SSH access with hg and git user names
See heptapod-docker#3 (closed) for a previous incarnation.
It would be nice if we could introduce a hg
user name for SSH, even if it's purely virtual, so that both ssh://hg@heptapod.example
and ssh://git@heptapod.example
would work. Bonus would be to reserve the first to Mercurial projects and the second to Git projects.