When sorting, lump rollup=never and rollup=maybe

When determining the sort order for pull requests, always sort
`rollup=always` to the bottom of the list, and ignore any other rollup
status.

Previously, a PR with `priority=0`, `rollup=never` would be in the queue
above a PR with `priority=1`, `rollup=maybe`. This commit makes it so
that PRs with `rollup=never` is **not** given higher weight than
`rollup-maybe`, so the `priority=1` pull will rank higher.

Fixes #27

Author: bryanburgers

homu/main.py

@@ -180,7 +180,9 @@ def sort_key(self):
             STATUS_TO_PRIORITY.get(self.get_status(), -1),
             1 if self.mergeable is False else 0,
             0 if self.approved_by else 1,
-            self.rollup,
+            # Sort rollup=always to the bottom of the queue, but treat all
+            # other rollup statuses as equivalent
+            1 if WORDS_TO_ROLLUP['rollup=always'] == self.rollup else 0,
             -self.priority,
             self.num,
         ]