support to pass ROBOT_INITIAL_POSE via argument, in addition to environment

[k-okada]

this allow user to write

    <include file="$(find pr2_gazebo)/launch/pr2_empty_world.launch">
	<arg name="world_name" value="$(arg world_name)" />
	<arg name="ROBOT_INITIAL_POSE" value="-x 0.75 -y 0 -z 0" />
    </include>

and it will not break current usage:

ROBOT_INITIAL_POSE="-x 0.75 -y 0 -z 0" roslaunch pr2_gazebo pr2_empty_world.lauch

[v4hn]

Does this really work?

pr2.launch uses pass_all_args, but the documentation of this argument (I'd never heard of it before) makes it sound like pr2.launch should at least define the argument and only forwarding it in <include> can be omitted. Otherwise launch file sanitizers will have a harder time figuring out whether arguments are actually used..

If that's just a misunderstanding on my end, feel free to merge.