Bug#648350: lintian: please check for XZ compression w/o pre-depends: dpkg (>= 1.15.6)

["Aaron M. Ucko" <ucko@debian.org>]

Package: lintian
Version: 2.5.3
Severity: normal

It is possible these days to compress .deb data components with xz;
however, installing the resulting packages requires dpkg (>= 1.15.6).
Within Debian, that's no big deal, as stable (squeeze) has 1.15.8.x;
however, propagation to Ubuntu fails without a corresponding
Pre-Depends: setting, as their current long-term-support stable
release (lucid) merely has 1.15.5.6ubuntuX.  AIUI, Ubuntu should be
able to relax that policy next April or so; until then, though, it
would be great if Lintian could catch such cases itself and give
immediate feedback.  (As it is, the issue may not surface until an
affected package hits testing, from which Ubuntu draws; the resulting
churn is particularly painful given that the prime candidates for XZ
compression tend to be large.)

Could you please add a check along those lines (perhaps cribbed from
Ubuntu)?

Thanks!

-- System Information:
Debian Release: wheezy/sid
  APT prefers testing
  APT policy: (500, 'testing'), (500, 'stable'), (300, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.0.0-2-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages lintian depends on:
ii  binutils                       2.21.90.20111004-2
ii  bzip2                          1.0.5-7           
ii  diffstat                       1.54-1            
ii  file                           5.09-2            
ii  gettext                        0.18.1.1-5        
ii  intltool-debian                0.35.0+20060710.1 
ii  libapt-pkg-perl                0.1.25            
ii  libclass-accessor-perl         0.34-1            
ii  libdigest-sha-perl             5.62-2            
ii  libdpkg-perl                   1.16.1.1          
ii  libemail-valid-perl            0.185-1           
ii  libipc-run-perl                0.90-1            
ii  libparse-debianchangelog-perl  1.2.0-1           
ii  libtimedate-perl               1.2000-1          
ii  liburi-perl                    1.59-1            
ii  locales                        2.13-21           
ii  man-db                         2.6.0.2-2         
ii  patchutils                     0.3.2-1           
ii  perl [libdigest-sha-perl]      5.12.4-6          
ii  unzip                          6.0-5             

lintian recommends no packages.

Versions of packages lintian suggests:
ii  binutils-multiarch     2.21.90.20111004-2   
ii  dpkg-dev               1.16.1.1             
ii  libhtml-parser-perl    3.69-1               
ii  libtext-template-perl  1.45-2               
ii  man-db                 2.6.0.2-2            
ii  xz-utils               5.1.1alpha+20110809-3

-- no debconf information