fetch: support --exit-code switch

As noted in the new manpage entry, this is useful for avoiding
public-inbox-index invocations when there's nothing to update.
We use 127 to match "grok-pull", and also because it doesn't
conflict with any of the current curl(1) exit codes.

1 files changed, 20 insertions, 1 deletions

diff --git a/lib/PublicInbox/Fetch.pm b/lib/PublicInbox/Fetch.pm
index 9ea55e9d..0539fe50 100644
--- a/lib/PublicInbox/Fetch.pm
+++ b/lib/PublicInbox/Fetch.pm
@@ -75,12 +75,22 @@ sub do_manifest ($$$) {
                 my $t1 = $cur->{modified} // next;
                 delete($mdiff->{$k}) if $f0 eq $f1 && $t0 == $t1;
         }
-        return unless keys %$mdiff;
+        unless (keys %$mdiff) {
+                $lei->child_error(127 << 8) if $lei->{opt}->{'exit-code'};
+                return;
+        }
         my (undef, $v1_path, @v2_epochs) =
                 PublicInbox::LeiMirror::deduce_epochs($mdiff, $ibx_uri->path);
         [ 200, $v1_path, \@v2_epochs, $muri, $ft, $mf ];
 }
 
+sub get_fingerprint2 {
+        my ($git_dir) = @_;
+        require Digest::SHA;
+        my $rd = popen_rd([qw(git show-ref)], undef, { -C => $git_dir });
+        Digest::SHA::sha256(do { local $/; <$rd> });
+}
+
 sub do_fetch {
         my ($cls, $lei, $cd) = @_;
         my $ibx_ver;
@@ -136,11 +146,14 @@ EOM
         }
         # n.b. this expects all epochs are from the same host
         my $torsocks = $lei->{curl}->torsocks($lei, $muri);
+        my $fp2 = $lei->{opt}->{'exit-code'} ? [] : undef;
+        my $xit = 127;
         for my $d (@git_dir) {
                 my $cmd;
                 my $opt = {}; # for spawn
                 if (-d $d) {
                         $opt->{-C} = $d;
+                        $fp2->[0] = get_fingerprint2($d) if $fp2;
                         $cmd = [ @$torsocks, fetch_cmd($lei, $opt) ];
                 } else {
                         my $e_uri = $ibx_uri->clone;
@@ -152,6 +165,7 @@ EOM
                                 PublicInbox::LeiMirror::clone_cmd($lei, $opt),
                                 $$e_uri, $d];
                         push @new_epoch, substr($epath, 5, -4) + 0;
+                        $xit = 0;
                 }
                 my $cerr = PublicInbox::LeiMirror::run_reap($lei, $cmd, $opt);
                 # do not bail on clone failure if we didn't have a manifest
@@ -159,6 +173,10 @@ EOM
                         $lei->child_error($cerr, "@$cmd failed");
                         return;
                 }
+                if ($fp2 && $xit) {
+                        $fp2->[1] = get_fingerprint2($d);
+                        $xit = 0 if $fp2->[0] ne $fp2->[1];
+                }
         }
         for my $i (@new_epoch) { $mg->epoch_cfg_set($i) }
         if ($ft) {
@@ -166,6 +184,7 @@ EOM
                 rename($fn, $mf) or die "E: rename($fn, $mf): $!\n";
                 $ft->unlink_on_destroy(0);
         }
+        $lei->child_error($xit << 8) if $fp2 && $xit;
 }
 
 1;