fix Mocha#grep(), escape regexp strings

bin/_mocha

@@ -218,7 +218,7 @@ mocha.suite.bail(program.bail);
 
 // --grep
 
-if (program.grep) mocha.grep(new RegExp(utils.escapeRegexp(program.grep)));
+if (program.grep) mocha.grep(new RegExp(program.grep));
 
 // --invert
 

lib/mocha.js

@@ -8,7 +8,8 @@
  * Module dependencies.
  */
 
-var path = require('path');
+var path = require('path')
+  , utils = require('./utils');
 
 /**
  * Expose `Mocha`.
@@ -20,7 +21,7 @@ exports = module.exports = Mocha;
  * Expose internals.
  */
 
-exports.utils = require('./utils');
+exports.utils = utils;
 exports.interfaces = require('./interfaces');
 exports.reporters = require('./reporters');
 exports.Runnable = require('./runnable');
@@ -154,16 +155,16 @@ Mocha.prototype._growl = function(runner, reporter) {
 };
 
 /**
- * Add regexp to grep for to the options object
+ * Add regexp to grep, if `re` is a string it is escaped.
  *
- * @param {RegExp} or {String} re
+ * @param {RegExp|String} re
  * @return {Mocha}
  * @api public
  */
 
 Mocha.prototype.grep = function(re){
   this.options.grep = 'string' == typeof re
-    ? new RegExp(re)
+    ? new RegExp(utils.escapeRegexp(re))
     : re;
   return this;
 };