[[_remote_branches]]
=== Remote Branches

(((branches, remote)))(((references, remote)))
Remote references are references (pointers) in your remote repositories, including branches, tags, and so on.
You can get a full list of remote references explicitly with `git ls-remote <remote>`, or `git remote show <remote>` for remote branches as well as more information.
Nevertheless, a more common way is to take advantage of remote-tracking branches.

Remote-tracking branches are references to the state of remote branches.
They're local references that you can't move; Git moves them for you whenever you do any network communication, to make sure they accurately represent the state of the remote repository.
Think of them as bookmarks, to remind you where the branches in your remote repositories were the last time you connected to them.

Remote-tracking branch names take the form `<remote>/<branch>`.
For instance, if you wanted to see what the `master` branch on your `origin` remote looked like as of the last time you communicated with it, you would check the `origin/master` branch.
If you were working on an issue with a partner and they pushed up an `iss53` branch, you might have your own local `iss53` branch, but the branch on the server would be represented by the remote-tracking branch `origin/iss53`.

This may be a bit confusing, so let's look at an example.
Let's say you have a Git server on your network at `git.ourcompany.com`.
If you clone from this, Git's `clone` command automatically names it `origin` for you, pulls down all its data, creates a pointer to where its `master` branch is, and names it `origin/master` locally.
Git also gives you your own local `master` branch starting at the same place as origin's `master` branch, so you have something to work from.

[NOTE]
."`origin`" is not special
====
Just like the branch name "`master`" does not have any special meaning in Git, neither does "`origin`".
While "`master`" is the default name for a starting branch when you run `git init` which is the only reason it's widely used, "`origin`" is the default name for a remote when you run `git clone`.
If you run `git clone -o booyah` instead, then you will have `booyah/master` as your default remote branch.(((origin)))
====

.Server and local repositories after cloning
image::images/remote-branches-1.png[Server and local repositories after cloning]

If you do some work on your local `master` branch, and, in the meantime, someone else pushes to `git.ourcompany.com` and updates its `master` branch, then your histories move forward differently.
Also, as long as you stay out of contact with your `origin` server, your `origin/master` pointer doesn't move.

.Local and remote work can diverge
image::images/remote-branches-2.png[Local and remote work can diverge]

To synchronize your work with a given remote, you run a `git fetch <remote>` command (in our case, `git fetch origin`).
This command looks up which server "`origin`" is (in this case, it's `git.ourcompany.com`), fetches any data from it that you don't yet have, and updates your local database, moving your `origin/master` pointer to its new, more up-to-date position.

.`git fetch` updates your remote-tracking branches
image::images/remote-branches-3.png[`git fetch` updates your remote-tracking branches]

To demonstrate having multiple remote servers and what remote branches for those remote projects look like, let's assume you have another internal Git server that is used only for development by one of your sprint teams.
This server is at `git.team1.ourcompany.com`.
You can add it as a new remote reference to the project you're currently working on by running the `git remote add` command as we covered in <<ch02-git-basics-chapter#ch02-git-basics-chapter>>.
Name this remote `teamone`, which will be your shortname for that whole URL.

.Adding another server as a remote
image::images/remote-branches-4.png[Adding another server as a remote]

Now, you can run `git fetch teamone` to fetch everything the remote `teamone` server has that you don't have yet.
Because that server has a subset of the data your `origin` server has right now, Git fetches no data but sets a remote-tracking branch called `teamone/master` to point to the commit that `teamone` has as its `master` branch.

.Remote-tracking branch for `teamone/master`
image::images/remote-branches-5.png[Remote-tracking branch for `teamone/master`]

[[_pushing_branches]]
==== Pushing

(((pushing)))
When you want to share a branch with the world, you need to push it up to a remote to which you have write access.
Your local branches aren't automatically synchronized to the remotes you write to -- you have to explicitly push the branches you want to share.
That way, you can use private branches for work you don't want to share, and push up only the topic branches you want to collaborate on.

