t2025: add a test to make sure grafts is working from a linked checkout

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t2025-checkout-to.sh

diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index 4bd1df4..eddd325 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -96,4 +96,22 @@
 	)
 '
 
+test_expect_success 'checkout with grafts' '
+	test_when_finished rm .git/info/grafts &&
+	test_commit abc &&
+	SHA1=`git rev-parse HEAD` &&
+	test_commit def &&
+	test_commit xyz &&
+	echo "`git rev-parse HEAD` $SHA1" >.git/info/grafts &&
+	cat >expected <<-\EOF &&
+	xyz
+	abc
+	EOF
+	git log --format=%s -2 >actual &&
+	test_cmp expected actual &&
+	git checkout --detach --to grafted master &&
+	git --git-dir=grafted/.git log --format=%s -2 >actual &&
+	test_cmp expected actual
+'
+
 test_done