anchor.diff:  , name ? "source"
   , ... } @ args:
   
  -lib.overrideDerivation (fetchurl ({
  +(fetchurl ({
     inherit name;
   
     recursiveHash = true;
  
positive.code:       mv "$unpackDir" "$out"
      '') #*/
      + extraPostFetch;
  } // removeAttrs args [ "stripRoot" "extraPostFetch" ]))
  # Hackety-hack: we actually need unzip hooks, too
  (x: {nativeBuildInputs = x.nativeBuildInputs++ [unzip];})
  
negative.code: 
    postFetch =
      ''
        unpackDir="$TMPDIR/unpack"
        mkdir "$unpackDir"
        cd "$unpackDir"
  