Bug#765521: Add a warning if a packages targets a backport and only one entry is found on the .changes file

[Lisandro Damián Nicanor Pérez Meyer <lisandro@debian.org>]

Package: lintian
Version: 2.5.28
Severity: wishlist

for(int i=0; i<3; i++) {
  build package for wheezy-backports
  run lintian over it
  sign it
  push it to the archive
  sleep 3'
  realize you forgot to use the -v flag while building
}

Yes, it has happened me three times already. Fault is on my side, but it
would be cool if lintian could somehow detect the package is a backport
(maybe dtecting $DISTRO-backports in the changelog) and notice there is
only one changelog entry in the resulting .changes.

In this case a warning should be issued.

Is this feasible?

-- System Information:
Debian Release: jessie/sid
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.16-2-amd64 (SMP w/2 CPU cores)
Locale: LANG=es_AR.UTF-8, LC_CTYPE=es_AR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages lintian depends on:
ii  binutils                       2.24.51.20141001-1
ii  bzip2                          1.0.6-7
ii  diffstat                       1.58-1
ii  file                           1:5.19-2
ii  gettext                        0.19.2-2
ii  hardening-includes             2.6
ii  intltool-debian                0.35.0+20060710.1
ii  libapt-pkg-perl                0.1.29+b2
ii  libarchive-zip-perl            1.38-1
ii  libclass-accessor-perl         0.34-1
ii  libclone-perl                  0.37-1+b1
ii  libdpkg-perl                   1.17.13
ii  libemail-valid-perl            1.195-1
ii  libfile-basedir-perl           0.03-1
ii  libipc-run-perl                0.92-1
ii  liblist-moreutils-perl         0.33-2+b1
ii  libparse-debianchangelog-perl  1.2.0-1.1
ii  libtext-levenshtein-perl       0.09-1
ii  libtimedate-perl               2.3000-2
ii  liburi-perl                    1.64-1
ii  man-db                         2.7.0.2-1
ii  patchutils                     0.3.3-1
ii  perl [libdigest-sha-perl]      5.20.1-1
ii  t1utils                        1.37-2.1

Versions of packages lintian recommends:
pn  libperlio-gzip-perl             <none>
ii  perl                            5.20.1-1
ii  perl-modules [libautodie-perl]  5.20.1-1

Versions of packages lintian suggests:
pn  binutils-multiarch     <none>
ii  dpkg-dev               1.17.13
ii  libhtml-parser-perl    3.71-1+b2
ii  libtext-template-perl  1.46-1
ii  libyaml-perl           1.12-1
ii  xz-utils               5.1.1alpha+20120614-2

-- no debconf information