Improve the gbp.conf template
-
The Debian packaging branch and the upstream import branch names should follow DEP-14 conventions. The debian-branch should never be 'main' as it is likely to clash with the upstream development branch name.
-
A good gbp.conf has at minimum documented if and what upstream release git tag format is, and if Debian packaging uses tarballs or not (and hence if pristine-tar should be expected). These are things that git-buildpackage can't guess and thus makes sense to recommend as the bare minimum contents for gbp.conf.