# gittutorial

## NAME



           gittutorial - A tutorial introduction to Git
    


## SYNOPSIS



           git *
    


## DESCRIPTION



           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 **The Git User’s Manual******[1].
    
           First, note that you can get documentation for a command such as**git log --graph** with:
    
               $ man git-log
    
           or:
    
               $ 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 user.name "Your Name Comes Here"
               $ git config --global user.email you@yourdomain.example.com
    


## IMPORTING A NEW PROJECT



           Assume you have a tarball **project.tar.gz** with your initial work.
           You can place it under Git revision control as follows.
    
               $ tar xzf project.tar.gz
               $ cd project
               $ git init
    
           Git will reply
    
               Initialized empty Git repository in .git/
    
           You’ve 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 add** :
    
               $ 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. You’ve now stored the
           first version of your project in Git.
    


## MAKING CHANGES



           Modify some files, then add their updated contents to the index:
    
               $ 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 you’ve
           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:
                 (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 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, it’s a good idea
           to begin the commit message with a single short (no more than 50
           characters) 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.
    


## GIT TRACKS CONTENT NOT FILES



           Many revision control systems provide an **add** command that tells
           the system to start tracking changes to a new file. Git’s **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.
    


## MANAGING BRANCHES



           A single Git repository can maintain multiple branches of
           development. To create a new branch named **experimental** , use
    
               $ git branch experimental
    
           If you now run
    
               $ git branch
    
           you’ll get a list of all existing branches:
    
                 experimental
               * 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 you’re 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
    
           If the changes don’t conflict, you’re done. If there are
           conflicts, markers will be left in the problematic files showing
           the conflict;
    
               $ git diff
    
           will show this. Once you’ve edited the files to resolve the
           conflicts,
    
               $ git commit -a
    
           will commit the result of the merge. Finally,
    
               $ gitk
    
           will show a nice graphical representation of the resulting
           history.
    
           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.
    


## USING GIT FOR COLLABORATION



           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 Alice’s
           repository. The clone is on an equal footing with the original
           project, possessing its own copy of the original project’s
           history.
    
           Bob then makes some changes and commits them:
    
               (edit files)
               bob$ git commit -a
               (repeat as necessary)
    
           When he’s 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 Bob’s **master** branch into Alice’s
           current branch. If Alice has made her own changes in the meantime,
           then she may need to manually fix any conflicts.
    
           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 Bob’s 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 happens).
    
           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:
    
               $ 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 form:
    
               $ gitk HEAD...FETCH_HEAD
    
           This means "show everything that is reachable from either one, but
           exclude anything that is reachable from both of them".
    
           Please note that these range notations 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 Bob’s
           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
           history.
    
           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 branched
           from Alice’s **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 Alice’s latest changes using
    
               bob$ git pull
    
           Note that he doesn’t need to give the path to Alice’s repository;
           when Bob cloned Alice’s 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
               /home/alice/project
    
           (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 Alice’s **master** branch under the
           name **origin/master** :
    
               bob$ git branch -r
                 origin/master
    
           If Bob later decides to work from a different host, he can still
           perform clones and pulls using the ssh protocol:
    
               bob$ git clone alice.org:/home/alice/project myrepo
    
           Alternatively, Git has a native protocol, or can use http; see
           git-pull(1) for details.
    
           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).
    


## NEXT STEPS



           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:
    
           •   The object database is the rather elegant system used to store
               the history of your project—files, directories, and commits.
    
           •   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 merge.
    
           Part two of this tutorial explains the object database, the index
           file, and a few other odds and ends that you’ll need to make the
           most of Git. You can find it at gittutorial-2(7).
    
           If you don’t want to continue with that right away, a few other
           digressions that may be interesting at this point are:
    
           •   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.
    
           •   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 that’s 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.
    
           •   gitworkflows(7): Gives an overview of recommended workflows.
    
           •   giteveryday(7): Everyday Git with 20 Commands Or So.
    
           •   gitcvs-migration(7): Git for CVS users.
    


## GIT



           Part of the git(1) suite
    


## NOTES



            1. The Git User’s Manual
               file:///home/mtk/share/doc/git-doc/user-manual.html
    


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