Bug#363389: apt: Explicit zero epoch in package version causes endless upgrading

[Max Bowsher <maxb1@ukf.net>]

Package: apt
Version: 0.6.43.3
Severity: normal

Usually, an epoch value is either absent, and so zero implicitly, or
explicitly present and greater than zero.
If a package version number includes an explicit epoch value of zero,
apt-get misbehaves, considering the version present in the available
download sources to be newer than the installed version, *despite* them
being the exact same version!

This causes the affected package to be reinstalled every time an
'apt-get upgrade' or 'apt-get dist-upgrade' is performed.

Whilst there isn't any particularly reason for a package to include a
zero epoch value explicitly, apt should handle such a situation
gracefully.

This bug was discovered because mailman 0:2.1.7-2.1.8rc1-1 included an
explicit zero epoch.

Max.