index.html

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layout: reference
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<div class="box">
  <h2>
    <span class="docs">
      <a target="new" href="http://git-scm.com/book/en/Git-Basics-Working-with-Remotes">book</a>
    </span>
    Sharing and Updating Projects
  </h2>
  <div class="block">
    <p>
    Git doesn't have a central server like Subversion.  All of the commands
    so far have been done locally, just updating a local database.
    To collaborate with other developers in Git, you have to put all that
    data on a server that the other developers have access to.  The way Git
    does this is to synchronize your data with another repository.  There
    is no real difference between a server and a client - a Git repository
    is a Git repository and you can synchronize between any two easily.
    </p>

    <p>Once you have a Git repository, either one that you set up on your
    own server, or one hosted someplace like GitHub, you can tell Git to
    either push any data that you have that is not in the remote repository
    up, or you can ask Git to fetch differences down from the other repo.
    </p>

    <p>You can do this any time you are online, it does not have to correspond
    with a <code>commit</code> or anything else.  Generally you will do a
    number of commits locally, then fetch data from the online shared repository
    you cloned the project from to get up to date, merge any new work into the
    stuff you did, then push your changes back up.</p>

    <p class="nutshell">
    <b>In a nutshell</b> you can update your project with <code>git fetch</code>
    and share your changes with <code>git push</code>. You can manage your
    remote repositories with <code>git remote</code>.
    </p>
  </div>
</div>

<div class="box">
  <h2>
    <span class="docs">
      <a target="new" href="http://git-scm.com/docs/git-remote">docs</a> &nbsp;
      <a target="new" href="http://git-scm.com/book/en/Git-Basics-Working-with-Remotes#Showing-Your-Remotes">book</a>
    </span>
    <a name="remote">git remote</a>
    <span class="desc">list, add and delete remote repository aliases</span>
  </h2>

  <div class="block">

    <p>Unlike centralized version control systems that have a client that is
    very different from a server, Git repositories are all basically equal and
    you simply synchronize between them. This makes it easy to have more than
    one remote repository - you can have some that you have read-only access to
    and others that you can write to as well.</p>

    <p>So that you don't have to use the full URL of a remote repository every
    time you want to synchronize with it, Git stores an alias or nickname for
    each remote repository URL you are interested in. You use the
    <code>git remote</code> command to manage this list of remote repos that
    you care about.</p>

    <h4 id="remote-list">
      git remote
      <small>list your remote aliases</small>
    </h4>

    <p>Without any arguments, Git will simply show you the remote repository
    aliases that it has stored. By default, if you cloned the project (as
    opposed to creating a new one locally), Git will automatically add the
    URL of the repository that you cloned from under the name 'origin'. If
    you run the command with the <code>-v</code> option, you can see the
    actual URL for each alias.</p>

<pre>
<b>$ git remote</b>
origin
<b>$ git remote -v</b>
origin	git@github.com:github/git-reference.git (fetch)
origin	git@github.com:github/git-reference.git (push)
</pre>

    <p>You see the URL there twice because Git allows you to have different
    push and fetch URLs for each remote in case you want to use different
    protocols for reads and writes.</p>

    <h4 id="remote-add">
      git remote add
      <small>add a new remote repository of your project</small>
    </h4>

    <p>If you want to share a locally created repository, or you want to take
    contributions from someone else's repository - if you want to interact in
    any way with a new repository, it's generally easiest to add it as a remote.
    You do that by running <code>git remote add [alias] [url]</code>.  That
    adds <code>[url]</code> under a local remote named <code>[alias]</code>.</p>

    <p>For example, if we want to share our Hello World program with the world,
    we can create a new repository on a server (Using GitHub as an example),
    which should give you a URL, in this case "git@github.com:schacon/hw.git".
    To add that to our project so we can push to it and fetch updates from it
    we would do this:</p>

<pre>
<b>$ git remote</b>
<b>$ git remote add github git@github.com:schacon/hw.git</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
</pre>

