t/t5538-push-shallow.sh: use the $( ... ) construct for command substitution

diff --git a/t/t3403-rebase-skip.sh b/t/t3403-rebase-skip.sh
index 3968020e648091e907fde6efe9aeb5ce66753670..1f5122b632fb9d7829e7b5f28c2a2971e9ea04e7 100755 (executable)
--- a/t/t3403-rebase-skip.sh
+++ b/t/t3403-rebase-skip.sh
@@ -67,7 +67,7 @@ test_expect_success 'rebase --skip with --merge' '
 '
 
 test_expect_success 'merge and reference trees equal' '
-       test -z "`git diff-tree skip-merge skip-reference`"
+       test -z "$(git diff-tree skip-merge skip-reference)"
 '
 
 test_expect_success 'moved back to branch correctly' '