Bug#208874: apt: Upgrade tries to install new libc-udeb as well as existing libc6

[Petter Reinholdtsen <pere@hungry.com>]

Package: apt
Version: 0.5.10

There seem to be a bug in apt, making try to install udebs if they are
available from an APT source.  Notice how it tries to install
libc-udeb, even if libc6 is the real package to upgrade.

  [...]
  The following NEW packages will be installed:
    libc-udeb
  The following packages will be upgraded
    cron ifupdown libc6 libc6-dbg libc6-dev libc6-pic locales m4 sudo
  9 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
  Need to get 21.0MB of archives.
  After unpacking 3261kB of additional disk space will be used.
  Do you want to continue? [Y/n] n
  Abort.
  # apt-cache showpkg libc-udeb
  Package: libc-udeb
  Versions:
  2.3.2-5(/var/lib/apt/lists/ftp.skolelinux.no_debian_dists_unstable_main_debian-installer_binary-i386_Packages)

  Reverse Depends:
    autopartkit,libc-udeb
    autopartkit,libc-udeb
    autopartkit,libc-udeb
    slang1a-utf8-udeb,libc-udeb
    nano-udeb,libc-udeb
    bogl-bterm-udeb,libc-udeb
    autopartkit,libc-udeb
    anna,libc-udeb
  Dependencies:
  2.3.2-5 -
  Provides:
  2.3.2-5 - glibc-2.3.2-5
  Reverse Provides:
  #

This is the content of /etc/apt/sources.list.

  deb ftp://ftp.skolelinux.no/debian/ unstable main contrib non-free
  deb ftp://ftp.skolelinux.no/debian-non-US/ unstable/non-US main contrib non-free
  deb http://ftp.skolelinux.no/debian unstable main/debian-installer
  deb ftp://ftp.skolelinux.no/skolelinux sid local/debian-installer

The udeb is available in the main/debian-installer mirror.

After installing only the upgraded packages (apt-get install cron
ifupdown libc6 libc6-dbg libc6-dev libc6-pic locales m4 sudo), I try
to run 'apt-get upgrade' again, and this time it doesn't try to
install libc-udeb:

  # apt-get upgrade
  Reading Package Lists... Done
  Building Dependency Tree... Done
  0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
  #

Could there be a bug in the libc-udeb instead?