Merge lp://staging/~cjwatson/launchpad/init-packageset-fixes into lp://staging/launchpad

Fix InitializeDistroSeries._copy_packagesets to copy from only the most recent series, not merge packagesets from all series.

== Summary ==

Bug 887185 reports that initialize-distroseries.py has been creating duplicate ArchivePermission rows. Relatedly, I've also noticed that, rather than copying the list of source packages in a given packageset from oneiric to precise when initialising precise (say), it's been merging the source packages in all instances of that packageset name in all distroseries. These look intuitively related, and indeed they turn out to be due to the same underlying bug.

== Proposed fix ==

        packagesets = self._store.find(
            Packageset, DistroSeries.id.is_in(self.derivation_parent_ids))

The intention is obvious here, but that code is missing anything relating the Packageset and Distroseries rows, so it ends up just loading all packagesets. Adding the obvious And(Packageset.distroseries == DistroSeries.id, ...) makes it work.

== Implementation details ==

+49 LoC, but I'd like to get this landed in time for opening Ubuntu Q and so don't want to spend lots of time refactoring if possible; could I use some credit from r15080 (-232) or r15103 (-93)?

== Tests ==

bin/test -vvct test_initialize_distroseries

== Demo and Q/A ==

I'm open to suggestions of something that can be done in practice in a reasonable time. My guess would be that we run initialize-distroseries.py on some suitable series on dogfood and then inspect the results, but I don't know what would be a suitable series and I don't know whether running i-d on dogfood is practical.

== lint ==

None.