Ensure `response.Request` is populated for responses from cache

https://github.com/github/hub/runs/397657829

github/http.go

@@ -343,6 +343,7 @@ func (c *simpleClient) cacheRead(key string, req *http.Request) (res *http.Respo
 		res = &http.Response{
 			Body:    ioutil.NopCloser(bytes.NewBufferString(parts[1])),
 			Header:  http.Header{},
+			Request: req,
 		}
 		headerLines := strings.Split(parts[0], "\r\n")
 		if len(headerLines) < 1 {