search: remove {mset} option for ->mset method

The ->mset method always returns a Xapian mset nowadays, so
naming a parameter {mset} is too confusing.  As it does with
MiscSearch, setting the {relevance} parameter to -1 now sorts by
ascending docid order.  -2 is now supported for descending
docid order, too, since it may be useful for lei users.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index a3a10bde..2af5ab0c 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -1136,7 +1136,7 @@ sub search_common {
                 my $srch = $self->{ibx}->isrch or
                         return "$tag BAD search not available for mailbox\r\n";
                 my $opt = {
-                        mset => 2,
+                        relevance => -1,
                         limit => UID_SLICE,
                         uid_range => $range_info
                 };