What are best practices to override complete sections using docker-compose? The docker-compose.override contains:

volumes:
  - ./a:/path/to/a


The docker-compose:

volumes:
  - a:/path/to/a


When docker-compose up is run the override overwrite the ./a overwrites the a.

When a new volume is added to docker-compose, the override will try to mount is as well. 

docker-compose.override

volumes:
  - ./a:/path/to/a


The docker-compose:

volumes:
  - a:/path/to/a
  - b:/path/to/b


How to prevent that the override will use volumes that are defined in the docker-compose file?

When docker-compose.override contains

volumes:
  - a:/path/to/a
  - .b:/path/to/b


the b is still mounted...
According to this documentation it does not seem to be possible to override complete sections in docker-compose by using different docker-compose files.


  If both files are present on the same directory level, Compose
  combines the two files into a single configuration.
  
  The configuration in the docker-compose.override.yml file is applied
  over and in addition to the values in the docker-compose.yml file.