t5550: require REFFILES

The dumb HTTP protocol exposes ref storage details as part of the protocol,
so it only works with the FILES refstorage backend

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5550-http-fetch-dumb.sh

@@ -5,6 +5,13 @@ GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
+
+if test_have_prereq !REFFILES
+then
+	skip_all='skipping test; dumb HTTP protocol not supported with reftable.'
+	test_done
+fi
+
 . "$TEST_DIRECTORY"/lib-httpd.sh
 start_httpd