Load all joints with controller_manager

edit

Following Gazebo tutorial about controlling joints from ROS, I realized that the joints are mentioned explicitely like in this example:

<launch>

  <!-- Load joint controller configurations from YAML file to parameter server -->
  <rosparam file="$(find rrbot_control)/config/rrbot_control.yaml" command="load"/>

  <!-- load the controllers -->
  <node name="controller_spawner" pkg="controller_manager" type="spawner" respawn="false"
    output="screen" ns="/rrbot" args="joint1_position_controller joint2_position_controller joint_state_controller"/>

  <!-- convert joint states to TF transforms for rviz, etc -->
  <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"
    respawn="false" output="screen">
    <remap from="/joint_states" to="/rrbot/joint_states" />
  </node>

</launch>

where joint1_position_controller, joint2_position_controller and joint_state_controller are the loaded controllers. I have around 50 joints to control and I don't want to put them manually in my launch file. How to tell the controller_manager to load all the controllers existing in the rrbot_control.yaml?