Git is a version control system, like Mercurial with slightly more confusing commands, or like Subversion on steroids. It's a distributed VCS (DVCS), which you can google to find out more about, but if you've only ever used subversion and CVS, you'll find it a little different (hopefully more pleasant) to work with then you're used to.
At some stage, someone might put up a full tutorial showing how to use git, but for now, here's how to get and use a repository on redbrick's git hosting area.
Getting a git repository on Redbrick
Before you can use redbrick's git repositories from one of your computers (or from your redbrick shell), you need to create a public/private SSH keypair there if you haven't already. You'll need to do this for every device/place that you want to access git from. This might sound annoying, but it also lets you use git without having to type a password every time you need to clone/push/pull.
To do this on a Unixey (Linux/Mac OS X/on redbrick) system, run:
ssh-keygen -t rsa
[you@your-computer ~]$ ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/Users/you/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /Users/you/.ssh/id_rsa. Your public key has been saved in /Users/you/.ssh/id_rsa.pub. The key fingerprint is: 58:06:86:0c:83:5e:4e:ab:75:93:96:37:76:42:73:07 email@example.com The key's randomart image is: +--[ RSA 2048]----+ | .oo .o E. | |. +o. + . . | |. + . + = . | | . + * O . | | o o = S | | . | | | | | | | +-----------------+ [you@your-computer ~]$