location: back override option

Added tests for res.location('back')
Made option to turn off built 'back' referrer functionality when not
working the way it was expected.

fixes: #3290

lib/application.js

@@ -72,6 +72,7 @@ app.defaultConfiguration = function defaultConfiguration() {
 
   // default settings
   this.enable('x-powered-by');
+  this.enable('location back-referrer');
   this.set('etag', 'weak');
   this.set('env', env);
   this.set('query parser', 'extended');

lib/response.js

@@ -834,7 +834,7 @@ res.location = function location(url) {
   var loc = url;
 
   // "back" is an alias for the referrer
-  if (url === 'back') {
+  if (url === 'back' && this.app.enabled('location back-referrer')) {
     loc = this.req.get('Referrer') || '/';
   }
 

test/res.location.js

@@ -99,6 +99,21 @@ describe('res', function(){
         .expect('Location', '/')
         .expect(200, done)
       })
+
+      it('should set the header to "back" on back', function (done) {
+        var app = express()
+
+        app.disable("location back-referrer")
+
+        app.use(function (req, res) {
+          res.location('back').end()
+        })
+
+        request(app)
+        .get('/')
+        .expect('Location', 'back')
+        .expect(200, done)
+      })
     })
   })
 })