Finding depends-on ports

[Beeblebrox]

I'm running a default-settings ports build from a ports-list file in
poudriere (-f /path/file), which means no options have been defined by
"# make config" or by make.conf (empty /var/db/ports, so can't look
there).

Is there an easy way to find or back-trace which forward ports depend on
a certain port without running configure for the whole list? The only
thing I could think of is to write a shell script like: 
cat file-name | while read line
make -C $line all-depends-list | grep <portname>
printf $stuff > outfile

Regards
-- 
FreeBSD_amd64_12-Current_RadeonKMS
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