rebaseline_server: constrain setADir/setBDir to consistently refer to single directories, not lists

gm/rebaseline_server/server.py

 #!/usr/bin/python
 
 """
 Copyright 2013 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 
 HTTP server for our HTML rebaseline viewer.
 """
@@ skipping 579 matching lines @@
     """ Handle a GET request for live-generated image diff data.
 
     Args:
       url_remainder: string indicating which image diffs to generate
       prefetch_only: if True, the user isn't waiting around for results
     """
     param_dict = urlparse.parse_qs(url_remainder)
     download_all_images = (
         param_dict.get(LIVE_PARAM__DOWNLOAD_ONLY_DIFFERING, [''])[0].lower()
         not in ['1', 'true'])
-    setA_dirs = param_dict[LIVE_PARAM__SET_A_DIR]
-    setB_dirs = param_dict[LIVE_PARAM__SET_B_DIR]
+    setA_dir = param_dict[LIVE_PARAM__SET_A_DIR][0]
+    setB_dir = param_dict[LIVE_PARAM__SET_B_DIR][0]
     setA_section = self._validate_summary_section(
         param_dict.get(LIVE_PARAM__SET_A_SECTION, [None])[0])
     setB_section = self._validate_summary_section(
         param_dict.get(LIVE_PARAM__SET_B_SECTION, [None])[0])
 
     # If the sets show expectations vs actuals, always show expectations on
     # the left (setA).
     if ((setA_section == gm_json.JSONKEY_ACTUALRESULTS) and
         (setB_section == gm_json.JSONKEY_EXPECTEDRESULTS)):
-      setA_dirs, setB_dirs = setB_dirs, setA_dirs
+      setA_dir, setB_dir = setB_dir, setA_dir
       setA_section, setB_section = setB_section, setA_section
 
     # Are we comparing some actuals against expectations stored in the repo?
     # If so, we can allow the user to submit new baselines.
     is_editable = (
         (setA_section == gm_json.JSONKEY_EXPECTEDRESULTS) and
-        (setA_dirs[0].startswith(compare_rendered_pictures.REPO_URL_PREFIX)) and
+        (setA_dir.startswith(compare_rendered_pictures.REPO_URL_PREFIX)) and
         (setB_section == gm_json.JSONKEY_ACTUALRESULTS))
 
     results_obj = compare_rendered_pictures.RenderedPicturesComparisons(
-        setA_dirs=setA_dirs, setB_dirs=setB_dirs,
+        setA_dir=setA_dir, setB_dir=setB_dir,
         setA_section=setA_section, setB_section=setB_section,
         image_diff_db=_SERVER.image_diff_db,
         diff_base_url='/static/generated-images',
         gs=_SERVER.gs, truncate_results=_SERVER.truncate_results,
         prefetch_only=prefetch_only, download_all_images=download_all_images)
     if prefetch_only:
       self.send_response(200)
     else:
       self.send_json_dict(results_obj.get_packaged_results_of_type(
           results_type=results_mod.KEY__HEADER__RESULTS_ALL,
@@ skipping 265 matching lines @@
                    reload_seconds=args.reload, config_pairs=config_pairs,
                    builder_regex_list=args.builders, boto_file_path=args.boto,
                    imagediffdb_threads=args.threads)
   if args.truncate:
     _SERVER.truncate_results = True
   _SERVER.run()
 
 
 if __name__ == '__main__':
   main()