imap: support LSUB command

Since we only support read-only operation, we can't save
subscriptions requested by clients.  So just list no inboxes as
subscribed, some MUAs may blindly try to fetch everything its
subscribed to.

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 2282e3ce..51ab8b8c 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -497,6 +497,11 @@ sub cmd_list ($$$$) {
         \(join('', @$l, "$tag OK List done\r\n"));
 }
 
+sub cmd_lsub ($$$$) {
+        my (undef, $tag) = @_; # same args as cmd_list
+        "$tag OK Lsub done\r\n";
+}
+
 sub eml_index_offs_i { # PublicInbox::Eml::each_part callback
         my ($p, $all) = @_;
         my ($eml, undef, $idx) = @$p;