creating a local.example.js as a sample file to extend configuration to local repository without committing these changes and also replacing .extend() with .merge() for local repository changes

config/config.js

@@ -7,14 +7,26 @@ var _ = require('lodash'),
 	glob = require('glob'),
 	fs = require('fs');
 
+/**
+ * Resolve environment configuration by extending each env configuration file,
+ * and lastly merge/override that with any local repository configuration that exists
+ * in local.js
+ */
+var resolvingConfig = function() {
+	var conf = {};
+
+	conf = _.extend(
+		require('./env/all'),
+		require('./env/' + process.env.NODE_ENV) || {}
+	);
+
+	return _.merge(conf, (fs.existsSync('./config/env/local.js') && require('./env/local.js')) || {});
+};
+
 /**
  * Load app configurations
  */
-module.exports = _.extend(
-	require('./env/all'),
-	require('./env/' + process.env.NODE_ENV),
-	(fs.existsSync('./config/env/local.js') && require('./env/local.js')) || {}
-);
+module.exports = resolvingConfig();
 
 /**
  * Get files by glob patterns

config/env/local.example.js

@@ -0,0 +1,23 @@
+'use strict';
+
+// Rename this file to local.js for having a local configuration variables that
+// will not get commited and pushed to remote repositories.
+// Use it for your API keys, passwords, etc.
+
+/* For example:
+
+module.exports = {
+	db: {
+		uri: 'mongodb://localhost/local-dev',
+		options: {
+			user: '',
+			pass: ''
+		}
+	},
+	facebook: {
+		clientID: process.env.FACEBOOK_ID || 'APP_ID',
+		clientSecret: process.env.FACEBOOK_SECRET || 'APP_SECRET',
+		callbackURL: '/auth/facebook/callback'
+	}
+};
+*/

gruntfile.js

@@ -148,7 +148,7 @@ module.exports = function(grunt) {
 		},
 		copy: {
 		    localConfig: {
-	            src: 'config/env/development.js',
+	            src: 'config/env/local.example.js',
 	            dest: 'config/env/local.js',
 	            filter: function() {
 	            	return !fs.existsSync('config/env/local.js');