Filer is an in-development version control system.
A prototype is available at http://hg.opengroove.org/afn/file/tip/filer. It has init, log, commit, and local push support.
A release will be posted to PyPI once merge and remote push are complete; I expect this to be sometime between September and December of 2012. (It’s August 2012 as of this writing.)
Filer is quite good at delta compression; a sample repository that’s 240KB in Mercurial is around 100KB in Filer.