How to get a full list of dependents?

[Ian Wadham]

Apparently commands such as "port dependents xxx" or "port echo dependentof:xxx"
will only list *installed* dependents --- and "xxx" must itself be installed.

How can I get a full list of ports that are dependents of "xxx", whether or not
they or "xxx" are installed?

ATM I would like to see which ports depend on Growl and which depend on
MacPorts_Framework.  Pallet depends on both, but are there others?

If I wish to make a change in MacPorts_Framework, what might be the impact
on ports other than Pallet, or is Pallet the only user?

Ditto, if I wish to remove the dependency of Pallet on Growl?  Do other ports
use it successfully?  It is apparently not doing anything in Pallet.

All the best, Ian W.