Using this user script, you can replace any textarea you encounter on gist.github.com with a Bespin editor – making editing much more pleasant.

gistBespin.user.js

// ==UserScript==
// @name         Bespin For Gist.Github
// @namespace    gistBespin
// @include      http://www.ngv.vic.gov.au/*
// @include      https://www.ngv.vic.gov.au/*
// @datecreated  2010-07-03
// @lastupdated  2010-07-03
// @version      0.1
// @author       Erik Vergobbi Vold
// @license      MPL 1.1/GPL 2.0/LGPL 2.1
// @description  Using this user script, you can replace any textarea you encounter on gist.github.com with a Bespin editor – making editing much more pleasant.
// ==/UserScript==

// code below taken from https://bespin.mozillalabs.com/bookmarklet/
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Bespin.
 *
 * The Initial Developer of the Original Code is
 * Mozilla.
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Bespin Team ([email protected])
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

var execute = function() {
    /** --------------------------------------------------------------------
     * Load Bespin only when it's not already on the page.
     */
    if (typeof bespin == 'undefined') {
        /** Adjust the following variables as needed **/
        var base = 'https://bespin.mozillalabs.com/bookmarklet/';
        var proxyFile = 'proxy.html';
        var bespinBase = base + "bespin/";

        var head = document.getElementsByTagName('head')[0];
        var iFrame;

        /** Add the bespin_base link to the header **/
        var l =  document.createElement('link');
        l.setAttribute('id', 'bespin_base');
        l.setAttribute('href', bespinBase);
        head.appendChild(l);

        /** Add some basic Bespin CSS **/
        l =  document.createElement('style');
        l.innerHTML = '.bespin{border:1px solid gray;}';
        head.appendChild(l);

        /** --------------------------------------------------------------------
         * BEGIN: Proxy handling code.
         */
        var postProxyMsg = function(obj) {
            iFrame.contentWindow.postMessage(JSON.stringify(obj), '*');
        };

        /** --------------------------------------------------------------------
         * Worker proxy implementation.
         */
        var lastWorker = 0;
        var workerList = [];

        /** Fake Worker class **/
        var WorkerProxy = function(url) {
            this.id = lastWorker ++;
            postProxyMsg({
                id: this.id,
                task: 'newWorker',
                url: url
            });
            workerList[this.id] = this;
        };

        WorkerProxy.prototype.postMessage = function(msg) {
            postProxyMsg({
                id: this.id,
                task: 'postWorker',
                msg: msg
            });
        };

        WorkerProxy.prototype.terminate = function() {
            postProxyMsg({
                id: this.id,
                task: 'terminateWorker'
            });
            delete workerList[this.id];
        };

        /** --------------------------------------------------------------------
         * XHR proxy implementation.
         */
        var xhrList = [];
        var lastXhr = 0;
        var XhrProxy = function(method, url, async, beforeSendCallback, pr) {
            postProxyMsg({
                id: lastXhr,
                task: 'xhr',
                method: method,
                url: url
            });

            xhrList[lastXhr] = pr;
            lastXhr ++;
        };

        /** --------------------------------------------------------------------
         * Handler for messages from the proxy.
         */
        var messageHandler = function(e){
            var obj = JSON.parse(e.data);

            switch (obj.type) {
                case 'xhr':
                    var pr = xhrList[obj.id];
                    if (obj.success) {
                        pr.resolve(obj.data);
                    } else {
                        pr.reject(new Error(obj.data));
                    }

                    delete xhrList[obj.id];

                    break;

                case 'worker':
                    var worker = workerList[obj.id];
                    if (obj.success) {
                        worker.onmessage.call(worker, {
                            data: obj.msg
                        });
                    } else {
                        worker.onerror.call(worker, JSON.parse(obj.msg));
                    }

                    break;
            }

        };
        window.addEventListener('message', messageHandler, false);

        /** --------------------------------------------------------------------
         * Put the xhr and worker proxy on the Bespin object.
         */
        bespin = {
            proxy: {
                xhr: XhrProxy,
                worker: WorkerProxy
            }
        };

        /** --------------------------------------------------------------------
         * Create an iFrame that has the proxy file as source. After the proxy
         * file is loaded, add a script tag with the BespinEmbedded.js file
         * as source to the current page. This will start the Bespin boot process.
         */
        iFrame = l =  document.createElement('iFrame');
        l.setAttribute('src', base + proxyFile);
        l.onload = function() {
            s = document.createElement('script');
            s.src = bespinBase + 'BespinEmbedded.js';
            head.appendChild(s);

            /** Called when Bespin has finished loading. **/
            window.onBespinLoad = function() {
                var $ = bespin.tiki.require("jquery").$;
                var currentTextArea = null;
                var bespinButton = document.createElement("img");
                bespinButton.setAttribute('style', 'display:none; position:absolute');
                bespinButton.setAttribute('src', base + 'bespin-logo.png');
                document.body.appendChild(bespinButton);
                
                $(bespinButton).click(function(evt) {
                    if (currentTextArea) {
                        $(bespinButton).hide();
                        bespin.useBespin(currentTextArea, {
                            stealFocus: true
                        });
                    }
                });
                
                $('textarea').mouseenter(function(evt) {
                    currentTextArea = evt.target;
                    var pos = $(evt.target).offset();
                    var width = $(evt.target).width();
                    $(bespinButton).css({top: pos.top + 'px', 
                                         left: pos.left + width + 'px'}).show();
                });
            };
        };
        head.appendChild(l);
    }
};

var script = document.createElement("script");
script.textContent = "(" + execute.toString() + ")();"
document.body.appendChild(script);