Provide Handlebars.noConflict implementation

Allows for users who are loading via a global pattern to avoid conflicting with other instances of the library.

Fixes #887

lib/handlebars.js

@@ -30,6 +30,15 @@ var create = function() {
 Handlebars = create();
 Handlebars.create = create;
 
+/*jshint -W040 */
+var root = typeof global !== 'undefined' ? global : window,
+    $Handlebars = root.Handlebars;
+Handlebars.noConflict = function() {
+  if (root.Handlebars === Handlebars) {
+    root.Handlebars = $Handlebars;
+  }
+};
+
 Handlebars['default'] = Handlebars;
 
 export default Handlebars;

lib/handlebars.runtime.js

@@ -29,6 +29,15 @@ var create = function() {
 var Handlebars = create();
 Handlebars.create = create;
 
+/*jshint -W040 */
+var root = typeof global !== 'undefined' ? global : window,
+    $Handlebars = root.Handlebars;
+Handlebars.noConflict = function() {
+  if (root.Handlebars === Handlebars) {
+    root.Handlebars = $Handlebars;
+  }
+};
+
 Handlebars['default'] = Handlebars;
 
 export default Handlebars;

spec/env/browser.js

@@ -5,7 +5,7 @@ var _ = require('underscore'),
     fs = require('fs'),
     vm = require('vm');
 
-global.Handlebars = undefined;
+global.Handlebars = 'no-conflict';
 vm.runInThisContext(fs.readFileSync(__dirname + '/../../dist/handlebars.js'), 'dist/handlebars.js');
 
 global.CompilerContext = {

spec/env/runtime.js

@@ -5,7 +5,7 @@ var _ = require('underscore'),
     fs = require('fs'),
     vm = require('vm');
 
-global.Handlebars = undefined;
+global.Handlebars = 'no-conflict';
 vm.runInThisContext(fs.readFileSync(__dirname + '/../../dist/handlebars.runtime.js'), 'dist/handlebars.runtime.js');
 
 var parse = require('../../dist/cjs/handlebars/compiler/base').parse;
@@ -13,6 +13,8 @@ var compiler = require('../../dist/cjs/handlebars/compiler/compiler');
 var JavaScriptCompiler = require('../../dist/cjs/handlebars/compiler/javascript-compiler')['default'];
 
 global.CompilerContext = {
+  browser: true,
+
   compile: function(template, options) {
     // Hack the compiler on to the environment for these specific tests
     handlebarsEnv.precompile = function(template, options) {

spec/runtime.js

@@ -60,4 +60,22 @@ describe('runtime', function() {
       equal(template._child(1, undefined, [{bar: 'baz'}])(), 'baz');
     });
   });
+
+  describe('#noConflict', function() {
+    if (!CompilerContext.browser) {
+      return;
+    }
+
+    it('should reset on no conflict', function() {
+      var reset = Handlebars;
+      Handlebars.noConflict();
+      equal(Handlebars, 'no-conflict');
+
+      Handlebars = 'really, none';
+      reset.noConflict();
+      equal(Handlebars, 'really, none');
+
+      Handlebars = reset;
+    });
+  });
 });