cd ~/Library/Application\ Support/TextMate/Bundles
git clone git://gitorious.org/git-tmbundle/mainline.git Git.tmbundle
In the TextMate preferences, advanced tab, shell variables, set the TM_GIT variable to point to /opt/local/bin/git (if installed via MacPorts).
Reload bundles (Bundles->Bundle Editor->Reload Bundles).
Now it works as the SVN bundle, but pressing Ctrl+Shift+G.
