Support custom DOCKER_CONFIG dir

[hmnd]

Summary

Allow running docker commands with a custom DOCKER_CONFIG per stack

Detailed description

The only way to login with more than one account per registry is to use a separate docker config dir per account. It's possible to tell docker and docker compose which config to use by setting the DOCKER_CONFIG env var for the shell docker compose is run within.

I would like for it to be possible to provide a different DOCKER_CONFIG per stack, so that I may pull images from private repos using different credentials.

Alternatives considered

Considered using .env, but docker ignores it.

[mstrhakr]

I like this idea as I also use a few private repos, mostly at work though. I am looking into this, but adding some kind of credential manager seems to be the best UX for this, then you would select which credential to use in the stack settings. Do you have any other ideas on how this should work?

[hmnd]

Credential manager would be quite nice! My original thought was just to allow manually setting the higher-level DOCKER_CONFIG env var, as I didn't know how far you'd want to take it!