For me, I don't define any variables via the cli, i put them all in the docker-compose.yml or accompanying .env file, that way it's a simple `docker-compose up` to deploy. Then I can track these files via git, and deploy to remote docker hosts using docker-machine, which effectively sets the DOCKER_HOST env var.

While I haven't used it personally, there is [0] Watchtower which aims to automate updating docker containers.

[0] https://github.com/containrrr/watchtower