code: @GwtIncompatible("Unnecessary")
    private String expandCommandLinePath(String path, JSModule forModule) {
      String sub;
      if (forModule != null) {
        sub = config.moduleOutputPathPrefix + forModule.getName() + ".js";
      } else if (!config.module.isEmpty()) {
        sub = config.moduleOutputPathPrefix;
      } else {
        sub = config.jsOutputFile;
      }
      return path.replace("%outname%", sub);
    }
docs: Expand a file path specified on the command-line.
  
  <p>Most file paths on the command-line allow an %outname% placeholder. The placeholder will
  expand to a different value depending on the current output mode. There are three scenarios:
  
  <p>1) Single JS output, single extra output: sub in jsOutputPath. 2) Multiple JS output, single
  extra output: sub in the base module name. 3) Multiple JS output, multiple extra output: sub in
  the module output file.
  
  <p>Passing a JSModule to this function automatically triggers case #3. Otherwise, we'll use
  strategy #1 or #2 based on the current output mode.