code: protected Content getNavLinkHelp() {
          String helpfile = configuration.helpfile;
          DocPath helpfilenm;
          if (helpfile.isEmpty()) {
              helpfilenm = DocPaths.HELP_DOC;
          } else {
              DocFile file = DocFile.createFileForInput(configuration, helpfile);
              helpfilenm = DocPath.create(file.getName());
          }
          Content linkContent = getHyperLink(pathToRoot.resolve(helpfilenm),
                  helpLabel, "", "");
          Content li = HtmlTree.LI(linkContent);
          return li;
      }
docs: Get help file link. If user has provided a help file, then generate a
  link to the user given file, which is already copied to current or
  destination directory.
  
  @return a content tree for the link