[Merge] ~rbalint/ubuntu-release-upgrader:ubuntu/master into ubuntu-release-upgrader:ubuntu/master

[Dimitri John Ledkov]

Review: Needs Fixing can-of-warms

Digging into this, I am opening up a can of warms it seems.

First we try to determine if we should go into "desktop" or "server" mode. This is done by trying to detect "keydependencies" of metapackages.

For example, key dependency for kubuntu-desktop is plasma-desktop. However for ubuntu-desktop it is "lightdm, unity, ubuntu-artwork, ubuntu-sounds" which imho is an out of date list. It should be "gnome-shell, gdm3".

Also I do not see any ubuntu-desktop-minimal handling, of how to upgrade a minimal ubuntu desktop.

Next in server mode, we try to gather a list of all tasks installed... However we do not exclude tasks, that are configured as BaseMetaPkgs "ubuntu-minimal, ubuntu-standard". Those are already installed under keepBaseMetaPkgsInstalled rule anyway.

I also noticed that we have stray tasks. Specifically "ubuntu-core" is still a task, despite the metapackage getting removed. We should ignore this task.

If we fix above, a situation that timesyncd has fallen uder will not materialize, and this special casing then would not be needed.
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https://code.launchpad.net/~rbalint/ubuntu-release-upgrader/+git/ubuntu-release-upgrader/+merge/382454
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