t4200: demonstrate rerere segfault on specially crafted merge

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4200-rerere.sh

@@ -580,4 +580,33 @@ test_expect_success 'multiple identical conflicts' '
 	count_pre_post 0 0
 '
 
+test_expect_success 'setup simple stage 1 handling' '
+	test_create_repo stage_1_handling &&
+	(
+		cd stage_1_handling &&
+
+		test_seq 1 10 >original &&
+		git add original &&
+		git commit -m original &&
+
+		git checkout -b A master &&
+		git mv original A &&
+		git commit -m "rename to A" &&
+
+		git checkout -b B master &&
+		git mv original B &&
+		git commit -m "rename to B"
+	)
+'
+
+test_expect_failure 'test simple stage 1 handling' '
+	(
+		cd stage_1_handling &&
+
+		git config rerere.enabled true &&
+		git checkout A^0 &&
+		test_must_fail git merge B^0
+	)
+'
+
 test_done