[PATCH 2/2] rev-parse: verify that commit looked up is not NULL

[Elijah Newren <newren@gmail.com>]

In commit 2122f8b963d4 ("rev-parse: Add support for the ^! and ^@ syntax",
2008-07-26), try_parent_shorthands() was introduced to parse the special
^! and ^@ syntax.  However, it did not check the commit returned from
lookup_commit_reference() before proceeding to use it.  If it is NULL,
bail early and notify the caller that this cannot be a valid revision
range.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 builtin/rev-parse.c          | 2 ++
 t/t6101-rev-parse-parents.sh | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 55c0b90441..4e9ba9641a 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -334,6 +334,8 @@ static int try_parent_shorthands(const char *arg)
 	}
 
 	commit = lookup_commit_reference(&oid);
+	if (!commit)
+		return 1;
 	if (exclude_parent &&
 	    exclude_parent > commit_list_count(commit->parents)) {
 		*dotdot = '^';
diff --git a/t/t6101-rev-parse-parents.sh b/t/t6101-rev-parse-parents.sh
index 7b1b2dbdf2..f91cc417bd 100755
--- a/t/t6101-rev-parse-parents.sh
+++ b/t/t6101-rev-parse-parents.sh
@@ -214,7 +214,7 @@ test_expect_success 'rev-list merge^-1x (garbage after ^-1)' '
 	test_must_fail git rev-list merge^-1x
 '
 
-test_expect_failure 'rev-parse $garbage^@ should not segfault' '
+test_expect_success 'rev-parse $garbage^@ should not segfault' '
 	git rev-parse ffffffffffffffffffffffffffffffffffffffff^@
 '
 
-- 
2.17.0.1025.g36b5c64692