anchor.diff:        mkdir "$unpackDir"
         cd "$unpackDir"
   
  -      renamed="$TMPDIR/${basename}"
  +      renamed="$TMPDIR/${tmpFilename}"
         mv "$downloadedFile" "$renamed"
         unpackFile "$renamed"
       ''
  
positive.code: , urls ? []
  , extraPostFetch ? ""
  , name ? "source"
  , ... } @ args:
  
  (fetchurl (let
    basename = baseNameOf (if url != "" then url else builtins.head urls);
  in {
    inherit name;
  
  
negative.code:     + ''
        chmod 755 "$out"
      '';
  } // removeAttrs args [ "stripRoot" "extraPostFetch" "extension" ])).overrideAttrs (x: {
    # Hackety-hack: we actually need unzip hooks, too
    nativeBuildInputs = x.nativeBuildInputs ++ [ unzip ];
  })
  