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          gittutorial - A tutorial introduction to Git

          git *

          This tutorial explains how to import a new project into Git,
          make changes to it, and share changes with other developers.

          If you are instead primarily interested in using Git to
          fetch a project, for example, to test the latest version,
          you may prefer to start with the first two chapters of
          m[blue]The Git Usercqs Manualm[][1].

          First, note that you can get documentation for a command
          such as git log --graph with:

              $ man git-log


              $ git help log

          With the latter, you can use the manual viewer of your
          choice; see git-help(1) for more information.

          It is a good idea to introduce yourself to Git with your
          name and public email address before doing any operation.
          The easiest way to do so is:

              $ git config --global "Your Name Comes Here"
              $ git config --global

          Assume you have a tarball project.tar.gz with your initial
          work. You can place it under Git revision control as

              $ tar xzf project.tar.gz
              $ cd project
              $ git init

          Git will reply

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              Initialized empty Git repository in .git/

          Youcqve now initialized the working directory-you may notice
          a new directory created, named ".git".

          Next, tell Git to take a snapshot of the contents of all
          files under the current directory (note the .), with git

              $ git add .

          This snapshot is now stored in a temporary staging area
          which Git calls the "index". You can permanently store the
          contents of the index in the repository with git commit:

              $ git commit

          This will prompt you for a commit message. Youcqve now stored
          the first version of your project in Git.

          Modify some files, then add their updated contents to the

              $ git add file1 file2 file3

          You are now ready to commit. You can see what is about to be
          committed using git diff with the --cached option:

              $ git diff --cached

          (Without --cached, git diff will show you any changes that
          youcqve made but not yet added to the index.) You can also
          get a brief summary of the situation with git status:

              $ git status
              On branch master
              Changes to be committed:
              Your branch is up to date with 'origin/master'.
                (use "git restore --staged <file>..." to unstage)

                      modified:   file1
                      modified:   file2
                      modified:   file3

          If you need to make any further adjustments, do so now, and

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          then add any newly modified content to the index. Finally,
          commit your changes with:

              $ git commit

          This will again prompt you for a message describing the
          change, and then record a new version of the project.

          Alternatively, instead of running git add beforehand, you
          can use

              $ git commit -a

          which will automatically notice any modified (but not new)
          files, add them to the index, and commit, all in one step.

          A note on commit messages: Though not required, itcqs a good
          idea to begin the commit message with a single short (less
          than 50 character) line summarizing the change, followed by
          a blank line and then a more thorough description. The text
          up to the first blank line in a commit message is treated as
          the commit title, and that title is used throughout Git. For
          example, git-format-patch(1) turns a commit into email, and
          it uses the title on the Subject line and the rest of the
          commit in the body.

          Many revision control systems provide an add command that
          tells the system to start tracking changes to a new file.
          Gitcqs add command does something simpler and more powerful:
          git add is used both for new and newly modified files, and
          in both cases it takes a snapshot of the given files and
          stages that content in the index, ready for inclusion in the
          next commit.

          At any point you can view the history of your changes using

              $ git log

          If you also want to see complete diffs at each step, use

              $ git log -p

          Often the overview of the change is useful to get a feel of
          each step

              $ git log --stat --summary

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          A single Git repository can maintain multiple branches of
          development. To create a new branch named "experimental",

              $ git branch experimental

          If you now run

              $ git branch

          youcqll get a list of all existing branches:

              * master

          The "experimental" branch is the one you just created, and
          the "master" branch is a default branch that was created for
          you automatically. The asterisk marks the branch you are
          currently on; type

              $ git switch experimental

          to switch to the experimental branch. Now edit a file,
          commit the change, and switch back to the master branch:

              (edit file)
              $ git commit -a
              $ git switch master

          Check that the change you made is no longer visible, since
          it was made on the experimental branch and youcqre back on
          the master branch.

          You can make a different change on the master branch:

              (edit file)
              $ git commit -a

          at this point the two branches have diverged, with different
          changes made in each. To merge the changes made in
          experimental into master, run

              $ git merge experimental

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          If the changes doncqt conflict, youcqre done. If there are
          conflicts, markers will be left in the problematic files
          showing the conflict;

              $ git diff

          will show this. Once youcqve edited the files to resolve the

              $ git commit -a

          will commit the result of the merge. Finally,

              $ gitk

          will show a nice graphical representation of the resulting

          At this point you could delete the experimental branch with

              $ git branch -d experimental

          This command ensures that the changes in the experimental
          branch are already in the current branch.

          If you develop on a branch crazy-idea, then regret it, you
          can always delete the branch with

              $ git branch -D crazy-idea

          Branches are cheap and easy, so this is a good way to try
          something out.

          Suppose that Alice has started a new project with a Git
          repository in /home/alice/project, and that Bob, who has a
          home directory on the same machine, wants to contribute.

          Bob begins with:

              bob$ git clone /home/alice/project myrepo

          This creates a new directory "myrepo" containing a clone of
          Alicecqs repository. The clone is on an equal footing with
          the original project, possessing its own copy of the
          original projectcqs history.

