[Lazare]

I've mentioned this elsewhere in this discussion, but: https://github.com/ramasilveyra/gitpkg

I've been using it a bit, and it's really nice. Yarn (and the npm command line tool) already provide nice methods to install packages from arbitrary locations, including git repos; this provides a nice mechanism for publishing to git repos. It's a super simple solution, but then, it's not really a hard problem.