Bug#599523: [update-manager-gnome] wants to downgrade packages without any notice

[Zoran Dzelajlija]

Package: update-manager-gnome
Version: 0.200.4-1
Severity: serious

--- Please enter the report below this line. ---
update-manager wants to downgrade a package I explicitely installed from
experimental without any special notice.  This downgrade would break 
functionality on my machine.  apt and aptitude don't try to do anything
similar, nor suggest it be done.

$ apt-cache policy libgl1-mesa-dri
libgl1-mesa-dri:
  Installed: 7.8.2-2
  Candidate: 7.7.1-4
  Package pin: 7.7.1-4
  Version table:
 *** 7.8.2-2 990
        200 http://debian.iskon.hr/debian/ experimental/main i386 Packages
        100 /var/lib/dpkg/status
     7.7.1-4 990
        700 http://debian.iskon.hr/debian/ testing/main i386 Packages
        300 http://debian.iskon.hr/debian/ unstable/main i386 Packages
     7.0.3-7 990
        400 http://debian.iskon.hr/debian/ stable/main i386 Packages

$ egrep -vh '^[[:blank:]]*//' /etc/apt/apt.conf /etc/apt/apt.conf.d/*
APT::Cache-Limit "33554432";

Acquire
{
  http 
  {
    Timeout "30";
    Pipeline-Depth "5";
    
    No-Cache "false";
    Max-Age "86400";     // 1 Day age on index files
    No-Store "true";    // Prevent the cache from storing archives    
  };
  ftp
  {
   Proxy::ftp.irb.hr "DIRECT";
    Timeout "30";
  };
};
APT
{
  NeverAutoRemove
  {
	"^firmware-linux.*";
	"^linux-firmware$";
	"^linux-image.*";
	"^kfreebsd-image.*";
	"^linux-restricted-modules.*";
	"^linux-ubuntu-modules-.*";
  };

  Never-MarkAuto-Sections
  {
	"metapackages";
	"restricted/metapackages";
	"universe/metapackages";
	"multiverse/metapackages";
	"oldlibs";
	"restricted/oldlibs";
	"universe/oldlibs";
	"multiverse/oldlibs";
  };
};
DPkg::Pre-Install-Pkgs {"/usr/sbin/apt-listbugs apt || exit 10";};
DPkg::Tools::Options::/usr/sbin/apt-listbugs "";
DPkg::Tools::Options::/usr/sbin/apt-listbugs::Version "2";
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "0";
APT::Update::Post-Invoke {"touch /var/lib/apt/periodic/update-success-stamp 2>/dev/null || true";};
APT::Archives::MaxAge "30";
APT::Archives::MinAge "2";
APT::Archives::MaxSize "500";
DPkg::Pre-Install-Pkgs { "/usr/bin/apt-listchanges --apt || test $? -ne 10"; };
DPkg::Tools::Options::/usr/bin/apt-listchanges::Version "2";
DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt || true";};
DPkg::Post-Invoke {"if [ -d /var/lib/update-notifier ]; then touch /var/lib/update-notifier/dpkg-run-stamp; fi; if [ -e /var/lib/update-notifier/updates-available ]; then echo > /var/lib/update-notifier/updates-available; fi "; };

--- System information. ---
Architecture: i386
Kernel:       Linux 2.6.35-trunk-686

Debian Release: squeeze/sid
  700 testing         security.debian.org 
  700 testing         debian.iskon.hr 
  500 squeeze         www.lamaresh.net 
  400 stable          debian.iskon.hr 
  400 stable          deb.opera.com 
  300 unstable        www.debian-multimedia.org 
  300 unstable        debian.iskon.hr 
  200 experimental    debian.iskon.hr 

--- Package information. ---
Depends                     (Version) | Installed
=====================================-+-==============
python                                | 2.6.5-13
python-support            (>= 0.90.0) | 1.0.10
gconf2                  (>= 2.28.1-2) | 2.28.1-4
update-manager-core     (= 0.200.4-1) | 0.200.4-1
python-gconf                          | 2.28.1-1
python-dbus                           | 0.83.1-1
python-gtk2                           | 2.17.0-4
gksu                                  | 2.0.2-3
python-gobject            (>= 2.16.1) | 2.21.4+is.2.21.3-1
python-vte                            | 1:0.24.3-1


Package's Recommends field is empty.

Suggests                     (Version) | Installed
======================================-+-===========
update-notifier                        | 0.99.3debian6
software-properties-gtk                |