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          Bob then makes some changes and commits them:

              (edit files)
              bob$ git commit -a
              (repeat as necessary)

          When hecqs ready, he tells Alice to pull changes from the
          repository at /home/bob/myrepo. She does this with:

              alice$ cd /home/alice/project
              alice$ git pull /home/bob/myrepo master

          This merges the changes from Bobcqs "master" branch into
          Alicecqs current branch. If Alice has made her own changes in
          the meantime, then she may need to manually fix any

          The "pull" command thus performs two operations: it fetches
          changes from a remote branch, then merges them into the
          current branch.

          Note that in general, Alice would want her local changes
          committed before initiating this "pull". If Bobcqs work
          conflicts with what Alice did since their histories forked,
          Alice will use her working tree and the index to resolve
          conflicts, and existing local changes will interfere with
          the conflict resolution process (Git will still perform the
          fetch but will refuse to merge - Alice will have to get rid
          of her local changes in some way and pull again when this

          Alice can peek at what Bob did without merging first, using
          the "fetch" command; this allows Alice to inspect what Bob
          did, using a special symbol "FETCH_HEAD", in order to
          determine if he has anything worth pulling, like this:

              alice$ git fetch /home/bob/myrepo master
              alice$ git log -p HEAD..FETCH_HEAD

          This operation is safe even if Alice has uncommitted local
          changes. The range notation "HEAD..FETCH_HEAD" means "show
          everything that is reachable from the FETCH_HEAD but exclude
          anything that is reachable from HEAD". Alice already knows
          everything that leads to her current state (HEAD), and
          reviews what Bob has in his state (FETCH_HEAD) that she has
          not seen with this command.

          If Alice wants to visualize what Bob did since their
          histories forked she can issue the following command:

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              $ gitk HEAD..FETCH_HEAD

          This uses the same two-dot range notation we saw earlier
          with git log.

          Alice may want to view what both of them did since they
          forked. She can use three-dot form instead of the two-dot

              $ gitk HEAD...FETCH_HEAD

          This means "show everything that is reachable from either
          one, but exclude anything that is reachable from both of

          Please note that these range notation can be used with both
          gitk and "git log".

          After inspecting what Bob did, if there is nothing urgent,
          Alice may decide to continue working without pulling from
          Bob. If Bobcqs history does have something Alice would
          immediately need, Alice may choose to stash her
          work-in-progress first, do a "pull", and then finally
          unstash her work-in-progress on top of the resulting

          When you are working in a small closely knit group, it is
          not unusual to interact with the same repository over and
          over again. By defining remote repository shorthand, you can
          make it easier:

              alice$ git remote add bob /home/bob/myrepo

          With this, Alice can perform the first part of the "pull"
          operation alone using the git fetch command without merging
          them with her own branch, using:

              alice$ git fetch bob

          Unlike the longhand form, when Alice fetches from Bob using
          a remote repository shorthand set up with git remote, what
          was fetched is stored in a remote-tracking branch, in this
          case bob/master. So after this:

              alice$ git log -p master..bob/master

          shows a list of all the changes that Bob made since he

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          branched from Alicecqs master branch.

          After examining those changes, Alice could merge the changes
          into her master branch:

              alice$ git merge bob/master

          This merge can also be done by pulling from her own
          remote-tracking branch, like this:

              alice$ git pull . remotes/bob/master

          Note that git pull always merges into the current branch,
          regardless of what else is given on the command line.

          Later, Bob can update his repo with Alicecqs latest changes

              bob$ git pull

          Note that he doesncqt need to give the path to Alicecqs
          repository; when Bob cloned Alicecqs repository, Git stored
          the location of her repository in the repository
          configuration, and that location is used for pulls:

              bob$ git config --get remote.origin.url

          (The complete configuration created by git clone is visible
          using git config -l, and the git-config(1) man page explains
          the meaning of each option.)

          Git also keeps a pristine copy of Alicecqs master branch
          under the name "origin/master":

              bob$ git branch -r

          If Bob later decides to work from a different host, he can
          still perform clones and pulls using the ssh protocol:

              bob$ git clone myrepo

          Alternatively, Git has a native protocol, or can use http;
          see git-pull(1) for details.

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          Git can also be used in a CVS-like mode, with a central
          repository that various users push changes to; see git-
          push(1) and gitcvs-migration(7).

          Git history is represented as a series of interrelated
          commits. We have already seen that the git log command can
          list those commits. Note that first line of each git log
          entry also gives a name for the commit:

              $ git log
              commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
              Author: Junio C Hamano <>
              Date:   Tue May 16 17:18:22 2006 -0700

                  merge-base: Clarify the comments on post processing.

          We can give this name to git show to see the details about
          this commit.

