lei import: import IMAP flag changes from old messages

This makes "lei import" behavior with IMAP folders more
consistent with that with Maildir.

Opening IMAP folders read-write with "SELECT" (instead of
read-only with "EXAMINE") was necessary, since it lets an IMAP
server communicate to us as to whether or not it's worth
refetching IMAP flags of previously imported messages.

Fetching UID+FLAGS only is one of the fastest IMAP operations
with dovecot, our -imapd and presumably other common IMAP servers.
It is issued by common MUAs such as mutt after every SELECT.

Users may now rely on "lei import" exclusively to merge mail and
keywords into lei/store, and "lei export-kw" to propagate
keyword changes back to IMAP servers.

A sticks-and-stones workflow for personal mailboxes is currently:

	lei import imaps://$MY_PERSONAL_INBOX
	lei q --mua=$MUA -o /tmp/results SEARCH TERMS...
	# do stuff from within $MUA to /tmp/results
	lei import /tmp/results # read keyword changes from MUA
	lei export-kw imaps://$MY_PERSONAL_INBOX
	# repeat when new stuff shows up in personal inbox

The next goal is to automate repeated imports + export-kw
commands with with inotify and IMAP IDLE.

1 files changed, 16 insertions, 2 deletions

diff --git a/lib/PublicInbox/LeiImport.pm b/lib/PublicInbox/LeiImport.pm
index 01e6c93c..f9a46ec5 100644
--- a/lib/PublicInbox/LeiImport.pm
+++ b/lib/PublicInbox/LeiImport.pm
@@ -45,7 +45,16 @@ sub input_net_cb { # imap_each / nntp_each
         my ($uri, $uid, $kw, $eml, $self) = @_;
         my $vmd = $self->{-import_kw} ? { kw => $kw } : undef;
         $vmd->{sync_info} = [ $$uri, $uid ] if $self->{-mail_sync};
-        $self->input_eml_cb($eml, $vmd);
+        if (defined $eml) {
+                $self->input_eml_cb($eml, $vmd);
+        } elsif ($vmd) { # old message, kw only
+                my $oid = $self->{-lms_ro}->imap_oid2($uri, $uid) // return;
+                my @docids = $self->{lse}->over->blob_exists($oid) or return;
+                my $lei = $self->{lei};
+                $lei->qerr("# $oid => @$kw\n") if $lei->{opt}->{verbose};
+                $self->{lei}->{sto}->ipc_do('set_eml_vmd', undef,
+                                                $vmd, \@docids);
+        }
 }
 
 sub do_import_index ($$@) {
@@ -65,7 +74,12 @@ sub do_import_index ($$@) {
                 # $j = $net->net_concurrency($j); TODO
                 if ($lei->{opt}->{incremental} // 1) {
                         $net->{incremental} = 1;
-                        $net->{-lms_ro} = $lei->_lei_store->search->lms // 0;
+                        $net->{-lms_ro} = $sto->search->lms // 0;
+                        if ($self->{-import_kw}) {
+                                $net->{each_old} = 1;
+                                $self->{-lms_ro} = $net->{-lms_ro};
+                                $self->{lse} = $sto->search;
+                        }
                 }
         } else {
                 my $nproc = $self->detect_nproc;