I think it happened during 11.2-RELEASE → 12.0-RELEASE, but now after removing a package it gives:
% sudo pkg_rmleaves
diff: unrecognized option `--unchanged-line-format='
Ha, so there are still some people using this port :)
This seems to be due to the switch from GNU diff to BSD diff in FBSD 12. I changed the code to use the comm utility instead. See bug #234769 with the port update.
Fixed by r489827
A commit references this bug:
Date: Wed Jan 9 20:41:05 UTC 2019
New revision: 489827
ports-mgmt/pkg_rmleaves: update 20140222 -> 20190108 to support FBSD 12
- switch from GNU diff to BSD diff needs to be handled
PR: 234769, 234763
Reported by: Lapo Luchini <firstname.lastname@example.org>
Submitted by: email@example.com (maintainer)