Added comment

Author: Nyholm

lib/Github/HttpClient/Cache/ResponseSerializer.php

@@ -28,6 +28,10 @@ public static function serialize(ResponseInterface $response, StreamFactory $str
         if ($bodyStream->isSeekable()) {
             $bodyStream->rewind();
         } else {
+            /*
+             * If the body is not seekbable we can not rewind it. The stream could be a type of stream
+             * that you only can read once. That is why we have to replace the old stream with a new one.
+             */
             $response = $response->withBody($streamFactory->createStream($body));
         }