Like most people in this thread, I too long for an end to the weird double-commit process that we're using now. So I'm happy to set aside my original Best Practices proposal until there's some consensus regarding how much longer we're going to use that process. Presumably opinions about how to handle merge-from-common commits will vary in the meantime, but that's something we can live with.

In terms of promoting common into a real project, though, I want to raise another option that's guaranteed to be unpopular: We make openstack-common a git-submodule that is automatically checked out within the directory tree of each other project.