Cloning this repository:

git clone git://gitorious.org/usbflattiny/usbflattiny.git usbflattiny
cd usbflattiny

Add this repository as a remote to an existing local repository:

git remote add usbflattiny git://gitorious.org/usbflattiny/usbflattiny.git
git fetch usbflattiny
git checkout -b my-local-tracking-branch usbflattiny/master_or_other_branch