This container helps resolve an issue with Container Optimized OS. The OS does not come with docker-compose, and instead expects users to use containerized docker-compose. However the official containerized docker-compose does not include docker-credential-gcr, which is needed to pull Docker images from a private Google Container Registry.
This container uses the official docker-compose as a base, and adds docker-credential-gcr. It can be used just like the normal containerized docker-compose, but can now access gcr.io.