Goals for Fedora Workstation upgrades

[Owen Taylor]

The discussion about F20 to F21 upgrades has been largely focused on the
technolaogy - what will happen if we make package X depend on package Y
and obsolete package Z. I understand the motivation behind wanting
upgrades to be encoded in the package set and to keep special casing to
a minimum. But I think we can't just shrug and consider that the end -
we need to know what we are trying to achieve to figure out when we need
to special case and do ugly things to get there.

Before going too far into the practicalities of what we can achieve for
Fedora 21, I decided try to write down what we'd want for F21 => F22 and
beyond. I mean this to be Workstation specific - not apply to other
products or non-productized installations of Fedora.

 * The end result of an upgrade to F<n> must have all the packages that
would have been installed  for a fresh install of F<n>

 * In general, packages that were originally installed by default on the
system, but no longer installed by default in F<n> should be removed.
This may not always be practical, but after the upgrade:
   - There must be no duplication of applications in system roles. For
example, there must not be two character map applications
   - There should be no left over system services started at boot
 If a default application is removed without any replacement in the new
default set (e.g. we stop installing an office suite), leaving the old
application is acceptable.

 * Normal user configuration of the pre-upgraded system via
(non-tweak-tool) desktop configuration must not leave the system in a
broken state after the upgrade.

 * After the upgrade, the user should see the new defaults for things
like backgrounds unless they have explicitly configured non-default
settings.

 * We test the following upgrades:

   fresh install F<n-1> => f<n>
   fresh install F<n-2> => f<n>
   serial upgrade fresh install F<n0> => F<n0+1> => ... f<n> (n0 to be
determined - f20 or f21 most likely)