$ go get github.com/containers/oci-fetch/oci-fetch
$ oci-fetch --help
oci-fetch will fetch an OCI image and store it on the local filesystem in a
.tar.gz file

Usage:
  oci-fetch docker://HOST/IMAGENAME[:TAG] FILEPATH [flags]

Examples:
oci-fetch docker://registry-1.docker.io/library/nginx:latest nginx.oci

Flags:
      --debug                            print out debugging information to stderr
  -h, --help                             help for oci-fetch
      --insecure-allow-http              don't enforce encryption when fetching images
      --insecure-skip-tls-verification   don't perform TLS certificate verification