Initialize container volumes with local files

[martin-helmich]

Context

Oftentimes, container deployments might need to be initialized with a certain set of local files.

Common examples include application-specific configuration files.

Currently, providing these files (especially in a freshly initialized project) is cumbersome, and consists of the following steps:

1. Provide an empty dummy app or container (e.g. static file app, or a busybox container)
2. Connect to that app, synchronize files (rsync or scp) into the project's /files directory or into a volume
3. Then mount that directory into the actual container.
4. Remove the temporary dummy app/container

Proposal

Imperative workflow (using container run)

Proposal: Add an additional volume mirror command that initializes a new volume that is automatically initialized from a local directory (alternatively, add a --initialize-from flag to the volume create command:

# alternative #1
user@local $ mw volume create config
user@local $ mw volume mirror ./config config

# alternative #2
user@local $ mw volume create --initialize-from=./config config

# usage
user@local $ mw container run -v config:/etc/config [...]

Declarative workflow (using stack deploy)

Proposal: Use docker-compose syntax (combined with a custom driver) to configure volume initialization:

volumes:
  config:
    driver: local-sync
    driver_opts:
      source: ./config

[martin-helmich]

/fyi @gandie

[gandie]

Well i like both notations a lot.

I think we could start with imperative workflow and work towards the declarative one. If i get this correctly, the implementation steps needed in the imperative workflow can be reused in the declarative one when preparing the stack request.