Investigate caching docker build images in build-ci repo

[CodeGat]

Docker Images don't seem to be caching very well when running GitHub actions. Potentially this could be because the base image (spack_packages) is constantly changing and therefore any images on top of it must be rebuilt form scratch.

Investigate possible solutions:

• Check if there are any caching options in the Github Actions syntax itself - https://docs.docker.com/build/cache/backends/gha/ and https://github.com/marketplace/actions/docker-layer-caching
• Make the environment setup (apt-get) it's own image, meaning it will be snapshotted and won't need to be rebuilt.
• Determine if there is a need for multiple image layers at all - could we just have an image with all of the models dependencies installed, and use spack activate <model_environment> as a build arg?
  • Pros: amalgamation into a single image and easy switching between dependencies with spack activate, potential for a bit more build caching
  • Cons: Every time a model (dependency) is changed, this large one will have to be rebuilt.

The ramblings of a madman...

[aidanheerdegen]

See also this issue #8

[CodeGat]

Closing as this issue is better described in #9 - the info here will be useful, however