Bug#890468: lintian: source-is-missing false positive when d/missing-sources/foo is a symlink

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

Package: lintian
Version: 2.5.75
Severity: normal

consider a package whose upstream ships two binaries, ./foo and ./bar

those two binaries are generated from the same source code, perhaps
compiled in different ways (in my silly example, "make foo" and "make
bar" apply different build flags to the same source tree)

a reasonable configuration for the debian repository is:

  debian/missing-sources/bar/
  debian/missing-sources/bar/Makefile
  debian/missing-sources/bar/main.c
  debian/missing-sources/foo → bar

However, in this case, lintian will complain with:

 package: source-is-missing foo

It doesn't make sense to encourage the package maintainer to ship two
copies of the same source.

   --dkg

-- System Information:
Debian Release: buster/sid
  APT prefers testing-debug
  APT policy: (500, 'testing-debug'), (500, 'testing'), (500, 'oldstable'), (200, 'unstable-debug'), (200, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.14.0-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages lintian depends on:
ii  binutils                          2.30-4
ii  bzip2                             1.0.6-8.1
ii  diffstat                          1.61-1+b1
ii  dpkg                              1.19.0.5
ii  file                              1:5.32-1
ii  gettext                           0.19.8.1-4
ii  intltool-debian                   0.35.0+20060710.4
ii  libapt-pkg-perl                   0.1.33
ii  libarchive-zip-perl               1.60-1
ii  libclass-accessor-perl            0.51-1
ii  libclone-perl                     0.39-1
ii  libdpkg-perl                      1.19.0.5
ii  libemail-valid-perl               1.202-1
ii  libfile-basedir-perl              0.07-1
ii  libipc-run-perl                   0.96-1
ii  liblist-moreutils-perl            0.416-1+b3
ii  libparse-debianchangelog-perl     1.2.0-12
ii  libperl5.24 [libdigest-sha-perl]  5.24.1-7
ii  libperl5.26 [libdigest-sha-perl]  5.26.1-4
ii  libtext-levenshtein-perl          0.13-1
ii  libtimedate-perl                  2.3000-2
ii  liburi-perl                       1.73-1
ii  libxml-simple-perl                2.24-1
ii  libyaml-libyaml-perl              0.69+repack-1
ii  man-db                            2.7.6.1-4
ii  patchutils                        0.3.4-2
ii  perl                              5.26.1-4
ii  t1utils                           1.41-2
ii  xz-utils                          5.2.2-1.3

Versions of packages lintian recommends:
pn  libperlio-gzip-perl  <none>

Versions of packages lintian suggests:
pn  binutils-multiarch     <none>
ii  dpkg-dev               1.19.0.5
ii  libhtml-parser-perl    3.72-3+b2
ii  libtext-template-perl  1.47-1

-- no debconf information