t1001: use $ZERO_OID

Use $ZERO_OID to make the test hash independent.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1091-sparse-checkout-builtin.sh

@@ -369,7 +369,7 @@ test_expect_success 'sparse-checkout (init|set|disable) warns with unmerged stat
 	git clone repo unmerged &&
 
 	cat >input <<-EOF &&
-	0 0000000000000000000000000000000000000000	folder1/a
+	0 $ZERO_OID	folder1/a
 	100644 $(git -C unmerged rev-parse HEAD:folder1/a) 1	folder1/a
 	EOF
 	git -C unmerged update-index --index-info <input &&
@@ -396,7 +396,7 @@ test_expect_success 'sparse-checkout reapply' '
 	echo dirty >tweak/deep/deeper2/a &&
 
 	cat >input <<-EOF &&
-	0 0000000000000000000000000000000000000000	folder1/a
+	0 $ZERO_OID	folder1/a
 	100644 $(git -C tweak rev-parse HEAD:folder1/a) 1	folder1/a
 	EOF
 	git -C tweak update-index --index-info <input &&