retry: redirect back to page user came from to preserve query params.…

… for #524

app.py

@@ -525,7 +525,8 @@ def post(self):
       self.abort(400, 'Unexpected key kind %s', entity.key.kind())
 
     self.messages.add('Retrying. Refresh in a minute to see the results!')
-    self.redirect(entity.source.get().bridgy_url(self))
+    self.redirect(self.request.get('redirect_to').encode('utf-8') or
+                  entity.source.get().bridgy_url(self))
 
 
 class RedirectToFrontPageHandler(util.Handler):

templates/social_user.html

@@ -204,6 +204,7 @@
 
     <form method="post" action="/retry">
       <input name="key" type="hidden" value="{{ response.key.urlsafe }}" />
+      <input name="redirect_to" type="hidden" value="{{ request.url }}" />
       <button id="retry-button" type="submit" class="btn btn-default">
         Retry</button>
     </form>

test/test_app.py

@@ -84,6 +84,14 @@ def test_retry(self):
     # webmention endpoints for URL domains should be refreshed
     self.assertIsNone(memcache.get('W https skipped'))
 
+  def test_retry_redirect_to(self):
+    key = self.responses[0].put()
+    response = app.application.get_response(
+      '/retry', method='POST', body='key=%s&redirect_to=/foo/bar' % key.urlsafe())
+    self.assertEquals(302, response.status_int)
+    self.assertEquals('http://localhost/foo/bar',
+                      response.headers['Location'].split('#')[0])
+
   def test_poll_now_and_retry_response_missing_key(self):
     for endpoint in '/poll-now', '/retry':
       for body in '', 'key=' + self.responses[0].key.urlsafe():  # hasn't been stored