msgmap: note how we use ->created_at

It'll likely be used in the future for JMAP, detached indices,
and maybe other things.

diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index d696ce837395bcbc0800a09e41290f8f1e5fee02..f15875e37cd8a88c2b74956301892d4198be541f 100644 (file)
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -91,6 +91,7 @@ sub last_commit_xap {
        $self->meta_accessor("last_xap$version-$i", $commit);
 }
 
+# this is the UIDVALIDITY for IMAP (cf. RFC 3501 sec 2.3.1.1. item 3)
 sub created_at {
        my ($self, $second) = @_;
        $self->meta_accessor('created_at', $second);