What is "origin" in Git?

When I run:

git push origin branchname

What exactly is origin and why do I have to type it before the branch name?

origin is an alias on your system for a particular remote repository. It's not actually a property of that repository.

By doing

git push origin branchname

you're saying to push to the origin repository. There's no requirement to name the remote repository origin: in fact the same repository could have a different alias for another developer.

Remotes are simply an alias that store the URL of repositories. You can see what URL belongs to each remote by using

git remote -v

In the push command, you can use remotes or you can simply use a URL directly. An example that uses the URL:

git push [email protected]:git/git.git master

origin is not the remote repository name. It is rather a local alias set as a key in place of the remote repository URL.

It avoids the user having to type the whole remote URL when prompting a push.

This name is set by default and for convention by Git when cloning from a remote for the first time.

This alias name is not hard coded and could be changed using following command prompt:

git remote rename origin mynewalias

Take a look at http://git-scm.com/docs/git-remote for further clarifications.

Git has the concept of "remotes", which are simply URLs to other copies of your repository. When you clone another repository, Git automatically creates a remote named "origin" and points to it.

You can see more information about the remote by typing git remote show origin.

origin is the default alias to the URL of your remote repository.

Simple! "origin" is just what you nicknamed your remote repository when you ran a command like this:

git remote add origin [email protected]:USERNAME/REPOSITORY-NAME.git

From then on Git knows that "origin" points to that specific repository (in this case a GitHub repository). You could have named it "github" or "repo" or whatever you wanted.