refs files-backend: assume cb->newlog if !EXPIRE_REFLOGS_DRY_RUN

It's not possible for "cb->newlog" to be NULL if
!EXPIRE_REFLOGS_DRY_RUN, since files_reflog_expire() would have
error()'d and taken the "goto failure" branch if it couldn't open the
file. By not using the "newlog" field private to "file-backend.c"'s
"struct expire_reflog_cb", we can move this verbosity logging to
"builtin/reflog.c" in a subsequent commit.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs/files-backend.c

@@ -3105,12 +3105,12 @@ static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
 
 	if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
 				   message, policy_cb)) {
-		if (!cb->newlog)
+		if (cb->flags & EXPIRE_REFLOGS_DRY_RUN)
 			printf("would prune %s", message);
 		else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
 			printf("prune %s", message);
 	} else {
-		if (cb->newlog) {
+		if (!(cb->flags & EXPIRE_REFLOGS_DRY_RUN)) {
 			fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
 				oid_to_hex(ooid), oid_to_hex(noid),
 				email, timestamp, tz, message);