Add dockerFile option

[cgrimal]

Define the dockerFile option that is mutually exclusive with the dockerImage option.

If dockerFile is provided, it must be the name of the Dockerfile file, placed in the current directory.
When building requirements, a Docker image is built based on the provided Dockerfile, and requirements are then built using this image.

Limitations:

• built every time (even if image exists and Dockerfile has not changed)
• Dockerfile can have any name but MUST be in the current directory

Open Questions:

• If dockerizePip is false but any docker related options are provided, no warning are raised. Should I fix it?
• Are these limitations an issue? Do you have ideas how to improve on them?

Related issues:

• Closes Option to package with supplied Dockerfile #114
• Closes Bootstrap numpy installation #126
• Closes Need to install Python module that have system dependencies #101
• Closes Implement a prereqCmd option for installing system deps #103

[dschep]

Magnifique! I added 2 more related issues to your description 😄

Limitations:

• build every time is fine since docker's caching should make it fast if nothing has changed.
• huh. Is that a docker build -f limitation?

Open questions:

• A warning in that scenario would be great 👍
• I won't reject this because of those limitations, but I'm not sure how to mitigate them either.

[dschep]

Could you move this docker build logic to a new lib/docker.js module?

[cgrimal]

Thanks for your feedback @dschep!

• It is indeed possible to place the Dockerfile in a subfolder. I updated the README. That said, you can't have it elsewhere, or Docker will raise a "The Dockerfile must be within the build context (.)" error. FYI, A working solution in command-line is to do docker build -t sls-py-reqs-custom - < /path/to/Dockerfile but I can't make it work with spawnSync. I tried using the input option but I couldn't make it work.

• I added a warning (not exiting the process) if one of the docker related option is provided with dockerizePip set to false.

• I moved some of the docker logic to a dedicated lib/docker.js module.

Let me know what you think.

[dschep]

Looks fantastic! I'll make a release after work when I can test it.