Arch is a really nifty revision control system. It's "whole-tree
changeset based" which means, roughly, that it can handle (with atomic
commits) file and directory adds, deletes, and renames cleanly, and
that it does branching simply and easily. Arch is also "distributed"
which means, for example that you can make arch branches of your own
from remote projects, even if you don't have write access to the
revision control archives for those projects. 

WWW: http://gnuarch.org/