{cvs, tar}.py: Fixes assignment for self.branch

Fixes commit: fix undefined 'subpath', update tests
SHA:0fde69e7ef993c3e5cca925cef35c8c895cfd834
Author: dol-sen <brian.dolbec@gmail.com>
Date: Sat 23 Jul 2011 02:44:26 AM EDT
darcs.py: Adds module branch support
git.py: Adds module branch support
mercurial.py: Adds module branch support