows a list of all the changes that Bob made since he branched from
  400 Alice's master branch.
  401 
  402 After examining those changes, Alice
  403 could merge the changes into her master branch:
  404 
  405 -------------------------------------
  406 alice$ git merge bob/master
  407 -------------------------------------
  408 
  409 This `merge` can also be done by 'pulling from her own remote-tracking
  410 branch', like this:
  411 
  412 -------------------------------------
  413 alice$ git pull . remotes/bob/master
  414 -------------------------------------
  415 
  416 Note that git pull always merges into the current branch,
  417 regardless of what else is given on the command line.
  418 
  419 Later, Bob can update his repo with Alice's latest changes using
  420 
  421 -------------------------------------
  422 bob$ git pull
  423 -------------------------------------
  424 
  425 Note that he doesn't need to give the path to Alice's repository;
  426 when Bob cloned Alice's repository, Git stored the location of her
  427 repository in the repository configuration, and that location is
  428 used for pulls:
  429 
  430 -------------------------------------
  431 bob$ git config --get remote.origin.url
  432 /home/alice/project
  433 -------------------------------------
  434 
  435 (The complete configuration created by 'git clone' is visible using
  436 `git config -l`, and the linkgit:git-config[1] man page
  437 explains the meaning of each option.)
  438 
  439 Git also keeps a pristine copy of Alice's master branch under the
  440 name "origin/master":
  441 
  442 -------------------------------------
  443 bob$ git branch -r
  444   origin/master
  445 -------------------------------------
  446 
  447 If Bob later decides to work from a different host, he can still
  448 perform clones and pulls using the ssh protocol:
  449 
  450 -------------------------------------
  451 bob$ git clone alice.org:/home/alice/project myrepo
  452 -------------------------------------
  453 
  454 Alternatively, Git has a native protocol, or can use http;
  455 see linkgit:git-pull[1] for details.
  456 
  457 Git can also be used in a CVS-like mode, with a central repository
  458 that various users push changes to; see linkgit:git-push[1] and
  459 linkgit:gitcvs-migration[7].
  460 
  461 Exploring history
  462 -----------------
  463 
  464 Git history is represented as a series of interrelated commits.  We
  465 have already seen that the 'git log' command can list those commits.
  466 Note that first line of each git log entry also gives a name for the
  467 commit:
  468 
  469 -------------------------------------
  470 $ git log
  471 commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
  472 Author: Junio C Hamano <junkio@cox.net>
  473 Date:   Tue May 16 17:18:22 2006 -0700
  474 
  475     merge-base: Clarify the comments on post processing.
  476 -------------------------------------
  477 
  478 We can give this name to 'git show' to see the details about this
  479 commit.
  480 
  481 -------------------------------------
  482 $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
  483 -------------------------------------
  484 
  485 But there are other ways to refer to commits.  You can use any initial
  486 part of the name that is long enough to uniquely identify the commit:
  487 
  488 -------------------------------------
  489 $ git show c82a22c39c	# the first few characters of the name are
  490 			# usually enough
  491 $ git show HEAD		# the tip of the current branch
  492 $ git show experimental	# the tip of the "experimental" branch
  493 -------------------------------------
  494 
  495 Every commit usually has one "parent" commit
  496 which points to the previous state of the project:
  497 
  498 -------------------------------------
  499 $ git show HEAD^  # to see the parent of HEAD
  500 $ git show HEAD^^ # to see the grandparent of HEAD
  501 $ git show HEAD~4 # to see the great-great grandparent of HEAD
  502 -------------------------------------
  503 
  504 Note that merge commits may have more than one parent:
  505 
  506 -------------------------------------
  507 $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
  508 $ git show HEAD^2 # show the second parent of HEAD
  509 -------------------------------------
  510 
  511 You can also give commits names of your own; after running
  512 
  513 -------------------------------------
  514 $ git tag v2.5 1b2e1d63ff
  515 -------------------------------------
  516 
  517 you can refer to 1b2e1d63ff by the name "v2.5".  If you intend to
  518 share this name with other people (for example, to identify a release
  519 version), you should create a "tag" object, and perhaps sign it; see
  520 linkgit:git-tag[1] for details.
  521 
  522 Any Git command that needs to know a commit can take any of these
  523 names.  For example:
  524 
  525 -------------------------------------
  526 $ git diff v2.5 HEAD	 # compare the current HEAD to v2.5
  527 $ git branch stable v2.5 # start a new branch named "stable" based
  528 			 # at v2.5
  529 $ git reset --hard HEAD^ # reset your current branch and working
  530 			 # directory to its state at HEAD^
  531 -------------------------------------
  532 
  533 Be careful with that last command: in addition to losing any changes
  534 in the working directory, it will also remove all later commits from
  535 this branch.  If this branch is the only branch containing those
  536 commits, they will be lost.  Also, don't use 'git reset' on a
  537 publicly-visible branch that other developers pull from, as it will
  538 force needless merges on other developers to clean up the history.
  539 If you need to undo changes that you have pushed, use 'git revert'
  540 instead.
