anchor.diff:  CMD /usr/bin/ruby /etc/mtconnect/simulator/run_scenario.rb -l \
     /etc/mtconnect/simulator/VMC-3Axis-Log.txt & \
     cd /etc/mtconnect/simulator && agent debug agent.cfg
  +
  +# ---------------------------------------------------------------------
  +# note
  +# ---------------------------------------------------------------------
  +
  +# After setup, the dirs look like this -
  +#
  +# /usr/local/bin
  +#  |-- agent - the cppagent application
  +#
  +# /etc/mtconnect
  +#  |-- schemas - xsd files
  +#  |-- simulator - agent.cfg, simulator.rb, vmc-3axis.xml, log.txt
  +#  |-- styles - Streams.xsl, Streams.css, favicon.ico
  +#
  +# the default simulator/agent.cfg has -
  +#   Devices = ../simulator/VMC-3Axis.xml
  +#   Files { styles { Path = ../styles } }
  +# see https://github.com/mtconnect/cppagent/blob/master/simulator/agent.cfg
  
positive.code: # so can clone the private mtconnect cppagent_dev repo.
  # keep it out of the github repo with .gitignore.
  # this sets up a file with the contents accessible at /run/secrete/access_token.
  # see below at 
  #   git clone https://$(cat /run/secrets/access_token)@github.com...
  
  # ---------------------------------------------------------------------
  # os
  
negative.code:   -o run_tests=False \
    -o with_ruby=$WITH_RUBY
  
  # limit cpus so don't run out of memory on local machine
  # symptom: get error - "c++: fatal error: Killed signal terminated program cc1plus"
  ENV CONAN_CPU_COUNT=1
  
  # compile source (~20mins - 3hrs for qemu)
  RUN cd ~/agent && conan build . -bf build
  
  # ---------------------------------------------------------------------
  # release
  