Allow passing of explicit options to Model.update()

lib/Model.js

@@ -534,17 +534,36 @@ Model.prototype.insert = Model.prototype.create = function (object, options, cal
     }, this), prepComplete);
 };
 
-Model.prototype.update = function (conditions, changes, callback) {
+Model.prototype.update = function (conditions, changes, options, callback) {
     /// <signature>
     /// <summary>Updates all documents in the collection which match the specified conditions - making the requested changes</summary>
     /// <param name="conditions" type="Object">The conditions used to select objects to be updated</param>
     /// <param name="changes" type="Object">The changes to be made to objects in the collection</param>
     /// <param name="callback" optional="true" value="(function(err, count) { })">A function to be called once the update has completed</param>
     /// </signature>
+    /// <signature>
+    /// <summary>Updates all documents in the collection which match the specified conditions - making the requested changes</summary>
+    /// <param name="conditions" type="Object">The conditions used to select objects to be updated</param>
+    /// <param name="changes" type="Object">The changes to be made to objects in the collection</param>
+    /// <param name="options" type="Object">The options to be passed to the update method</param>
+    /// <param name="callback" value="(function(err, count) { })">A function to be called once the update has completed</param>
+    /// </signature>
 
+    options = options || {};
+
+    if(typeof options == 'function') {
+        callback = options;
+        options = {};
+    }
+
+    _.defaults(options, {
+        w: callback ? 1 : 0, 
+        multi: true
+    });
+
     this.toSource(conditions);
 
-    this.collection.update(conditions, changes, { w: callback ? 1 : 0, multi: true }, (function(err, modified) {
+    this.collection.update(conditions, changes, options, (function(err, modified) {
         if (err) this.emit('error', err);
         return callback(err, modified);
     }).bind(this));