    <p>Like the branch naming, remote alias names are arbitrary - just as 'master'
    has no special meaning but is widely used because <code>git init</code>
    sets it up by default, 'origin' is often used as a remote name because
    <code>git clone</code> sets it up by default as the cloned-from URL. In
    this case we'll name the remote 'github', but you could name it just
    about anything.
    </p>

    <h4 id="remote-remove">
      git remote rm
      <small>removing an existing remote alias</small>
    </h4>

    <p>Git addeth and Git taketh away.  If you need to remove a remote - you are
    not using it anymore, the project is gone, etc - you can remove it with
    <code>git remote rm [alias]</code>.</p>

<pre>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
<b>$ git remote add origin git://github.com/pjhyett/hw.git</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/pjhyett/hw.git (fetch)
origin	git://github.com/pjhyett/hw.git (push)
<b>$ git remote rm origin</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
</pre>

	<h4 id="remote-rename">
      git remote rename [old-alias] [new-alias]
      <small>rename remote aliases</small>
    </h4>

    <p>If you want to rename remote aliases without having to delete them and add them again
    you can do that by running <code>git remote rename [old-alias] [new-alias]</code>. This will
    allow you to modify the current name of the remote.</p>

<pre>
<b>$ git remote add github git@github.com:schacon/hw.git</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
<b>$ git remote rename github origin</b>
<b>$ git remote -v</b>
origin	git@github.com:schacon/hw.git (fetch)
origin	git@github.com:schacon/hw.git (push)
</pre>

    <p class="nutshell">
    <b>In a nutshell</b> with <code>git remote</code> you can list our
    remote repositories and whatever URL
    that repository is using.  You can use <code>git remote add</code> to
    add new remotes, <code>git remote rm</code> to delete existing ones or <code>git remote rename [old-alias] [new-alias]</code> to rename them.
    </p>

    <h4 id="remote-update">
      git remote set-url
      <small>update an existing remote URL</small>
    </h4>

    <p>Should you ever need to update a remote's URL, you can do so with
    the <code>git remote set-url</code> command.
    </p>

<pre>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/pjhyett/hw.git (fetch)
origin	git://github.com/pjhyett/hw.git (push)
<b>$ git remote set-url origin git://github.com/github/git-reference.git</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/github/git-reference.git (fetch)
origin	git://github.com/github/git-reference.git (push)
</pre>

    <p>In addition to this, you can set a different push URL when you
    include the <code>--push</code> flag. This allows you to fetch from
    one repo while pushing to another and yet both use the same remote alias.
    </p>

<pre>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/github/git-reference.git (fetch)
origin	git://github.com/github/git-reference.git (push)
<b>$ git remote set-url --push origin git://github.com/pjhyett/hw.git</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/github/git-reference.git (fetch)
origin	git://github.com/pjhyett/hw.git (push)
</pre>

    <p>Internally, the <code>git remote set-url</code> command calls
    <code>git config remote</code>, but has the added benefit of reporting
    back any errors. <code>git config remote</code> on the other hand, will
    silently fail if you mistype an argument or option and not actually set
    anything.
    </p>

    <p>For example, we'll update the <code>github</code> remote but
    instead reference it as <code>guhflub</code> in both invocations.
    </p>

<pre>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/github/git-reference.git (fetch)
origin	git://github.com/github/git-reference.git (push)
<b>$ git config remote.guhflub git://github.com/mojombo/hw.git</b>
<b>$ git remote -v</b>
github	git@github.com:schacon/hw.git (fetch)
github	git@github.com:schacon/hw.git (push)
origin	git://github.com/github/git-reference.git (fetch)
origin	git://github.com/github/git-reference.git (push)
<b>$ git remote set-url guhflub git://github.com/mojombo/hw.git</b>
fatal: No such remote 'guhflub'
</pre>

