test-bot expects the dependencies returned from SoftwareSpec#deps to
satisfy is_a?(TapDependency) if they come from a tap which might need to
be tapped.
We're (finally) working on a documented public API for Homebrew. It's currently a work in progress; a bunch of public stuff is documented and a bunch of private stuff is undocumented. Sorry about that!
The main class you should look at is {Formula}. Assume everything else is private for now.