transport: mark unused parameters in fetch_refs_from_bundle()

We don't look at the "to_fetch" or "nr_heads" parameters at all. At first glance this seems like a bug (or at least pessimisation), because it means we fetch more objects from the bundle than we actually need. But the bundle does not have any way of computing the set of reachable objects itself (we'd have to pull all of the objects out to walk them). And anyway, we've probably already paid most of the cost of grabbing the objects, since we must copy the bundle locally before accessing it. So it's perfectly reasonable for the bundle code to just pull everything into the local object store. Unneeded objects can be dropped later via gc, etc. But we should mark these unused parameters as such to avoid the wrath of -Wunused-parameter. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>