    <p class="nutshell">
    <b>In a nutshell</b>, you can update the locations of your remotes
    with <code>git remote set-url</code>. You can also set different push
    and fetch URLs under the same remote alias.
    </p>

  </div>
</div>

<div class="box">
  <h2>
    <span class="docs">
      <a target="new" href="http://git-scm.com/docs/git-fetch">docs</a> &nbsp;
      <a target="new" href="http://git-scm.com/book/en/Git-Basics-Working-with-Remotes#Fetching-and-Pulling-from-Your-Remotes">book</a>
    </span>
    <a name="fetch">git fetch</a>
    <span class="desc">download new branches and data from a remote repository</span>
  </h2>

  <br/>

  <h2>
    <span class="docs">
      <a target="new" href="http://git-scm.com/docs/git-pull">docs</a> &nbsp;
      <a target="new" href="http://git-scm.com/book/en/Git-Basics-Working-with-Remotes#Fetching-and-Pulling-from-Your-Remotes">book</a>
    </span>
    <a name="pull">git pull</a>
    <span class="desc">fetch from a remote repo and try to merge into the current branch</span>
  </h2>

  <div class="block">

    <p>Git has two commands to update itself from a remote repository.
    <code>git fetch</code> will synchronize you with another repo, pulling down any data
    that you do not have locally and giving you bookmarks to where each branch on
    that remote was when you synchronized.  These are called "remote branches" and are
    identical to local branches except that Git will not allow you to check them out -
    however, you can merge from them, diff them to other branches, run history logs on
    them, etc.  You do all of that stuff locally after you synchronize.
    </p>

    <p>The second command that will fetch down new data from a remote server is
    <code>git pull</code>.  This command will basically run a <code>git fetch</code>
    immediately followed by a <code>git merge</code> of the branch on that remote
    that is tracked by whatever branch you are currently in.  Running the
    <code>fetch</code> and <code>merge</code> commands separately involves less magic
    and less problems, but if you like the idea of <code>pull</code>, you can
    read about it in more detail in the
    <a target="new" href="http://git-scm.com/docs/git-pull">official docs</a>.
    </p>

    <p>Assuming you have a remote all set up and you want to pull in updates, you
    would first run <code>git fetch [alias]</code> to tell Git to fetch down all the
    data it has that you do not, then you would run <code>git merge [alias]/[branch]</code>
    to merge into your current branch anything new you see on the server
    (like if someone else has pushed in the meantime). So, if you were working on a
    Hello World project with several other people and wanted to bring in any changes
    that had been pushed since we last connected, we would do something like this:</p>

<pre>
<b>$ git fetch github</b>
remote: Counting objects: 4006, done.
remote: Compressing objects: 100% (1322/1322), done.
remote: Total 2783 (delta 1526), reused 2587 (delta 1387)
Receiving objects: 100% (2783/2783), 1.23 MiB | 10 KiB/s, done.
Resolving deltas: 100% (1526/1526), completed with 387 local objects.
From github.com:schacon/hw
   8e29b09..c7c5a10  master     -> github/master
   0709fdc..d4ccf73  c-langs    -> github/c-langs
   6684f82..ae06d2b  java       -> github/java
 * [new branch]      ada        -> github/ada
 * [new branch]      lisp       -> github/lisp
</pre>

    <p>Here we can see that since we last synchronized with this remote, five branches
    have been added or updated.  The 'ada' and 'lisp' branches are new, where the
    'master', 'c-langs' and 'java' branches have been updated.  In our example case,
    other developers are pushing proposed updates to remote branches for review before
    they're merged into 'master'.
    </p>

    <p>You can see the mapping that Git makes.  The 'master' branch on the remote
    repository becomes a branch named 'github/master' locally.  That way you can
    merge the 'master' branch on that remote into the local 'master' branch by running
    <code>git merge github/master</code>.  Or, you can see what new commits are on that
    branch by running <code>git log github/master ^master</code>.  If your remote
    is named 'origin' it would be <code>origin/master</code> instead.  Almost any
    command you would run using local branches you can use remote branches with too.
    </p>

