This commit adds a new protocol command to toggle protocol features

for a client connection. It works like the tag_mask and the associated
tagtypes command.

New commands:

- protocol
  Shows enabled protocol features.

- protocol available
  Show all available protocol features.

- protocol enable {feature...}
  Enables protocol features.

- protocol disable {feature...}
  Disables protocol features.

- protocol all
  Enables all available protocol features.

- protocol clear
  Disables all protocol features.

This commit adds also the first protocol feature.

hide_playlists_in_root
  Disables the listing of playlists in the root folder
  for the lsinfo command.

src/command/AllCommands.cxx

@@ -156,6 +156,7 @@ static constexpr struct command commands[] = {
 	{ "previous", PERMISSION_PLAYER, 0, 0, handle_previous },
 	{ "prio", PERMISSION_PLAYER, 2, -1, handle_prio },
 	{ "prioid", PERMISSION_PLAYER, 2, -1, handle_prioid },
+	{ "protocol", PERMISSION_NONE, 0, -1, handle_protocol },
 	{ "random", PERMISSION_PLAYER, 1, 1, handle_random },
 	{ "rangeid", PERMISSION_ADD, 2, 2, handle_rangeid },
 	{ "readcomments", PERMISSION_READ, 1, 1, handle_read_comments },

src/command/ClientCommands.cxx

@@ -109,3 +109,67 @@ handle_tagtypes(Client &client, Request request, Response &r)
 		return CommandResult::ERROR;
 	}
 }
+
+static ProtocolFeature
+ParseProtocolFeature(Request request)
+{
+	if (request.empty())
+		throw ProtocolError(ACK_ERROR_ARG, "Not enough arguments");
+
+	ProtocolFeature result = ProtocolFeature::None();
+
+	for (const char *name : request) {
+		auto type = protocol_feature_parse_i(name);
+		if (type == PF_NUM_OF_ITEM_TYPES)
+			throw ProtocolError(ACK_ERROR_ARG, "Unknown protcol feature");
+
+		result |= type;
+	}
+
+	return result;
+}
+
+CommandResult
+handle_protocol(Client &client, Request request, Response &r)
+{
+	if (request.empty()) {
+		protocol_features_print(client, r);
+		return CommandResult::OK;
+	}
+
+	const char *cmd = request.shift();
+	if (StringIsEqual(cmd, "all")) {
+		if (!request.empty()) {
+			r.Error(ACK_ERROR_ARG, "Too many arguments");
+			return CommandResult::ERROR;
+		}
+
+		client.AllProtocolFeatures();
+		return CommandResult::OK;
+	} else if (StringIsEqual(cmd, "clear")) {
+		if (!request.empty()) {
+			r.Error(ACK_ERROR_ARG, "Too many arguments");
+			return CommandResult::ERROR;
+		}
+
+		client.ClearProtocolFeatures();
+		return CommandResult::OK;
+	} else if (StringIsEqual(cmd, "enable")) {
+		client.SetProtocolFeatures(ParseProtocolFeature(request), true);
+		return CommandResult::OK;
+	} else if (StringIsEqual(cmd, "disable")) {
+		client.SetProtocolFeatures(ParseProtocolFeature(request), false);
+		return CommandResult::OK;
+	} else if (StringIsEqual(cmd, "available")) {
+		if (!request.empty()) {
+			r.Error(ACK_ERROR_ARG, "Too many arguments");
+			return CommandResult::ERROR;
+		}
+
+		protocol_features_print_all(r);
+		return CommandResult::OK;
+	} else {
+		r.Error(ACK_ERROR_ARG, "Unknown sub command");
+		return CommandResult::ERROR;
+	}
+}

src/command/ClientCommands.hxx

@@ -25,4 +25,7 @@ handle_password(Client &client, Request request, Response &response);
 CommandResult
 handle_tagtypes(Client &client, Request request, Response &response);
 
+CommandResult
+handle_protocol(Client &client, Request request, Response &response);
+
 #endif

src/command/OtherCommands.cxx

@@ -160,7 +160,7 @@ handle_lsinfo_relative(Client &client, Response &r, const char *uri)
 	(void)client;
 #endif
 
-	if (isRootDirectory(uri)) {
+	if (!client.ProtocolFeatureEnabled(PF_HIDE_PLAYLISTS_IN_ROOT) && isRootDirectory(uri)) {
 		try {
 			print_spl_list(r, ListPlaylistFiles());
 		} catch (...) {