I'm putting together a Dockerfile that builds some custom ROS packages on top of a ROS Indigo installation in /opt/ros/indigo. How do I source this installation directory such that catkin_tools will know that my custom workspace is extending the ROS Indigo installation?

Here's my hacky attempt, which seems to be working:

RUN /bin/bash -c "source /opt/ros/indigo/setup.bash ;\
                  catkin init ;\
                  catkin config --cmake-args -DCMAKE_BUILD_TYPE=Release ;\
                  catkin build --no-status --no-summary --no-notify"

This results in the following output from catkin init:

Extending:             [env] /opt/ros/indigo

Is there a more elegant way of accomplishing this?

PS. I'm aware of ENTRYPOINT, but that's for when the container is run, not during docker build