archive_old_logs: compress (xz) archived logs

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-s: include arch in the default tarball name

allows running both amd64 and i386 on the same slave with minimal configuration

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

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-m: increase logfile verboseness

Signed-off-by: Andreas Beckmann <anbe@debian.org>
distros.conf: add jessie-proposed-updates

Signed-off-by: Andreas Beckmann <anbe@debian.org>
todo and changelog updates

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/conf.py: add _is_virtual() method

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/conf: exclude virtual distros from expanded list by default

Signed-off-by: Andreas Beckmann <anbe@debian.org>
Slave logs to seconds resolution.

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