[PATCH v2] lei import: support --new-only for IMAP

[Eric Wong <e@80x24.org>]

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.
---
 lib/PublicInbox/LEI.pm       | 2 +-
 lib/PublicInbox/LeiImport.pm | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 265b7047..beeb8b48 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -240,7 +240,7 @@ our %CMD = ( # sorted in order of importance/use:
 	 @c_opt ],
 'import' => [ 'LOCATION...|--stdin',
 	'one-time import/update from URL or filesystem',
-	qw(stdin| offset=i recursive|r exclude=s include|I=s jobs=s
+	qw(stdin| offset=i recursive|r exclude=s include|I=s jobs=s new-only
 	lock=s@ in-format|F=s kw! verbose|v+ incremental! mail-sync!),
 	qw(no-torsocks torsocks=s), PublicInbox::LeiQuery::curl_opt(), @c_opt ],
 'forget-mail-sync' => [ 'LOCATION...',
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