Removing obsolete configuration files on upgrade

[Jonathan Nieder <jrnieder@gmail.com>]

Hi policy experts,

Since policy 3.8.5.0, section 10.7.3 says

	Obsolete configuration files without local changes should be
	removed by the package during upgrade.

I was trying to apply this to the git package and ran into a little
trouble.  Consider the following sequence of events:

 1. I install package hello-demo version 1, including a conffile
    /etc/greeting with content 'hello'.

 2. I change /etc/greeting to 'hi'.

 3. I upgrade hello-demo to version 2, which dropped the customizable
    greeting functionality.  /etc/greeting is obsolete now.  Since
    my greeting was customized, it is retained in /etc/greeting.

 4. I change /etc/greeting back to 'hello'.

 5. I upgrade hello-demo to version 3, which still does not support
    customizable greetings.

Should /etc/greeting be removed during the upgrade?  After all, it
is both (a) obsolete and (b) without local changes from the version 1
of the conffile.

My hunch is to say that a package may remove /etc/greeting in this
case but by no means should.  That is, something like the following
but hopefully less awkward:

	Obsolete configuration files without local changes may be
	removed by the package during upgrade, and should be removed
	by the package during upgrade from the version before they
	were obsolete.

What do you think?

Thanks,
Jonathan