gist_link_user_js.user.js

// ==UserScript==
// @name           gist.user.js
// @namespace      http://github.com/hotchpotch
// @description    install greasemonkey (user.js)
// @include        http://gist.github.com/*
// @include        https://gist.github.com/*
// ==/UserScript==

(function() {
  $X('id("files")//div[@class="info"]/span').forEach(function(e) {
     var filename = e.innerHTML;
     if (/\.user\.js$/.test(filename)) {
       var link = $X('parent::div/following-sibling::div[@class="actions"]/a', e)[0];
       if (link) {
         var el = link.cloneNode(true);
         el.href += '?' + filename;
         el.innerHTML = filename;
         e.parentNode.replaceChild(el,e);
       }
     }
  });
  function $X (exp, context) {
      context = context || document;
      var resolver = function (prefix) {
          var o = document.createNSResolver(context)(prefix);
          return o ? o : (document.contentType == "text/html") ? "" : "http://www.w3.org/1999/xhtml";
      }
      var exp = document.createExpression(exp, resolver);
      var result = exp.evaluate(context, XPathResult.ANY_TYPE, null);
      switch (result.resultType) {
          case XPathResult.STRING_TYPE : return result.stringValue;
          case XPathResult.NUMBER_TYPE : return result.numberValue;
          case XPathResult.BOOLEAN_TYPE: return result.booleanValue;
          case XPathResult.UNORDERED_NODE_ITERATOR_TYPE: {
              // not ensure the order.
              var ret = [];
              var i = null;
              while (i = result.iterateNext()) {
                  ret.push(i);
              }
              return ret;
          }
      }
      return null;
  };
})();

great!