Asynchronous VCS command runner
Run bunch of VCS commands (git/hg/bzr) over a set of repositories.
- You want to make sure you pushed changes to remote for all of your repositories.
- You want to log the revision of all of your repositories.
- You are using git but want to have hg/bzr repositories as submodule.
- You want to do (equivalent of) git fetch for all of your repositories.