Because Debian is all about cooperation and making the git repository
available is an essential step in the process. We currently use
alioth.debian.org for that purpose but it's not related to our standard
packaging process and the logic to go further is either the idea of Joey
(upload git repository as source) or someone in ftpmaster that implements
a direct connection between a git repository and incoming, so that we can
upload packages throught a git repository (and thus have a real canonical
git repository for a given package).