Upgrade/Install in one command?

[Atom Powers]

I would like to make my configuration management system update and/or
install packages on FreeBSD. I've been avoiding that little thorn
because I haven't had very many hosts and updates have been fairly
rare recently; but no more. (cfengine2)

Basically, I wish pkg_add would upgrade a package if it was already
installed; of that portupgrade would install a package if it was
missing. Neither seem to work.

How do you manage packages on a large number of FreeBSD hosts?

-- 
Perfection is just a word I use occasionally with mustard.
--Atom Powers--