The debian/ directory is in the debian branch. He uses the 'No upstream tarballs' layout (master points to upstream's master branch) and configures the layout in debian/gbp.conf.
http://honk.sigxcpu.org/projects/git-buildpackage/manual-html/gbp.import.upstream-git.html#gbp.import.upstream.git.notarball
signature.asc
Description: This is a digitally signed message part