Hi Marc, I'm afraid having a different upstream/pristine-tar messed up things.
even if the tarball is the same, git fails to see a common history. I did create a new repository http://anonscm.debian.org/cgit/collab-maint/borgbackup-new.git (for some reasons your repo has the wrong permission bit set) But I honestly prefer Danny's repository, https://github.com/dannyedel/pkg-borgbackup because he fixed a lot of stuff, including regeneration of built file at build time. what do you think? cheers, G.