anchor.diff:    # dockerTools chain.
     onTopOfPulledImage = buildImage {
       name = "onTopOfPulledImage";
  +    tag = "latest";
       fromImage = nixFromDockerHub;
       contents = [ pkgs.hello ];
     };
  
positive.code:   # docker run -it --rm nix nix-store -qR $(nix-build '<nixpkgs>' -A nix)
    nix = buildImageWithNixDb {
      name = "nix";
      contents = [
        # nix-store uses cat program to display results as specified by
        # the image env variable NIX_PAGER.
  
negative.code:   in
    buildImage {
      name = "nginx-container";
      tag = "latest";
      contents = pkgs.nginx;
  
      runAsRoot = ''
  