> You commit to the trunk, then you do "svnmerge merge -r<rev>" in the 
> 3k branch, then "svn commit -F svnmerge-something.txt" (in case of
> conflicts, you fix them first, of course).

Done in r72306 for trunk and r72309 for 3k. Thanks.

> I'm not sure - I think the install script must run several times
> actually, so there must be several custom actions, each with its own
> condition.

Yep. That's what the patch does - adds a CustomAction and an entry in
InstallExecuteSequence for each version.

> Well, if there had been separate packages per version, you could 
> install them independently, anyway.

For what it's worth, you still have this option if anyone wants to
distribute multiple MSIs. Simply pass --target-version to bdist_msi, and
you'll get an MSI for only the selected version of Python that you can
install independently of other MSIs generated with --target-version.