Makefile: add tg-deps target

for maintainer (i.e. my) convenience only
update the topgit dependency plot

Signed-off-by: Andreas Beckmann <anbe@debian.org>
detect_piuparts_issues: detect another tar error

tar: Error is not recoverable: exiting now

Signed-off-by: Andreas Beckmann <anbe@debian.org>
post_*_squeeze-backports: some special handling needed

similarily to experimental we can't easily use
  apt-get dist-upgrade -t squeeze-backports
so maintain a list of packages in the minimal base system that
need to be upgraded in the reference system to bpo to avoid mismatches

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p.conf: add wheezy2bpo2jessie

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/conf: expand depends in O(n) instead of O(n^2)

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/conf: clarify a variable name

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/conf: resolve virtual distros when querying mirror or distro

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-s: exit gracefully if no sections were found

Signed-off-by: Andreas Beckmann <anbe@debian.org>