force rebuild a port

[Riccardo Mottola]

Hi!

suppose I want to rebuild a port, but it has no version update.
1) e.g. rev-upgrade shows it to be rebuild but "port outdated" doesn't 
show it.
2) Or I want to rebuild it with a different compiler.

How can I do? "port upgrade X" will do nothing because X is not outdated.
"port upgrade --force X" will upgrade all dependencies, which is a 
little too much...

1) in my case has issues because it wants to rebuild many packages and 
starts with one that breaks, so it never gets to the next one.
I tried using "-p" but apparently it is not respected for "port -p 
rev-upgrade" and still dies.

Riccardo