"search --duplicate=2 --output=messages" is deranged

[David Edmondson]

Consider:

: disaster-area; notmuch search --output=files id:87hbph5yww.fsf at aw.hh.sledj.net
/home/dme/Maildir/mail/list/notmuch/xx01550
: disaster-area; notmuch search --duplicate=2 --output=files id:87hbph5yww.fsf at aw.hh.sledj.net
: disaster-area; notmuch search --duplicate=2 --output=messages id:87hbph5yww.fsf at aw.hh.sledj.net
id:87hbph5yww.fsf at aw.hh.sledj.net
: disaster-area; 

There's only one file, but the last search which asks for results where
there are more than one reports the message id.