Background: https://github.com/docker-library/docker/pull/12 Executor: docker --- Some images needs entrypoint arguments instead of environment variables to configure the service. Unfortunately this is needed for the `docker:dind` image. So when an user wants to pass a custom docker registry mirror, he needs at the moment an [patched version of this image](https://hub.docker.com/r/jack12816/docker/) to support an environment variable. The current approach to configure services looks like this: ``` job: services: - postgres:9.5 - redis:3.2 ``` I would like to see an ability to configure starting options like `docker-compose.yml` supports. It could look like this: ``` job: services: "docker:dind": command: --registry-mirror=http://mymirror:6000 ``` There could be also an `environment` array node to configure specific environment variables only for this service. (To stop pollution on environment variables on all related containers) ``` job: services: "docker:dind": command: --registry-mirror=http://mymirror:6000 "postgres:9.5": environment: POSTGRES_USER: postgres POSTGRES_PASSWORD: postgres ``` What do you think about it?