When redirecting with a relative Location, add the port number to the new URL

Author: spevans

Foundation/URLSession/http/HTTPURLProtocol.swift

@@ -391,17 +391,20 @@ internal extension _HTTPURLProtocol {
 
         // If targetURL has only relative path of url, create a new valid url with relative path
         // Otherwise, return request with targetURL ie.url from location field
-        guard targetURL.scheme == nil || targetURL.host == nil else {
+        guard targetURL.scheme == nil || targetURL.host == nil || targetURL.port == nil else {
             request.url = targetURL
             return request
         }
 
         let scheme = request.url?.scheme
         let host = request.url?.host
+        let port = request.url?.port
 
         var components = URLComponents()
         components.scheme = scheme
         components.host = host
+        components.port = port
+
         //The path must either begin with "/" or be an empty string.
         if targetURL.relativeString.first != "/" {
             components.path = "/" + targetURL.relativeString