If you set up a mirror on an empty repository, every minute when it tries to push to the mirror it gets an error.
No refs in common and none specified; doing nothing.
Perhaps you should specify a branch such as 'master'.
fatal: The remote end hung up unexpectedly
This makes sense, since both are empty, there is nothing in common and git should return an error, but it would be nice if didn't cause the error.
I'm not positive how to implement this in a way that it wouldn't silence actual errors though. Perhaps before we mirror, we could check if we actually have any commits, and if we don't, don't try to push to the mirror.