stash -p: demonstrate failure of split with mixed y/n

Signed-off-by: NMatthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t3904-stash-patch.sh

@@ -81,4 +81,27 @@ test_expect_success 'none of this moved HEAD' '
 	verify_saved_head
 '
 
+test_expect_failure 'stash -p with split hunk' '
+	git reset --hard &&
+	cat >test <<-\EOF &&
+	aaa
+	bbb
+	ccc
+	EOF
+	git add test &&
+	git commit -m "initial" &&
+	cat >test <<-\EOF &&
+	aaa
+	added line 1
+	bbb
+	added line 2
+	ccc
+	EOF
+	printf "%s\n" s n y q |
+	test_might_fail git stash -p 2>error &&
+	! test_must_be_empty error &&
+	grep "added line 1" test &&
+	! grep "added line 2" test
+'
+
 test_done