t: switch $_z40 to $ZERO_OID

diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index 482112ca339f05fc31e6f9c2c6168971a1121e87..0dbf7d5b4bb489a55ec7a85f0e140e2ab43a102c 100755 (executable)
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -1523,7 +1523,7 @@ test_expect_success 'cover letter auto user override' '
 test_expect_success 'format-patch --zero-commit' '
        git format-patch --zero-commit --stdout v2..v1 >patch2 &&
        grep "^From " patch2 | sort | uniq >actual &&
-       echo "From $_z40 Mon Sep 17 00:00:00 2001" >expect &&
+       echo "From $ZERO_OID Mon Sep 17 00:00:00 2001" >expect &&
        test_cmp expect actual
 '