Cloning this repository:

git clone git://gitorious.org/meegotouch-marble/meegotouch-marble.git meegotouch-marble
cd meegotouch-marble

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

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