Add note to ignore git clone warnings if path already exists (#645)

Author: AdamPettinger

doc/getting_started/getting_started.rst

@@ -39,7 +39,7 @@ Download Example Code
 
 To easily follow along with these tutorials, you will need a **ROBOT_moveit_config** package. The default demo robot is the Panda arm from Franka Emika. To get a working **panda_moveit_config** package, we recommend you install from source.
 
-Within your `catkin <http://wiki.ros.org/catkin>`_ workspace, download the tutorials as well as the ``panda_moveit_config`` package: ::
+Within your `catkin <http://wiki.ros.org/catkin>`_ workspace, download the tutorials as well as the ``panda_moveit_config`` package. You may safely ignore any :code:`git clone` errors saying the destination already exists: ::
 
   cd ~/ws_moveit/src
   git clone https://github.com/ros-planning/moveit_tutorials.git -b master