installing subport from a portdir

[René J . V . Bertin]

Hi,

It's possible to install a port by executing `port install` from within a 
portdir (that is not in a declared ports tree). But as soon as you include a 
port name the local Portfile will be ignored, so how does one install a subport 
from such a portdir, e.g. from a py-foo port where the main port is a stub?

Thanks,
R.