Package branch freshness

[Martin Pool]

Thanks for testing this so quickly, Barry.

Some of the verbosity was my idea, just to make sure that people
understood this was specifically a check of the packaging branch
against the published package, and so they wouldn't confuse this with
a message about the wt being out of date.  I agree putting the numbers
at the start would be easier to scan, and your other form would also
work pretty well.

I wonder if we should give a url or some kind of advice on what to do
in the case it is out of date.

Martin