  541 
  542 The 'git grep' command can search for strings in any version of your
  543 project, so
  544 
  545 -------------------------------------
  546 $ git grep "hello" v2.5
  547 -------------------------------------
  548 
  549 searches for all occurrences of "hello" in v2.5.
  550 
  551 If you leave out the commit name, 'git grep' will search any of the
  552 files it manages in your current directory.  So
  553 
  554 -------------------------------------
  555 $ git grep "hello"
  556 -------------------------------------
  557 
  558 is a quick way to search just the files that are tracked by Git.
  559 
  560 Many Git commands also take sets of commits, which can be specified
  561 in a number of ways.  Here are some examples with 'git log':
  562 
  563 -------------------------------------
  564 $ git log v2.5..v2.6            # commits between v2.5 and v2.6
  565 $ git log v2.5..                # commits since v2.5
  566 $ git log --since="2 weeks ago" # commits from the last 2 weeks
  567 $ git log v2.5.. Makefile       # commits since v2.5 which modify
  568 				# Makefile
  569 -------------------------------------
  570 
  571 You can also give 'git log' a "range" of commits where the first is not
  572 necessarily an ancestor of the second; for example, if the tips of
  573 the branches "stable" and "master" diverged from a common
  574 commit some time ago, then
  575 
  576 -------------------------------------
  577 $ git log stable..master
  578 -------------------------------------
  579 
  580 will list commits made in the master branch but not in the
  581 stable branch, while
  582 
  583 -------------------------------------
  584 $ git log master..stable
  585 -------------------------------------
  586 
  587 will show the list of commits made on the stable branch but not
  588 the master branch.
  589 
  590 The 'git log' command has a weakness: it must present commits in a
  591 list.  When the history has lines of development that diverged and
  592 then merged back together, the order in which 'git log' presents
  593 those commits is meaningless.
  594 
  595 Most projects with multiple contributors (such as the Linux kernel,
  596 or Git itself) have frequent merges, and 'gitk' does a better job of
  597 visualizing their history.  For example,
  598 
  599 -------------------------------------
  600 $ gitk --since="2 weeks ago" drivers/
  601 -------------------------------------
  602 
  603 allows you to browse any commits from the last 2 weeks of commits
  604 that modified files under the "drivers" directory.  (Note: you can
  605 adjust gitk's fonts by holding down the control key while pressing
  606 "-" or "+".)
  607 
  608 Finally, most commands that take filenames will optionally allow you
  609 to precede any filename by a commit, to specify a particular version
  610 of the file:
  611 
  612 -------------------------------------
  613 $ git diff v2.5:Makefile HEAD:Makefile.in
  614 -------------------------------------
  615 
  616 You can also use 'git show' to see any such file:
  617 
  618 -------------------------------------
  619 $ git show v2.5:Makefile
  620 -------------------------------------
  621 
  622 Next Steps
  623 ----------
  624 
  625 This tutorial should be enough to perform basic distributed revision
  626 control for your projects.  However, to fully understand the depth
  627 and power of Git you need to understand two simple ideas on which it
  628 is based:
  629 
  630   * The object database is the rather elegant system used to
  631     store the history of your project--files, directories, and
  632     commits.
  633 
  634   * The index file is a cache of the state of a directory tree,
  635     used to create commits, check out working directories, and
  636     hold the various trees involved in a merge.
  637 
  638 Part two of this tutorial explains the object
  639 database, the index file, and a few other odds and ends that you'll
  640 need to make the most of Git. You can find it at linkgit:gittutorial-2[7].
  641 
  642 If you don't want to continue with that right away, a few other
  643 digressions that may be interesting at this point are:
  644 
  645   * linkgit:git-format-patch[1], linkgit:git-am[1]: These convert
  646     series of git commits into emailed patches, and vice versa,
  647     useful for projects such as the Linux kernel which rely heavily
  648     on emailed patches.
  649 
  650   * linkgit:git-bisect[1]: When there is a regression in your
  651     project, one way to track down the bug is by searching through
  652     the history to find the exact commit that's to blame.  Git bisect
  653     can help you perform a binary search for that commit.  It is
  654     smart enough to perform a close-to-optimal search even in the
  655     case of complex non-linear history with lots of merged branches.
  656 
  657   * linkgit:gitworkflows[7]: Gives an overview of recommended
  658     workflows.
  659 
  660   * linkgit:giteveryday[7]: Everyday Git with 20 Commands Or So.
  661 
  662   * linkgit:gitcvs-migration[7]: Git for CVS users.
  663 
  664 SEE ALSO
  665 --------
  666 linkgit:gittutorial-2[7],
  667 linkgit:gitcvs-migration[7],
  668 linkgit:gitcore-tutorial[7],
  669 linkgit:gitglossary[7],
  670 linkgit:git-help[1],
  671 linkgit:gitworkflows[7],
  672 linkgit:giteveryday[7],
  673 link:user-manual.html[The Git User's Manual]
  674 
  675 GIT
  676 ---
  677 Part of the linkgit:git[1] suite