Add support for multiple docker-compose files

[happytomatoe]

Lets say you have docker-compose.yml, docker-compose.sandbox.yml and docker-compose.production.yml.So in your sandbox environment you run docker-compose -f docker-compose.yml - f docker-compose.sandbox.yml... Is it doable?

[bitbier]

As a workaround, you can simply just call docker-compose config command, so you could do something like:

docker-compose -f docker-compose.yml -f docker-compose.sandbox.yml config | container-transform -q -o <output_of_choice>