commit-graph.c: ensure graph layers respect core.sharedRepository

Non-layered commit-graphs use 'adjust_shared_perm' to make the
commit-graph file readable (or not) to a combination of the user, group,
and others.

Call 'adjust_shared_perm' for split-graph layers to make sure that these
also respect 'core.sharedRepository'. The 'commit-graph-chain' file
already respects this configuration since it uses
'hold_lock_file_for_update' (which calls 'adjust_shared_perm' eventually
in 'create_tempfile_mode').

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit-graph.c

@@ -1386,6 +1386,12 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
 			return -1;
 		}
 
+		if (adjust_shared_perm(ctx->graph_name)) {
+			error(_("unable to adjust shared permissions for '%s'"),
+			      ctx->graph_name);
+			return -1;
+		}
+
 		f = hashfd(fd, ctx->graph_name);
 	} else {
 		hold_lock_file_for_update_mode(&lk, ctx->graph_name,

t/t5324-split-commit-graph.sh

@@ -36,6 +36,10 @@ graph_read_expect() {
 	test_cmp expect output
 }
 
+test_expect_success POSIXPERM 'tweak umask for modebit tests' '
+	umask 022
+'
+
 test_expect_success 'create commits and write commit-graph' '
 	for i in $(test_seq 3)
 	do
@@ -351,4 +355,22 @@ test_expect_success 'split across alternate where alternate is not split' '
 	test_cmp commit-graph .git/objects/info/commit-graph
 '
 
+while read mode modebits
+do
+	test_expect_success POSIXPERM "split commit-graph respects core.sharedrepository $mode" '
+		rm -rf $graphdir $infodir/commit-graph &&
+		git reset --hard commits/1 &&
+		test_config core.sharedrepository "$mode" &&
+		git commit-graph write --split --reachable &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 1 graph-files &&
+		echo "$modebits" >expect &&
+		test_modebits $graphdir/graph-*.graph >actual &&
+		test_cmp expect actual
+	'
+done <<\EOF
+0666 -r--r--r--
+0600 -r--------
+EOF
+
 test_done