Cloning this repository:

git clone git://gitorious.org/+tiled-developers/tiled/tiled-developers-tiled-qt.git tiled-developers-tiled-qt
cd tiled-developers-tiled-qt

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

git remote add tiled-developers-tiled-qt git://gitorious.org/+tiled-developers/tiled/tiled-developers-tiled-qt.git
git fetch tiled-developers-tiled-qt
git checkout -b my-local-tracking-branch tiled-developers-tiled-qt/master_or_other_branch