lei_mirror: use fetch.hideRefs to speed up connectivity check

`git fetch' runs an expensive connectivity check against all
refs, which is unnecessarily expensive for incremental fetches
on RAM-constrained systems.

This depends on the proposal to support `fetch.hideRefs' for `git fetch':
https://public-inbox.org/git/20230212090426.M558990@dcvr/

diff --git a/lib/PublicInbox/LeiMirror.pm b/lib/PublicInbox/LeiMirror.pm
index 4dedac9b36c5be711a19844d3b471806726712ef..95486f37a3fc1bb7cd481365c8695fdfe2983544 100644 (file)
--- a/lib/PublicInbox/LeiMirror.pm
+++ b/lib/PublicInbox/LeiMirror.pm
@@ -407,13 +407,13 @@ sub fgrp_fetch_all {
        while (my ($osdir, $fgrp_old_new) = each %$todo) {
                my $f = "$osdir/config";
                return if !keep_going($self);
-               my ($fgrpv, $new) = @$fgrp_old_new;
-               @$fgrpv = sort { $b->{-sort} <=> $a->{-sort} } @$fgrpv;
-               push @$fgrpv, @$new; # $new is ordered by references
-
+               my ($old, $new) = @$fgrp_old_new;
+               @$old = sort { $b->{-sort} <=> $a->{-sort} } @$old;
+               # $new is ordered by {references}
                my $cmd = ['git', "--git-dir=$osdir", qw(config -f), $f ];
-               # clobber group from previous run atomically
-               for ("remotes.$grp") { # TODO: hideRefs
+
+               # clobber settings from previous run atomically
+               for ("remotes.$grp", 'fetch.hideRefs') {
                        my $c = [ @$cmd, '--unset-all', $_ ];
                        $self->{lei}->qerr("# @$c");
                        next if $self->{dry_run};
@@ -424,7 +424,7 @@ sub fgrp_fetch_all {
 
                # permanent configs:
                my $cfg = PublicInbox::Config->git_config_dump($f);
-               for my $fgrp (@$fgrpv) {
+               for my $fgrp (@$old, @$new) {
                        my $u = $fgrp->{-uri} // die 'BUG: no {-uri}';
                        my $rn = $fgrp->{-remote} // die 'BUG: no {-remote}';
                        for ("url=$u", "fetch=+refs/*:refs/remotes/$rn/*",
@@ -446,14 +446,24 @@ sub fgrp_fetch_all {
                                or die "open($f.lock): $!";
                        open my $fh, '>>', $f or die "open(>>$f): $!";
                        $fh->autoflush(1);
-                       my $buf = join('', "[remotes]\n",
-                               map { "\t$grp = $_->{-remote}\n" } @$fgrpv);
+                       my $buf = '';
+                       if (@$old) {
+                               $buf = "[fetch]\n\thideRefs = refs\n";
+                               $buf .= join('', map {
+                                       "\thideRefs = !refs/remotes/" .
+                                               "$_->{-remote}/\n";
+                               } @$old);
+                       }
+                       $buf .= join('', "[remotes]\n",
+                               (map { "\t$grp = $_->{-remote}\n" } @$old),
+                               (map { "\t$grp = $_->{-remote}\n" } @$new));
                        print $fh $buf or die "print($f): $!";
                        close $fh or die "close($f): $!";
                        unlink("$f.lock") or die "unlink($f.lock): $!";
                }
-               $cmd = [ @git, "--git-dir=$osdir", @fetch, $grp ];
-               my $end = PublicInbox::OnDestroy->new($$, \&fgrpv_done, $fgrpv);
+               $cmd  = [ @git, "--git-dir=$osdir", @fetch, $grp ];
+               push @$old, @$new;
+               my $end = PublicInbox::OnDestroy->new($$, \&fgrpv_done, $old);
                start_cmd($self, $cmd, $opt, $end);
        }
 }