The docker help was consulted:
Usage: docker [OPTIONS] COMMANDA self-sufficient runtime for containersOptions: --config string Location of client config files (default "/home/ben/.docker") -c, --context string Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default context set with "docker context use") -D, --debug Enable debug mode -H, --host list Daemon socket(s) to connect to -l, --log-level string Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info") --tls Use TLS; implied by --tlsverify --tlscacert string Trust certs signed only by this CA (default "/home/ben/.docker/ca.pem") --tlscert string Path to TLS certificate file (default "/home/ben/.docker/cert.pem") --tlskey string Path to TLS key file (default "/home/ben/.docker/key.pem") --tlsverify Use TLS and verify the remote -v, --version Print version information and quitManagement Commands: builder Manage builds config Manage Docker configs container Manage containers context Manage contexts engine Manage the docker engine image Manage images network Manage networks node Manage Swarm nodes plugin Manage plugins secret Manage Docker secrets service Manage services stack Manage Docker stacks swarm Manage Swarm system Manage Docker trust Manage trust on Docker images volume Manage volumesCommands: attach Attach local standard input, output, and error streams to a running container build Build an image from a Dockerfile commit Create a new image from a container's changes cp Copy files/folders between a container and the local filesystem create Create a new container diff Inspect changes to files or directories on a container's filesystem events Get real time events from the server exec Run a command in a running container export Export a container's filesystem as a tar archive history Show the history of an image images List images import Import the contents from a tarball to create a filesystem image info Display system-wide information inspect Return low-level information on Docker objects kill Kill one or more running containers load Load an image from a tar archive or STDIN login Log in to a Docker registry logout Log out from a Docker registry logs Fetch the logs of a container pause Pause all processes within one or more containers port List port mappings or a specific mapping for the container ps List containers pull Pull an image or a repository from a registry push Push an image or a repository to a registry rename Rename a container restart Restart one or more containers rm Remove one or more containers rmi Remove one or more images run Run a command in a new container save Save one or more images to a tar archive (streamed to STDOUT by default) search Search the Docker Hub for images start Start one or more stopped containers stats Display a live stream of container(s) resource usage statistics stop Stop one or more running containers tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE top Display the running processes of a container unpause Unpause all processes within one or more containers update Update configuration of one or more containers version Show the Docker version information wait Block until one or more containers stop, then print their exit codesRun 'docker COMMAND --help' for more information on a command.The assumption was that there should be a kind of compare command. How could one compare a local image with one in a private registry? For example, if nginx:1.17.5 has been pulled locally and resides in a private docker registry then a command should indicated that:
docker compare nginx:1.17.5 quay.io/some-org/nginx:1.17.5the command should return:
exit 1, the docker image already resides in the docker private registry