I have made available a completely unofficial but functional MacOS Leopard build of git and the excellent GitNub viewer. To install, pretend I'm a trustworthy individual and run:
curl http://jelder.s3.amazonaws.com/git-1.6.1-leopard.tar.gz | sudo tar xvzf - -C /
This will put git in /usr/local/bin/git (with other support files in /usr/local/libexec and /usr/local/share). The nub script in /usr/local/bin/nub will launch GitNub from the current directory.