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 do not have write access to the revision control archives for those projects. WWW: http://www.gnu.org/software/gnu-arch/