What has happened here is that in the last change, we changed the Packager from ourDelta to Monty Program (which is in fact, accurate).
We can fix this similarly to http://bugs.mysql.com/bug.php?id=45534
The fix is actually here: http://bazaar.launchpad.net/~mysql/mysql-server/5.1/view/head:/support-files/mysql.spec.sh
The workaround is to:
%define mysql_old_vendor OurDelta - http://ourdelta.org/
%define mysql_vendor Monty Program - http://www.montyprogram.com/
The 649-689 lines in mysql.spec.sh is the logic behind making a "safe" upgrade
Do you want me to fix this and patch it in bakery, or will you do it?