Bug#792096: borg packaging: Update

["Danny B. Edel" <debian@danny-edel.de>]

Hello everyone,

borgbackup-0.27.0-1 has been packaged and uploaded, and is in the [new]
queue.  The package is being maintained in collab-maint, all extra
repositories and branches on collab-maint or github have been deleted.

Since python3-setuptools-scm will behave differently when called in a
git clone (it will attempt to construct a version number from the
current git commit, which will point to the debian packaging and not the
upstream code), a gbp.conf file has been added that makes use of the
[export-dir] mechanism.  That way, python3-setuptools-scm falls back to
reading the metadata files included in the directory (since it will be
called outside the git clone), creating the correct (upstream) version
number.

- Danny

[new]: https://ftp-master.debian.org/new.html
[export-dir]:
http://honk.sigxcpu.org/projects/git-buildpackage/manual-html/gbp.building.html#GBP.BUILDING.EXPORT