Bug#869921: apt: Pinning the local version of a package no longer works

[Frédéric Brière <fbriere@fbriere.net>]

Package: apt
Version: 1.1
Severity: normal

Pinning the local version of a package, as documented in
apt_preferences(5), seems to have been broken between jessie and
stretch:

  Contents of /etc/apt/preferences:

    Package: hello
    Pin: origin ""
    Pin-Priority: 999

  Output of "apt-cache policy hello" on jessie:

    hello:
      Installed: 2.8-1
      Candidate: 2.8-1
      Package pin: (not found)
      Version table:
         2.9-2+deb8u1 999
            500 http://httpredir.debian.org/debian/ jessie/main amd64 Packages
     *** 2.8-1 999
            100 /var/lib/dpkg/status

  Output of "apt-cache policy hello" on stretch:

    hello:
      Installed: 2.8-1
      Candidate: 2.10-1+b1
      Version table:
         2.10-1+b1 500
            500 http://httpredir.debian.org/debian stretch/main amd64 Packages
     *** 2.8-1 100
            100 /var/lib/dpkg/status


The behavior of "apt-get upgrade" confirms this: the package is pinned
to the local version on jessie, but is upgraded on stretch (and sid).

After bisecting a bit with snapshots, this was apparently introduced
between 1.0.10.2 and 1.1.


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

Kernel: Linux 4.9.0-3-amd64 (SMP w/3 CPU cores)
Locale: LANG=en_CA.UTF-8, LC_CTYPE=en_CA.UTF-8 (charmap=UTF-8), LANGUAGE=en_CA.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)