If you have a branch named `serverfix` that you want to work on with others, you can push it up the same way you pushed your first branch.
Run `git push <remote> <branch>`:(((git commands, push)))

[source,console]
----
$ git push origin serverfix
Counting objects: 24, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (15/15), done.
Writing objects: 100% (24/24), 1.91 KiB | 0 bytes/s, done.
Total 24 (delta 2), reused 0 (delta 0)
To https://github.com/schacon/simplegit
 * [new branch]      serverfix -> serverfix
----

This is a bit of a shortcut.
Git automatically expands the `serverfix` branchname out to `refs/heads/serverfix:refs/heads/serverfix`, which means, "`Take my `serverfix` local branch and push it to update the remote's `serverfix` branch.`"
We'll go over the `refs/heads/` part in detail in <<ch10-git-internals#ch10-git-internals>>, but you can generally leave it off.
You can also do `git push origin serverfix:serverfix`, which does the same thing -- it says, "`Take my serverfix and make it the remote's serverfix.`"
You can use this format to push a local branch into a remote branch that is named differently.
If you didn't want it to be called `serverfix` on the remote, you could instead run `git push origin serverfix:awesomebranch` to push your local `serverfix` branch to the `awesomebranch` branch on the remote project.

[NOTE]
.Don't type your password every time
====
If you're using an HTTPS URL to push over, the Git server will ask you for your username and password for authentication.
By default it will prompt you on the terminal for this information so the server can tell if you're allowed to push.

If you don't want to type it every single time you push, you can set up a "`credential cache`".
The simplest is just to keep it in memory for a few minutes, which you can easily set up by running `git config --global credential.helper cache`.

For more information on the various credential caching options available, see <<ch07-git-tools#_credential_caching>>.
====

The next time one of your collaborators fetches from the server, they will get a reference to where the server's version of `serverfix` is under the remote branch `origin/serverfix`:

[source,console]
----
$ git fetch origin
remote: Counting objects: 7, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 3 (delta 0), reused 3 (delta 0)
Unpacking objects: 100% (3/3), done.
From https://github.com/schacon/simplegit
 * [new branch]      serverfix    -> origin/serverfix
----

It's important to note that when you do a fetch that brings down new remote-tracking branches, you don't automatically have local, editable copies of them.
In other words, in this case, you don't have a new `serverfix` branch -- you have only an `origin/serverfix` pointer that you can't modify.

To merge this work into your current working branch, you can run `git merge origin/serverfix`.
If you want your own `serverfix` branch that you can work on, you can base it off your remote-tracking branch:

[source,console]
----
$ git checkout -b serverfix origin/serverfix
Branch serverfix set up to track remote branch serverfix from origin.
Switched to a new branch 'serverfix'
----

This gives you a local branch that you can work on that starts where `origin/serverfix` is.

[[_tracking_branches]]
==== Tracking Branches

(((branches, tracking)))(((branches, upstream)))
Checking out a local branch from a remote-tracking branch automatically creates what is called a "`tracking branch`" (and the branch it tracks is called an "`upstream branch`").
Tracking branches are local branches that have a direct relationship to a remote branch.
If you're on a tracking branch and type `git pull`, Git automatically knows which server to fetch from and which branch to merge in.

When you clone a repository, it generally automatically creates a `master` branch that tracks `origin/master`.
However, you can set up other tracking branches if you wish -- ones that track branches on other remotes, or don't track the `master` branch.
The simple case is the example you just saw, running `git checkout -b <branch> <remote>/<branch>`.
This is a common enough operation that Git provides the `--track` shorthand:

[source,console]
----
$ git checkout --track origin/serverfix
Branch serverfix set up to track remote branch serverfix from origin.
Switched to a new branch 'serverfix'
----

In fact, this is so common that there's even a shortcut for that shortcut.
If the branch name you're trying to checkout (a) doesn't exist and (b) exactly matches a name on only one remote, Git will create a tracking branch for you:

[source,console]
----
$ git checkout serverfix
Branch serverfix set up to track remote branch serverfix from origin.
Switched to a new branch 'serverfix'
----

To set up a local branch with a different name than the remote branch, you can easily use the first version with a different local branch name:

[source,console]
----
$ git checkout -b sf origin/serverfix
Branch sf set up to track remote branch serverfix from origin.
Switched to a new branch 'sf'
----

Now, your local branch `sf` will automatically pull from `origin/serverfix`.

