HttpRequest.AddHeader() also affects on redirected requests when Http…

…Request.KeepTemporaryHeadersOnRedirect = true.

Update README.md:
Added new property HttpRequest.KeepTemporaryHeadersOnRedirect (default true).

Leaf.xNet.Tests/~Http/HttpRequestTests.cs

@@ -162,6 +162,39 @@ public void FilterCookieDomains()
         }
 
         /*
+        [TestMethod]
+        public void KeepTempHeadersAfterRedirect()
+        {
+            using (var req = new HttpRequest())
+            {
+                req.Proxy = HttpProxyClient.Parse("127.0.0.1:8887");
+                req.Proxy.AbsoluteUriInStartingLine = false;
+
+                req.KeepTemporaryHeadersOnRedirect = true;
+                req.AddHeader(HttpHeader.Referer, "https://google.com");
+                var res = req.Get("http://google.com");
+
+                var res3 = req.Get("http://ya.ru");
+
+                req.KeepTemporaryHeadersOnRedirect = false;
+                req.AddHeader(HttpHeader.Referer, "https://google.com");
+                var resNo = req.Get("http://google.com");
+
+
+
+                req.KeepTemporaryHeadersOnRedirect = true;
+                req.AddHeader(HttpHeader.Referer, "https://google.com");
+                req.Get("http://google.com").None();
+
+                req.KeepTemporaryHeadersOnRedirect = false;
+                req.AddHeader(HttpHeader.Referer, "https://google.com");
+                req.Get("http://google.com").None();
+
+
+            }
+        }
+
+        
         [TestMethod]
         public void AvoidCrossdomainCookieDuplication()
         {

Leaf.xNet/~Http/HttpRequest.cs

@@ -261,6 +261,11 @@ public event EventHandler<DownloadProgressChangedEventArgs> DownloadProgressChan
         /// </summary>
         public bool AllowEmptyHeaderValues { get; set; }
 
+        /// <summary>
+        /// Следует ли отправлять временные заголовки (добавленные через <see cref="AddHeader(string,string)"/>) переадресованным запросам.
+        /// По умолчанию <see langword="true"/>.
+        /// </summary>
+        public bool KeepTemporaryHeadersOnRedirect { get; set; } = true;
 
         /// <summary>
         /// Включить отслеживание заголовков в промежуточных запросах (переадресованные) и сохранять их в <see cref="HttpResponse.MiddleHeaders"/>.
@@ -1327,7 +1332,7 @@ public HttpResponse Raw(HttpMethod method, Uri address, HttpContent content = nu
             {
                 content?.Dispose();
 
-                ClearRequestData();
+                ClearRequestData(false);
             }
         }
 
@@ -1670,7 +1675,8 @@ private HttpResponse Request(HttpMethod method, Uri address, HttpContent content
                     if (Response.HasExternalRedirect)
                         return Response;
 
-                    ClearRequestData();
+                    ClearRequestData(true);
+
                     method = HttpMethod.GET;
                     address = Response.RedirectAddress;
                     content = null;
@@ -2207,12 +2213,14 @@ private void ReportBytesReceived(int bytesReceived)
             }
         }
 
-        private void ClearRequestData()
+        private void ClearRequestData(bool redirect)
         {
             _content = null;
 
             _temporaryMultipartContent = null;
-            _temporaryHeaders = null;
+
+            if (!redirect || !KeepTemporaryHeadersOnRedirect)
+                _temporaryHeaders = null;
         }
 
         private HttpException NewHttpException(string message,

README.md

@@ -37,6 +37,15 @@ var resp = httpRequest.Get("https://...");
 bool isCloudFlared = resp.isCloudFlared();
 ```
 
+### Keep temporary headers (when redirected)
+It's enabled by default. But you can disable this behavior:
+```csharp
+httpRequest.KeepTemporaryHeadersOnRedirect = false;
+httpRequest.AddHeader(HttpHeader.Referer, "https://google.com");
+httpRequest.Get("http://google.com").None();
+// After redirection to www.google.com - request won't have Referer header because KeepTemporaryHeadersOnRedirect = false
+```
+
 ### Middle response headers (when redirected)
 ```csharp
 httpRequest.EnableMiddleHeaders = true;