              $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7

          But there are other ways to refer to commits. You can use
          any initial part of the name that is long enough to uniquely
          identify the commit:

              $ git show c82a22c39c   # the first few characters of the name are
                                      # usually enough
              $ git show HEAD         # the tip of the current branch
              $ git show experimental # the tip of the "experimental" branch

          Every commit usually has one "parent" commit which points to
          the previous state of the project:

              $ git show HEAD^  # to see the parent of HEAD
              $ git show HEAD^^ # to see the grandparent of HEAD
              $ git show HEAD~4 # to see the great-great grandparent of HEAD

          Note that merge commits may have more than one parent:

              $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
              $ git show HEAD^2 # show the second parent of HEAD

          You can also give commits names of your own; after running

              $ git tag v2.5 1b2e1d63ff

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          you can refer to 1b2e1d63ff by the name "v2.5". If you
          intend to share this name with other people (for example, to
          identify a release version), you should create a "tag"
          object, and perhaps sign it; see git-tag(1) for details.

          Any Git command that needs to know a commit can take any of
          these names. For example:

              $ git diff v2.5 HEAD     # compare the current HEAD to v2.5
              $ git branch stable v2.5 # start a new branch named "stable" based
                                       # at v2.5
              $ git reset --hard HEAD^ # reset your current branch and working
                                       # directory to its state at HEAD^

          Be careful with that last command: in addition to losing any
          changes in the working directory, it will also remove all
          later commits from this branch. If this branch is the only
          branch containing those commits, they will be lost. Also,
          doncqt use git reset on a publicly-visible branch that other
          developers pull from, as it will force needless merges on
          other developers to clean up the history. If you need to
          undo changes that you have pushed, use git revert instead.

          The git grep command can search for strings in any version
          of your project, so

              $ git grep "hello" v2.5

          searches for all occurrences of "hello" in v2.5.

          If you leave out the commit name, git grep will search any
          of the files it manages in your current directory. So

              $ git grep "hello"

          is a quick way to search just the files that are tracked by

          Many Git commands also take sets of commits, which can be
          specified in a number of ways. Here are some examples with
          git log:

              $ git log v2.5..v2.6            # commits between v2.5 and v2.6
              $ git log v2.5..                # commits since v2.5
              $ git log --since="2 weeks ago" # commits from the last 2 weeks
              $ git log v2.5.. Makefile       # commits since v2.5 which modify
                                              # Makefile

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          You can also give git log a "range" of commits where the
          first is not necessarily an ancestor of the second; for
          example, if the tips of the branches "stable" and "master"
          diverged from a common commit some time ago, then

              $ git log stable..master

          will list commits made in the master branch but not in the
          stable branch, while

              $ git log master..stable

          will show the list of commits made on the stable branch but
          not the master branch.

          The git log command has a weakness: it must present commits
          in a list. When the history has lines of development that
          diverged and then merged back together, the order in which
          git log presents those commits is meaningless.

          Most projects with multiple contributors (such as the Linux
          kernel, or Git itself) have frequent merges, and gitk does a
          better job of visualizing their history. For example,

              $ gitk --since="2 weeks ago" drivers/

          allows you to browse any commits from the last 2 weeks of
          commits that modified files under the "drivers" directory.
          (Note: you can adjust gitkcqs fonts by holding down the
          control key while pressing "-" or "+".)

          Finally, most commands that take filenames will optionally
          allow you to precede any filename by a commit, to specify a
          particular version of the file:

              $ git diff v2.5:Makefile

          You can also use git show to see any such file:

              $ git show v2.5:Makefile

          This tutorial should be enough to perform basic distributed
          revision control for your projects. However, to fully
          understand the depth and power of Git you need to understand
          two simple ideas on which it is based:

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          +o   The object database is the rather elegant system used to
              store the history of your project-files, directories,
              and commits.

          +o   The index file is a cache of the state of a directory
              tree, used to create commits, check out working
              directories, and hold the various trees involved in a

          Part two of this tutorial explains the object database, the
          index file, and a few other odds and ends that youcqll need
          to make the most of Git. You can find it at gittutorial-

          If you doncqt want to continue with that right away, a few
          other digressions that may be interesting at this point are:

          +o   git-format-patch(1), git-am(1): These convert series of
              git commits into emailed patches, and vice versa, useful
              for projects such as the Linux kernel which rely heavily
              on emailed patches.

          +o   git-bisect(1): When there is a regression in your
              project, one way to track down the bug is by searching
              through the history to find the exact commit thatcqs to
              blame. Git bisect can help you perform a binary search
              for that commit. It is smart enough to perform a
              close-to-optimal search even in the case of complex
              non-linear history with lots of merged branches.

          +o   gitworkflows(7): Gives an overview of recommended

          +o   giteveryday(7): Everyday Git with 20 Commands Or So.

          +o   gitcvs-migration(7): Git for CVS users.

          gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
          gitglossary(7), git-help(1), gitworkflows(7),
          giteveryday(7), m[blue]The Git Usercqs Manualm[][1]

          Part of the git(1) suite

           1. The Git Usercqs Manual

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