tla -- The Low-Budget Arch Revision Control System
http://www.gnu.org/software/gnu-arch/
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.