Subject: [PATCH 6/8] commit-graph verify: detect inability to read the graph

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 21 Feb 2019 23:37:51 +0100

Change "commit-graph verify" to error on open() failures other than
ENOENT. As noted in the third paragraph of 283e68c72f ("commit-graph:
add 'verify' subcommand", 2018-06-27) and the test it added it's
intentional that "commit-graph verify" doesn't error out when the file
doesn't exist.

But let's not be overly promiscuous in what we accept. If we can't
read the file for other reasons, e.g. permission errors, bad file
descriptor etc. we'd like to report an error to the user.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
---
 builtin/commit-graph.c  |  4 +++-
 t/t5318-commit-graph.sh | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index 8196fdbe9c..537fdfd0f0 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -62,8 +62,10 @@ static int graph_verify(int argc, const char **argv)
 
 	graph_name = get_commit_graph_filename(opts.obj_dir);
 	open_ok = open_commit_graph(graph_name, &fd, &st);
-	if (!open_ok)
+	if (!open_ok && errno == ENOENT)
 		return 0;
+	if (!open_ok)
+		die_errno(_("Could not open commit-graph '%s'"), graph_name);
 	graph = load_commit_graph_one_fd_st(fd, &st);
 	FREE_AND_NULL(graph_name);
 
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 0d012f55e5..1ee00fa333 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -400,6 +400,18 @@ corrupt_graph_and_verify() {
 
 }
 
+test_expect_success 'detect permission problem' '
+	corrupt_graph_setup &&
+	chmod 000 $objdir/info/commit-graph &&
+
+	# Skip as root, or in other cases (odd fs or OS) where a
+	# "chmod 000 file" does not yield EACCES on e.g. "cat file"
+	if ! test -r $objdir/info/commit-graph
+	then
+		corrupt_graph_verify "Could not open"
+	fi
+'
+
 test_expect_success 'detect too small' '
 	corrupt_graph_setup &&
 	echo "a small graph" >$objdir/info/commit-graph &&
-- 
2.21.0.rc0.258.g878e2cd30e