    <p>If you have more than one remote repository, you can either fetch from specific
    ones by running <code>git fetch [alias]</code> or you can tell Git to synchronize
    with all of your remotes by running <code>git fetch --all</code>.
	</p>

    <p class="nutshell">
    <b>In a nutshell</b> you run <code>git fetch [alias]</code> to synchronize your
    repository with a remote repository, fetching all the data it has that you do
    not into branch references locally for merging and whatnot.
    </p>

  </div>

</div>

<div class="box">
  <h2>
    <span class="docs">
      <a target="new" href="http://git-scm.com/docs/git-push">docs</a> &nbsp;
      <a target="new" href="http://git-scm.com/book/en/Git-Basics-Working-with-Remotes#Pushing-to-Your-Remotes">book</a>
    </span>
    <a name="push">git push</a>
    <span class="desc">push your new branches and data to a remote repository</span>
  </h2>

  <div class="block">
    <p>To share the cool commits you've done with others, you need to push your
    changes to the remote repository. To do this, you run
    <code>git push [alias] [branch]</code> which will attempt to make your [branch]
    the new [branch] on the [alias] remote. Let's try it by initially pushing
    our 'master' branch to the new 'github' remote we created earlier.</p>

<pre>
<b>$ git push github master</b>
Counting objects: 25, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (25/25), done.
Writing objects: 100% (25/25), 2.43 KiB, done.
Total 25 (delta 4), reused 0 (delta 0)
To git@github.com:schacon/hw.git
 * [new branch]      master -> master
</pre>

    <p>Pretty easy. Now if someone clones that repository they will get exactly
    what we have committed and all of its history.</p>

    <p>What if you have a topic branch like the 'erlang' branch created earlier
    and want to share just that?  You can just push that branch instead.</p>

<pre>
<b>$ git push github erlang</b>
Counting objects: 7, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (6/6), done.
Writing objects: 100% (6/6), 652 bytes, done.
Total 6 (delta 1), reused 0 (delta 0)
To git@github.com:schacon/hw.git
 * [new branch]      erlang -> erlang
</pre>

    <p>Now when people clone or fetch from that repository, they'll get an 'erlang'
    branch they can look at and merge from. You can push any branch to any
    remote repository that you have write access to in this way. If your branch
    is already on the server, it will try to update it, if it is not, Git will
    add it.</p>

    <p>The last major issue you run into with pushing to remote branches is the
    case of someone pushing in the meantime.  If you and another developer clone
    at the same time, you both do commits, then she pushes and then you try to
    push, Git will by default not allow you to overwrite her changes.  Instead,
    it basically runs <code>git log</code> on the branch you're trying to push and
    makes sure it can see the current tip of the server's branch in your push's
    history.  If it can't see what is on the server in your history, it concludes
    that you are out of date and will reject your push.  You will rightly have to
    fetch, merge then push again - which makes sure you take her changes into
    account.</p>

    <p>This is what happens when you try to push a branch to a remote branch
    that has been updated in the meantime:</p>

<pre>
<b>$ git push github master</b>
To git@github.com:schacon/hw.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'git@github.com:schacon/hw.git'
To prevent you from losing history, non-fast-forward updates were rejected
Merge the remote changes before pushing again.  See the 'Note about
fast-forwards' section of 'git push --help' for details.
</pre>

    <p>You can fix this by running <code>git fetch github; git merge github/master</code>
    and then pushing again.
	</p>

    <p class="nutshell">
    <b>In a nutshell</b> you run <code>git push [alias] [branch]</code> to update a
    remote repository with the changes you've made locally.  It will take what your
    [branch] looks like and push it to be [branch] on the remote, if possible.  If
    someone else has pushed since you last fetched and merged, the Git server will
    deny your push until you are up to date.
    </p>

  </div>
</div>

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