Improve the mode of mounting submit_cs source code (preferably via an ENV variable)

[garethgeorge]

• Mounting submit_cs source code
  • https://docs.docker.com/compose/environment-variables/
    web:
    image: "webapp:${TAG}”
  • This will allow an arbitrary directory for the source code to be mounted into the container and, in fact, even built into the container.
  • My proposed build process then becomes:
    • git ssh://github.com/submit-cs/ /submit/runtime/submit_src
    • The mount script should then pip install from this directory,
    • If the container is mounted with the new source code mounted over top of this directory then the container will automatically use the local copy of the code instead
  • This has the advantage of unifying the code that deploys master and the code that mounts local development code to be roughly the same startup process. Yep yep
  • An alternative would simply be to check if anything is mounted at a specific path and switch the launch strategy (pip install from master vs just pip install from local source) depending on that.