anchor.diff:  %%  out_dir: where to put preprocessed css files
   %%           "priv/www/stylesheets" by default
   %%
  +%%  stylesheets: stylus files to compile
  +%%           [] by default
  +%%
   %% The default settings are the equivalent of:
   %%   {js_stylus, [
  -%%               {stylus,   "/usr/local/bin/stylus"},
  -%%               {doc_root, "priv/assets/stylesheets"},
  -%%               {out_dir,  "priv/www/stylesheets"}
  +%%               {stylus,       "/usr/local/bin/stylus"},
  +%%               {doc_root,     "priv/assets/stylesheets"},
  +%%               {out_dir,      "priv/www/stylesheets"}
  +%%               {stylesheets,  []}
   %%              ]}.
   %%
   
  
positive.code: %% Public API
  %% ===================================================================
  
  compile(Config, _AppFile) ->
      Options = options(Config),
      OutDir = option(out_dir, Options),
      DocRoot = option(doc_root, Options),
      Stylus = option(stylus_path, Options),
      case stylus_is_present(Stylus) of
          true ->
              Cmd = lists:flatten([Stylus, " -o ", OutDir, " ", DocRoot]),
              ShOpts = [{use_stdout, false}, return_on_error],
              case rebar_utils:sh(Cmd, ShOpts) of
                  {ok, _} ->
  
negative.code:                     rebar_log:log(error, "Stylus asset processing failed failed:~n  ~p~n",
                             [Reason]),
                      rebar_utils:abort()
              end,
              ok;
          false ->
              rebar_log:log(error,
                  "Bypassing stylesheet processing of ~s: stylus missing.~n", [DocRoot]),
  