Redmine

Is there any examples of a plugin that creates a new type of repository in addition to git, svn, etc? It looks like a lot of the functions are pretty tied to core functionality, especially on the repository configuration per project. I'm thinking of attempting to make a github repository type that only takes the github url and handles all the local repo/file stuff behind the scenes, but didn't know if I have to hack it into the core, if I could do it totally as a plugin or not.

If not, then I guess I'll just dig in and see what I can figure out, but figured I would ask first.