Snow Leopard ate my ports

[Alexy Khrabrov]

So I upgraded to SL, just to get port command to spit abuse about
images all being wrong now.  By contrast to 32 bit => 64 bit upgrade,
my old port setup doesn't work anymore so I can't follow the procedure
for re-installing ports by creating a list of those previously
installed with the "list installed" command.

How do I extract the exact list of ports to re-install from my
now-useless old setup?

Cheers,
Alexy