[Cooker] Proper rsync syntax for Cooker downloads

[Robert Fox]

I have been using "wget -rm" to fetch the Cooker tree - but if I do it often enough, I 
end up with a bunch of older files on the downloaded branch 
(because the older version is not removed)

Is rsync or mirror better?  If so, what is the recommended download syntax for using 
rsync or mirror?

Thanks.
RF