transport: convert get_refs_list to take a list of ref prefixes

Convert the 'struct transport' virtual function 'get_refs_list()' to
optionally take an argv_array of ref prefixes.  When communicating with
a server using protocol v2 these ref prefixes can be sent when
requesting a listing of their refs allowing the server to filter the
refs it sends based on the sent prefixes.  This list will be ignored
when not using protocol v2.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

transport-helper.c

@@ -1026,7 +1026,8 @@ static int has_attribute(const char *attrs, const char *attr) {
 	}
 }
 
-static struct ref *get_refs_list(struct transport *transport, int for_push)
+static struct ref *get_refs_list(struct transport *transport, int for_push,
+				 const struct argv_array *ref_prefixes)
 {
 	struct helper_data *data = transport->data;
 	struct child_process *helper;
@@ -1039,7 +1040,7 @@ static struct ref *get_refs_list(struct transport *transport, int for_push)
 
 	if (process_connect(transport, for_push)) {
 		do_take_over(transport);
-		return transport->vtable->get_refs_list(transport, for_push);
+		return transport->vtable->get_refs_list(transport, for_push, ref_prefixes);
 	}
 
 	if (data->push && for_push)

transport-internal.h

@@ -3,6 +3,7 @@
 
 struct ref;
 struct transport;
+struct argv_array;
 
 struct transport_vtable {
 	/**
@@ -17,11 +18,19 @@ struct transport_vtable {
 	 * the transport to try to share connections, for_push is a
 	 * hint as to whether the ultimate operation is a push or a fetch.
 	 *
+	 * If communicating using protocol v2 a list of prefixes can be
+	 * provided to be sent to the server to enable it to limit the ref
+	 * advertisement.  Since ref filtering is done on the server's end, and
+	 * only when using protocol v2, this list will be ignored when not
+	 * using protocol v2 meaning this function can return refs which don't
+	 * match the provided ref_prefixes.
+	 *
 	 * If the transport is able to determine the remote hash for
 	 * the ref without a huge amount of effort, it should store it
 	 * in the ref's old_sha1 field; otherwise it should be all 0.
 	 **/
-	struct ref *(*get_refs_list)(struct transport *transport, int for_push);
+	struct ref *(*get_refs_list)(struct transport *transport, int for_push,
+				     const struct argv_array *ref_prefixes);
 
 	/**
 	 * Fetch the objects for the given refs. Note that this gets

transport.c

@@ -72,7 +72,9 @@ struct bundle_transport_data {
 	struct bundle_header header;
 };
 
-static struct ref *get_refs_from_bundle(struct transport *transport, int for_push)
+static struct ref *get_refs_from_bundle(struct transport *transport,
+					int for_push,
+					const struct argv_array *ref_prefixes)
 {
 	struct bundle_transport_data *data = transport->data;
 	struct ref *result = NULL;
@@ -189,7 +191,8 @@ static int connect_setup(struct transport *transport, int for_push)
 	return 0;
 }
 
-static struct ref *get_refs_via_connect(struct transport *transport, int for_push)
+static struct ref *get_refs_via_connect(struct transport *transport, int for_push,
+					const struct argv_array *ref_prefixes)
 {
 	struct git_transport_data *data = transport->data;
 	struct ref *refs = NULL;
@@ -204,7 +207,8 @@ static struct ref *get_refs_via_connect(struct transport *transport, int for_pus
 	data->version = discover_version(&reader);
 	switch (data->version) {
 	case protocol_v2:
-		get_remote_refs(data->fd[1], &reader, &refs, for_push, NULL);
+		get_remote_refs(data->fd[1], &reader, &refs, for_push,
+				ref_prefixes);
 		break;
 	case protocol_v1:
 	case protocol_v0:
@@ -250,7 +254,7 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.update_shallow = data->options.update_shallow;
 
 	if (!data->got_remote_heads)
-		refs_tmp = get_refs_via_connect(transport, 0);
+		refs_tmp = get_refs_via_connect(transport, 0, NULL);
 
 	switch (data->version) {
 	case protocol_v2:
@@ -568,7 +572,7 @@ static int git_transport_push(struct transport *transport, struct ref *remote_re
 	int ret = 0;
 
 	if (!data->got_remote_heads)
-		get_refs_via_connect(transport, 1);
+		get_refs_via_connect(transport, 1, NULL);
 
 	memset(&args, 0, sizeof(args));
 	args.send_mirror = !!(flags & TRANSPORT_PUSH_MIRROR);
@@ -1028,7 +1032,7 @@ int transport_push(struct transport *transport,
 		if (check_push_refs(local_refs, refspec_nr, refspec) < 0)
 			return -1;
 
-		remote_refs = transport->vtable->get_refs_list(transport, 1);
+		remote_refs = transport->vtable->get_refs_list(transport, 1, NULL);
 
 		if (flags & TRANSPORT_PUSH_ALL)
 			match_flags |= MATCH_REFS_ALL;
@@ -1137,7 +1141,7 @@ int transport_push(struct transport *transport,
 const struct ref *transport_get_remote_refs(struct transport *transport)
 {
 	if (!transport->got_remote_refs) {
-		transport->remote_refs = transport->vtable->get_refs_list(transport, 0);
+		transport->remote_refs = transport->vtable->get_refs_list(transport, 0, NULL);
 		transport->got_remote_refs = 1;
 	}