Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
tree: 4e6a83d28d
Fetching contributors…

Cannot retrieve contributors at this time

344 lines (293 sloc) 14.911 kb
---
layout: reference
---
<div class="box">
<h2>
<span class="docs">
<a target="new" href="http://progit.org/book/ch2-5.html">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://www.kernel.org/pub/software/scm/git/docs/git-remote.html">docs</a> &nbsp;
<a target="new" href="http://progit.org/book/ch2-5.html#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>
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:schacon/git-reference.git (fetch)
origin git@github.com:schacon/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>
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 elses 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 (I'll use 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 I've decided to name my remote 'github', but I could have really
named it just about anything.
</p>
<h4>
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>
<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 and <code>git remote rm</code> to delete existing ones.
</p>
</div>
</div>
<div class="box">
<h2>
<span class="docs">
<a target="new" href="http://www.kernel.org/pub/software/scm/git/docs/git-fetch.html">docs</a> &nbsp;
<a target="new" href="http://progit.org/book/ch2-5.html#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://www.kernel.org/pub/software/scm/git/docs/git-pull.html">docs</a> &nbsp;
<a target="new" href="http://progit.org/book/">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. I personally don't much
like this command - I prefer running <code>fetch</code> and <code>merge</code>
seperately. Less magic, less problems. However, if you like this idea, you
can read about it in more detail in the
<a target="new" href="http://www.kernel.org/pub/software/scm/git/docs/git-pull.html">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 I were working on my
Hello World project with several other people and I wanted to bring in any changes
that had been pushed since I last connected, I 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>I can see that since the last time I 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 this case, my team
is 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 now I can
merge the 'master' branch on that remote into my local 'master' branch by running
<code>git merge github/master</code>. Or, I 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 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://www.kernel.org/pub/software/scm/git/docs/git-push.html">docs</a> &nbsp;
<a target="new" href="http://progit.org/book/ch2-5.html#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 I have committed and all of its history.</p>
<p>What if I have a topic branch like the 'erlang' branch we created earlier
and I just want to share that? You can just push that branch instead.
<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 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>
<p><a href="/inspect">On to Inspection and Comparison &#187;</a></p>
Jump to Line
Something went wrong with that request. Please try again.