Add option to include separate compose files under a namespace

[Tobias Trumm]

What is the problem you're trying to solve
I really like the new include top-level section, as it allowed me to split a huge docker-compose.yml file into smaller, more manageable ones. After splitting my docker-compose.yml, I found that many files contained the same service and volume definitions, just with different service names, volume names and environment variables.

I would like to include a single template.yml multiple times with different environment variables, but because service and volume names must be unique, this is not currently possible.

The following does not work

# docker-compose.yml
include:
  - path: template.yml
    env_file: env1.env
  - path: template.yml
    env_file: env2.env

# template.yml
services:
  template-service:
    image: someImage
    environment:
      VAR: ${VAR}
    volumes:
      - template-volume:/template-volume

volumes:
  template-volume

Describe the solution you'd like
I would like to propose a new additional field namespace. If namespace is present, the service and volume names of the included compose file will be prefixed with its value.

# docker-compose.yml
include:
  - path: template.yml
    env_file: env1.env
    namespace: template1
  - path: template.yml
    env_file: env2.env
    namespace: template2

Using the same template.yml file as above this would create the services template1-template-service, template2-template-service and the volumes template1-template-volume, template2-template-volume. I am not sure what a good separator between the namespace and the name would be, so I just used - in this example.

Additional context
I am not the first person who has tried to include the same compose file with a different set of env files. Over at the docker compose project someone has proposed a different solution that would allow for the interpolation of service/volume names using environment variables: docker/compose#10994

[Ali Chaudry]

Excellent idea! This would be a great addition. This could also help name mangling, such that included containers' auto-generated names are prefixed with their own project's name instead of the main (root) file's project name.