Add help screen to the command on wrong argument

exporter/main.php

@@ -107,6 +107,31 @@
 
 		} break;
 
+		/* (4) Help message
+		---------------------------------------------------------*/
+		default: {
+
+			echo "xfw: xdrm framework\n";
+			echo "\n";
+			echo "COMMANDS\n";
+			echo "\tinit\n";
+			echo "\t\tInitialize a new framework environment.\n";
+			echo "\n";
+			echo "\tpackages\n";
+			echo "\t\tList all available packages and its versions.\n";
+			echo "\n";
+			echo "\tinstall @pkg_name:@version\n";
+			echo "\t\tAdd the version @version of the package @pkg_name to the environment.\n";
+			echo "\n";
+			echo "\tremove @pkg_name\n";
+			echo "\t\tRemove the package @pkg_name from the environment.\n";
+			echo "\n";
+			echo "\tbuild @root_path\n";
+			echo "\t\tBuild from the environment at the location @root_path.\n";
+			echo "\n";
+
+		} break;
+
 	}