SRU request for new DPKG::StopOnError config

Binary package hint: apt

The current version of apt will order a install into various chunks of "dpkg --unpack", "dpkg --configure" runs. When dpkg aborts in one of those runs apt will stop the install. This is not desired on a release-upgrade usually because if a early package fails (e.g. dmsetup) this causes the upgrade to leave many packages in a upgradable state. In the worst case it can break so that e.g. a new nvidia-kernel module is installed and but no new xserver package is installed leaving the system without X.

The following patch changes the behaviour so that it will keep runing as long as possible. It will not change the default behaviour in apt-get, but only change the behaviour if it is explicitely set (e.g. in the upgrader).

Please consider it for a SRU. I will post statistics with and without the patch.

On a experiment current edgy->feisty upgrade (with a broken dmsetup, ipvsadm) the stats are:

Without the patch:
- breaks on dmsetup
- 4688 packages installed, 2091 packages still upgradable, 2 broken

With the patch and -o DPkg::StopOnError=false
- breaks on dmsetup, clvm, redhat-cluster-suite, ubuntu-desktop, zope3-sandbox, ipvsadm, multipath-tools
- 4783 packages installed, 7 packages still upgradable, 1 broken

Cheers,
 Michael