improve artifact_feed.author_link index by including field it is sorted on
diff --git a/Allura/allura/model/artifact.py b/Allura/allura/model/artifact.py
index 487530f..4ec0532 100644
--- a/Allura/allura/model/artifact.py
+++ b/Allura/allura/model/artifact.py
@@ -898,7 +898,8 @@
('app_config_id', pymongo.ASCENDING),
('pubdate', pymongo.DESCENDING)),
# used in ext/user_profile/user_main.py for user feeds
- 'author_link',
+ (('author_link', pymongo.ASCENDING),
+ ('pubdate', pymongo.DESCENDING)),
# used in project feed
(('project_id', pymongo.ASCENDING),
('pubdate', pymongo.DESCENDING)),