+ # The above guess-code takes into account the problem below.
+
+ # XXX I just thought of a problem, but we might be able to get away with it
+ # anyway! The problem is when mhpath has more message paths to output than
+ # fit in the pipe buffer, it blocks WHILE HOLDING THE SEQUENCE LOCK.
+ # If there's a message in there that stays in inbox, minc renames it, and
+ # tries to lock the sequence file, and we DEADLOCK. However, if we do
+ # nothing with sequences at all for the inbox folder, I think everything
+ # just works! inc has added everything to unseen already. If we don't
+ # touch it, we have an unseen list that includes a bunch of messages that
+ # are gone, and the ones that stayed in inbox are already) included in that
+ # list! The next inc (or any other sequence-writing operation) should elide
+ # the now-non-existent messages from unseen. It just might work!
+