Default Dockerhub behavior

[guineveresaenger]

The Docker CLI treats Dockerhub as a special case, allowing local/short names for images such as username/imagename:tag to be implicitly tagged as docker.io/username/imagename:tag when attempting a docker push. As long as the user is logged in to Dockerhub, this image will be pushed.

In the context of a Pulumi program, emulating this behavior this could result in accidentally pushing an image to Dockerhub, and it would make sense from a security perspective to disallow this default behavior.

Now that it is possible to use host auth config implicitly, we need to decide what the behavior should be instead.

The most straightforward behavior would be to require setting Dockerhub explicitly:

• via a fully qualified image name: docker.io/username/imagename:tag
• or via setting the registry server field explicitly to use Dockerhub: docker.io OR index.docker.io/v1