pk4™ provides an easy way to fetch the sources of packages currently installed on the system. In order to let pk4 provide these packages as Git™ repositories you can enable gbp's unpack hook:

mkdir -p ~/.config/pk4/hooks-enabled/unpack/
ln -s /usr/share/pk4/hooks-available/unpack/gbp ~/.config/pk4/hooks-enabled/unpack/
      

This will make sure packages are imported into a git repository after download.