t1020-subdirectory: test alias expansion in a subdirectory

Add a test for alias expansion in a subdirectory of the worktree.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1020-subdirectory.sh

@@ -110,6 +110,14 @@ test_expect_success 'read-tree' '
 	)
 '
 
+test_expect_success 'alias expansion' '
+	(
+		git config alias.ss status &&
+		cd dir &&
+		git status &&
+		git ss
+	)
+'
 test_expect_success 'no file/rev ambiguity check inside .git' '
 	git commit -a -m 1 &&
 	(