lei_mirror: avoid dir/file conflicts in update-ref

Using the files ref backend for git, `delete' and `create'
operations for `update-ref --stdin' need to be processed in
separate transactions to avoid conflicts in cases where a file
becomes a directory (or presumably, vice versa).

1 files changed, 35 insertions, 12 deletions

diff --git a/lib/PublicInbox/LeiMirror.pm b/lib/PublicInbox/LeiMirror.pm
index afe12bb3..d959b6b6 100644
--- a/lib/PublicInbox/LeiMirror.pm
+++ b/lib/PublicInbox/LeiMirror.pm
@@ -288,6 +288,19 @@ sub upr { # feed `git update-ref --stdin -z' verbosely
         print $w "$op ", join("\0", @rest, '') or die "print(w): $!";
 }
 
+sub start_update_ref {
+        my ($fgrp) = @_;
+        pipe(my ($r, $w)) or die "pipe: $!";
+        my $cmd = [ 'git', "--git-dir=$fgrp->{cur_dst}",
+                qw(update-ref --stdin -z) ];
+        my $pack = PublicInbox::OnDestroy->new($$, \&satellite_done, $fgrp);
+        start_cmd($fgrp, $cmd, { 0 => $r, 2 => $fgrp->{lei}->{2} }, $pack);
+        close $r or die "close(r): $!";
+        $fgrp->{dry_run} ? undef : $w;
+}
+
+sub upref_warn { warn "E: close(update-ref --stdin): $! (need git 1.8.5+)\n" }
+
 sub fgrp_update {
         my ($fgrp) = @_;
         return if !keep_going($fgrp);
@@ -299,14 +312,9 @@ sub fgrp_update {
         close $srcfh;
         my %dst = map { chomp; split(/\0/) } (<$dstfh>);
         close $dstfh;
-        pipe(my ($r, $w)) or die "pipe: $!";
-        my $cmd = [ 'git', "--git-dir=$fgrp->{cur_dst}",
-                qw(update-ref --stdin -z) ];
+        my $w = start_update_ref($fgrp) or return;
         my $lei = $fgrp->{lei};
-        my $pack = PublicInbox::OnDestroy->new($$, \&satellite_done, $fgrp);
-        start_cmd($fgrp, $cmd, { 0 => $r, 2 => $lei->{2} }, $pack);
-        close $r or die "close(r): $!";
-        return if $fgrp->{dry_run};
+        my $ndel;
         for my $ref (keys %dst) {
                 my $new = delete $src{$ref};
                 my $old = $dst{$ref};
@@ -315,18 +323,33 @@ sub fgrp_update {
                                 upr($lei, $w, 'update', $ref, $new, $old);
                 } else {
                         upr($lei, $w, 'delete', $ref, $old);
+                        ++$ndel;
                 }
         }
-        while (my ($ref, $oid) = each %src) {
-                upr($lei, $w, 'create', $ref, $oid);
+        # git's ref files backend doesn't allow directory/file conflicts
+        # between `delete' and `create' ops:
+        if ($ndel && scalar(keys %src)) {
+                $fgrp->{-create_refs} = \%src;
+        } else {
+                while (my ($ref, $oid) = each %src) {
+                        upr($lei, $w, 'create', $ref, $oid);
+                }
         }
-        close($w) or warn "E: close(update-ref --stdin): $! (need git 1.8.5+)\n";
+        close($w) or upref_warn();
 }
 
 sub satellite_done {
         my ($fgrp) = @_;
-        pack_refs($fgrp, $fgrp->{cur_dst});
-        run_puh($fgrp);
+        if (my $create = delete $fgrp->{-create_refs}) {
+                my $w = start_update_ref($fgrp) or return;
+                while (my ($ref, $oid) = each %$create) {
+                        upr($fgrp->{lei}, $w, 'create', $ref, $oid);
+                }
+                close($w) or upref_warn();
+        } else {
+                pack_refs($fgrp, $fgrp->{cur_dst});
+                run_puh($fgrp);
+        }
 }
 
 sub pack_refs {