lei import: support --new-only for IMAP

Taking ~40s to synchronize a ~75K message IMAP folder is
still a lot of time, so support an option to only touch
new messages.

This is similar to "offlineimap -q" (quick) or "mbsync --new"
switches, but lei already accepts "-q" as a shortcut for
--quiet.  "--new" could work, but "--new-only" might be more
descriptive (or "--only-new"?), since the default fetches
also fetches new messages.

v2: warn for non-IMAP sources, I'm not sure it's worth it for
    Maildir or other sources, yet.  It will also make sense
    for MH and JMAP once we support them.

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/PublicInbox/LeiImport.pm b/lib/PublicInbox/LeiImport.pm
index e3cb69ca..08794f71 100644
--- a/lib/PublicInbox/LeiImport.pm
+++ b/lib/PublicInbox/LeiImport.pm
@@ -78,12 +78,14 @@ sub do_import_index ($$@) {
         $j =~ /\A([0-9]+),[0-9]+\z/ and $j = $1 + 0;
         $j ||= scalar(@{$self->{inputs}}) || 1;
         my $ikw;
-        if (my $net = $lei->{net}) {
+        my $net = $lei->{net};
+        if ($net) {
                 # $j = $net->net_concurrency($j); TODO
                 if ($lei->{opt}->{incremental} // 1) {
                         $net->{incremental} = 1;
                         $net->{-lms_ro} = $sto->search->lms // 0;
                         if ($self->{-import_kw} && $net->{-lms_ro} &&
+                                        !$lei->{opt}->{'new-only'} &&
                                         $net->{imap_order}) {
                                 require PublicInbox::LeiImportKw;
                                 $ikw = PublicInbox::LeiImportKw->new($lei);
@@ -94,6 +96,9 @@ sub do_import_index ($$@) {
                 my $nproc = $self->detect_nproc;
                 $j = $nproc if $j > $nproc;
         }
+        if ($lei->{opt}->{'new-only'} && (!$net || !$net->{imap_order})) {
+                $lei->err('# --new-only is only for IMAP');
+        }
         my $ops = {};
         $lei->{auth}->op_merge($ops, $self) if $lei->{auth};
         $self->{-wq_nr_workers} = $j // 1; # locked