Added changeOrigin option with test and docs

lib/http-proxy.js

@@ -40,6 +40,7 @@ module.exports.createProxyServer =
    *    toProxy: <true/false, explicitly specify if we are proxying to another proxy>
    *    prependPath: <true/false, Default: true - specify whether you want to prepend the target's path to the proxy path>
    *    localAddress : <Local interface string to bind for outgoing connections>
+   *    changeOrigin: true/false, Default: false - changes the origin of the host header to the target URL>
    *  }
    *
    *  NOTE: `options.ws` and `options.ssl` are optional.

lib/http-proxy/common.js

@@ -74,6 +74,10 @@ common.setupOutgoing = function(outgoing, options, req, forward) {
 
   outgoing.path = common.urlJoin(targetPath, outgoingPath);
 
+  if (options.changeOrigin) {
+    outgoing.headers.host = outgoing.host;
+  }
+  
   return outgoing;
 };
 

test/lib-http-proxy-passes-web-incoming-test.js

@@ -264,4 +264,30 @@ describe('#createProxyServer.web() using own http server', function () {
     source.listen('8080');
     http.request('http://127.0.0.1:8086', function() {}).end();
   });
+
+  it('should proxy the request and handle changeOrigin option', function (done) {
+    var proxy = httpProxy.createProxyServer({
+      target: 'http://127.0.0.1:8080',
+      changeOrigin: true
+    });
+
+    function requestHandler(req, res) {
+      proxy.web(req, res);
+    }
+
+    var proxyServer = http.createServer(requestHandler);
+
+    var source = http.createServer(function(req, res) {
+      source.close();
+      proxyServer.close();
+      expect(req.method).to.eql('GET');
+      expect(req.headers.host.split(':')[1]).to.eql('8080');
+      done();
+    });
+
+    proxyServer.listen('8081');
+    source.listen('8080');
+
+    http.request('http://127.0.0.1:8081', function() {}).end();
+  });
 });