promisor-remote: try accepted remotes before others in get_direct()

When a server advertises promisor remotes and the client accepts some of them, those remotes carry the server's intent: 'fetch missing objects preferably from here', and the client agrees with that for the remotes it accepts. However promisor_remote_get_direct() actually iterates over all promisor remotes in list order, which is the order they appear in the config files (except perhaps for the one appearing in the `extensions.partialClone` config variable which is tried last). This means an existing, but not accepted, promisor remote, could be tried before the accepted ones, which does not reflect the intent of the agreement between client and server. If the client doesn't care about what the server suggests, it should accept nothing and rely on its remotes as they are already configured. To better reflect the agreement between client and server, let's make promisor_remote_get_direct() try the accepted promisor remotes before the non-accepted ones. Concretely, let's extract a try_promisor_remotes() helper and call it twice from promisor_remote_get_direct(): - first with an `accepted_only=true` argument to try only the accepted remotes, - then with `accepted_only=false` to fall back to any remaining remote. Ensuring that accepted remotes are preferred will be even more important if in the future a mechanism is developed to allow the client to auto-configure remotes that the server advertises. This will in particular avoid fetching from the server (which is already configured as a promisor remote) before trying the auto-configured remotes, as these new remotes would likely appear at the end of the config file, and as the server might not appear in the `extensions.partialClone` config variable. Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>