Support other code-sharing sites besides GitHub

[ajpiano]

GitHub is awesome, but some people prefer other sites, like BitBucket, for their repository hosting. It would be ideal if we can only require "open source development," not "open source development on GitHub only."

[rdworth]

It does simplify development a great deal to support only GitHub from the start. That said, nothing in the design of the system today prevents us from being able add support for other git hosting services in the future. Most of what we do is git-generic, not GitHub-specific. Some things that today are GitHub-specific could be made service-generic, whether we want to add a few or n different services. Though this is possible, in order to limit scope initially, we're not building in this way, at least not yet. We'll continue to keep aware of this requirement and ensure this change will always be possible, even if it happens after the initial launch of the site.

[scottgonzalez]

I've started abstracting out anything specific to getting and parsing code. I don't really understand Bitbucket's services and brokers, but I'm sure we can handle it pretty similarly to GitHub. We may have to change some sync GitHub code to be async if Bitbucket doesn't provide the same data (like watchers and forks) in their hooks, but that's an easy change to make later. I haven't done anything with templates yet (to abstract things like "Fork on GitHub"), but I think that's as far as we should go for now.

[scottgonzalez]

I'm going to consider this done. There should be enough abstraction to handle any other services. We can open issues for specific services when (and if) there is enough demand.