It's Magit! A Emacs mode for Git.

the source: git clone git://gitorious.org/magit/mainline.git
git clone http://git.gitorious.org/magit/mainline.git
a tarball: magit-0.7.tar.gz
the docs: User Manual
the cheats: Cheat Sheet (by Daemian Mack)
the jive: Mailing List