Updated cache buster logic

Removed css and script busters in favour of a uuid/guid cache
buster that is generated when the app starts.

This change means that in the event your NodeBB crashes often,
users will not be able to rely on their browser cache to serve
an unchanged style/js file, but if that's the case, you've
got bigger problems anyway.

re: #3573

src/controllers/api.js

@@ -70,8 +70,6 @@ apiController.getConfig = function(req, res, next) {
 	config.environment = process.env.NODE_ENV;
 	config.loggedIn = !!req.user;
 	config['cache-buster'] = meta.config['cache-buster'] || '';
-	config['script-buster'] = meta.js.hash || '';
-	config['css-buster'] = meta.css.hash || '';
 	config.requireEmailConfirmation = parseInt(meta.config.requireEmailConfirmation, 10) === 1;
 	config.topicPostSort = meta.config.topicPostSort || 'oldest_to_newest';
 	config.categoryTopicSort = meta.config.categoryTopicSort || 'newest_to_oldest';

src/meta/configs.js

@@ -4,7 +4,8 @@
 var winston = require('winston'),
 	db = require('../database'),
 	pubsub = require('../pubsub'),
-	nconf = require('nconf');
+	nconf = require('nconf'),
+	utils = require('../../public/src/utils');
 
 module.exports = function(Meta) {
 
@@ -20,6 +21,8 @@ module.exports = function(Meta) {
 				return callback(err);
 			}
 
+			config['cache-buster'] = utils.generateUUID();
+
 			Meta.config = config;
 			callback();
 		});

src/webserver.js

@@ -117,24 +117,6 @@ function cacheStaticFiles(callback) {
 
 	app.enable('cache');
 	app.enable('minification');
-
-	// Configure cache-buster timestamp
-	require('child_process').exec('git describe --tags', {
-		cwd: path.join(__dirname, '../')
-	}, function(err, stdOut) {
-		if (!err) {
-			meta.config['cache-buster'] = stdOut.trim();
-			callback();
-		} else {
-			fs.stat(path.join(__dirname, '../package.json'), function(err, stats) {
-				if (err) {
-					return callback(err);
-				}
-				meta.config['cache-buster'] = new Date(stats.mtime).getTime();
-				callback();
-			});
-		}
-	});
 }
 
 function listen(callback) {