Code review comment for lp:~michael.nelson/launchpad/distro-series-difference-schema

Michael, 'latest_package_diff' implies 'the newest' but as you say
uploads could be made that mean its not the latest diff after all.

I haven't looked closely yet, but it seems to me that when you
generate a diff you know the versions you generated it against, and
you should store those, then it *is* a package_diff, not a 'latest_'
one, and we can query easily to see if it is or isn't the latest one.