anchor.diff:      created ? "1970-01-01T00:00:01Z",
       # Optional bash script to run on the files prior to fixturizing the layer.
       extraCommands ? "",
  +    # Optional bash script to run inside fakeroot environment.
  +    # Could be used for changing ownership of files in customisation layer.
  +    fakeRootCommands ? "",
       # We pick 100 to ensure there is plenty of room for extension. I
       # believe the actual maximum is 128.
       maxLayers ? 100
  
positive.code:         name = "${baseName}-customisation-layer";
          paths = contentsList;
          inherit extraCommands;
          postBuild = ''
            mv $out old_out
            (cd old_out; eval "$extraCommands" )
  
            mkdir $out
  
            tar \
              --sort name \
              --owner 0 --group 0 --mtime "@$SOURCE_DATE_EPOCH" \
              --hard-dereference \
              -C old_out \
              -cf $out/layer.tar .
  
            sha256sum $out/layer.tar \
              | cut -f 1 -d ' ' \
  
negative.code:   coreutils,
    docker,
    e2fsprogs,
    fakeroot,
    findutils,
    go,
    jq,
  