If you already have a local branch and want to set it to a remote branch you just pulled down, or want to change the upstream branch you're tracking, you can use the `-u` or `--set-upstream-to` option to `git branch` to explicitly set it at any time.

[source,console]
----
$ git branch -u origin/serverfix
Branch serverfix set up to track remote branch serverfix from origin.
----

[NOTE]
.Upstream shorthand
====
When you have a tracking branch set up, you can reference its upstream branch with the `@{upstream}` or `@{u}` shorthand.
So if you're on the `master` branch and it's tracking `origin/master`, you can say something like `git merge @{u}` instead of `git merge origin/master` if you wish.(((@{u})))(((@{upstream})))
====

If you want to see what tracking branches you have set up, you can use the `-vv` option to `git branch`.
This will list out your local branches with more information including what each branch is tracking and if your local branch is ahead, behind or both.

[source,console]
----
$ git branch -vv
  iss53     7e424c3 [origin/iss53: ahead 2] Add forgotten brackets
  master    1ae2a45 [origin/master] Deploy index fix
* serverfix f8674d9 [teamone/server-fix-good: ahead 3, behind 1] This should do it
  testing   5ea463a Try something new
----

So here we can see that our `iss53` branch is tracking `origin/iss53` and is "`ahead`" by two, meaning that we have two commits locally that are not pushed to the server.
We can also see that our `master` branch is tracking `origin/master` and is up to date.
Next we can see that our `serverfix` branch is tracking the `server-fix-good` branch on our `teamone` server and is ahead by three and behind by one, meaning that there is one commit on the server we haven't merged in yet and three commits locally that we haven't pushed.
Finally we can see that our `testing` branch is not tracking any remote branch.

It's important to note that these numbers are only since the last time you fetched from each server.
This command does not reach out to the servers, it's telling you about what it has cached from these servers locally.
If you want totally up to date ahead and behind numbers, you'll need to fetch from all your remotes right before running this.
You could do that like this:

[source,console]
----
$ git fetch --all; git branch -vv
----

==== Pulling

(((pulling)))
While the `git fetch` command will fetch all the changes on the server that you don't have yet, it will not modify your working directory at all.
It will simply get the data for you and let you merge it yourself.
However, there is a command called `git pull` which is essentially a `git fetch` immediately followed by a `git merge` in most cases.
If you have a tracking branch set up as demonstrated in the last section, either by explicitly setting it or by having it created for you by the `clone` or `checkout` commands, `git pull` will look up what server and branch your current branch is tracking, fetch from that server and then try to merge in that remote branch.

Generally it's better to simply use the `fetch` and `merge` commands explicitly as the magic of `git pull` can often be confusing.

[[_delete_branches]]
==== Deleting Remote Branches

(((branches, deleting remote)))
Suppose you're done with a remote branch -- say you and your collaborators are finished with a feature and have merged it into your remote's `master` branch (or whatever branch your stable codeline is in).
You can delete a remote branch using the `--delete` option to `git push`.
If you want to delete your `serverfix` branch from the server, you run the following:

[source,console]
----
$ git push origin --delete serverfix
To https://github.com/schacon/simplegit
 - [deleted]         serverfix
----

Basically all this does is to remove the pointer from the server.
The Git server will generally keep the data there for a while until a garbage collection runs, so if it was accidentally deleted, it's often easy to recover.
