sub-module support

[Bela Babik]

> Analogous to the security saying, "What's your threat model?", I'm
> (trying to be) asking "What, specifically, is the problem that these
> solve for you that is not solved using e.g., multiple, separate
> repositories?"

I think a lot of people would like to use the VCS to manage
projects/dependencies.

If I would need that functionality I would write a script to do it for
me, because it is so simple, but there is always a catch in simple
thinks. No two user need the exact same simple solution.

teki