Bug#564317: Apt-cache showpkg shows repeated lines

[jidanni@jidanni.org]

Package: apt
Version: 0.7.25
Severity: wishlist
File: /usr/bin/apt-cache

Apt-cache showpkg shows repeated lines
$ apt-cache showpkg iceweasel|sort|uniq -c|sort -n|tail -n 4
      2   xul-ext-notify,iceweasel
      2   xul-ext-pwdhash,iceweasel
      2   xul-ext-webdeveloper,iceweasel
      4   mozilla-openoffice.org,iceweasel

They are even adjacent too,
$ apt-cache showpkg iceweasel|uniq -c|sort -n|tail -n 4
      2   xul-ext-firecookie,iceweasel
      2   xul-ext-firegpg,iceweasel
      2   xul-ext-flashblock,iceweasel
      2   xul-ext-flashgot,iceweasel...

$ apt-config dump|grep Cache
APT::Cache "";
APT::Cache::AllVersions "false";

sources.list has
deb http://ftp.tw.debian.org/debian experimental main contrib non-free
deb http://ftp.tw.debian.org/debian unstable main contrib non-free
deb http://ftp.tw.debian.org/debian-multimedia unstable main