print usage

mirai-console/src/main/kotlin/net/mamoe/mirai/console/MiraiConsole.kt

@@ -159,7 +159,7 @@ object MiraiConsole {
                     commandStr = "/$commandStr"
                 }
                 if (!CommandManager.runCommand(command.sender, commandStr)) {
-                    logger("未知指令 $commandStr")
+                    command.sender.sendMessage("未知指令 $commandStr")
                 }
             }
         }

mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/Command.kt

@@ -74,6 +74,8 @@ object CommandManager {
                     )
                 ) {
                     PluginManager.onCommand(this, args)
+                } else {
+                    sender.sendMessage(this.usage)
                 }
             } catch (e: Exception) {
                 sender.sendMessage("在运行指令时出现了未知错误")