I always liked that my Git installations on Unix and Linux comes with the contrib/complete/git-completion.bash script activated or easily activated. But its harder if you use the pre-built binaries for Mac OS X.
To get autocompletion to work on Mac OS X when installing the pre-built binaries do this.
UPDATE: 2013-08-07New URLs to Github. Thanks to fabb.
1. Download the completion script from Github
curl https://raw.github.com/git/git/master/contrib/completion/git-completion.bash -OL
2. Add the following to your ~/.profile or ~/.bash_profile
source ~/git-completion.bash alias gco='git co' alias gci='git ci' alias grb='git rb'
3. Add the following to your ~/.gitconfig
[alias] co = checkout ci = commit rb = rebase
Restart Terminal and start Tabbin’!
More Git tips that I found usefull can be found on Tim Dysinger’s blog http://dysinger.net/2007/12/30/installing-git-on-mac-os-x-105-leopard