Switching default dpkg-deb compressor to xz

[Guillem Jover <guillem@debian.org>]

Hi!

As mentioned some months ago [0], I'm planning to switch dpkg-deb default
compressor from gzip to xz, as there seemed to be consensus that was
the way to go, and given the amount of already manually switched
packages, or packaging helpers. :/

  [0] <http://lists.debian.org/debian-devel/2012/08/msg00822.html>

The only previous dissenting argument was that the base system (the
one generated by debootstrap), should keep using gz as the compression
format so that it can work on other systems where xz is not easily
available. But Steve McIntyre then mentioned that even that had
changed during DebConf and it was not deemed worth it. I don't mind
either way.

If there's people who are still worried about that, I'd ask them to
file bugs on the base packages to make them pass -Zgz explicitly to
dpkg-deb (I'll do that for dpkg.deb in any case), and I can wait for
the base system to be switched, but those packages could always be
changed on their next upload, or even a fatal lintian error created
so that ftp-master can reject those (I don't think there's one
currently?). Otherwise I'll be doing the change with the dpkg 1.17.0
upload.

Thanks,
Guillem