Suggest owners for OWNERS files that only have per-file owners.

owners.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """A database of OWNERS files.
 
 OWNERS files indicate who is allowed to approve changes in a specific directory
 (or who is allowed to make changes without needing approval of another OWNER).
 Note that all changes must still be reviewed by someone familiar with the code,
 so you may need approval from both an OWNER and a reviewer in many cases.
@@ skipping 139 matching lines @@
                       if not self._is_obj_covered_by(o, covered_objs)]
 
     return set(uncovered_objs)
 
   objects_not_covered_by = directories_not_covered_by
 
   def _check_paths(self, files):
     def _is_under(f, pfx):
       return self.os_path.abspath(self.os_path.join(pfx, f)).startswith(pfx)
     _assert_is_collection(files)
-    assert all(_is_under(f, self.os_path.abspath(self.root)) for f in files)
+    assert all(not self.os_path.isabs(f) and
+                _is_under(f, self.os_path.abspath(self.root)) for f in files)
 
   def _check_reviewers(self, reviewers):
     _assert_is_collection(reviewers)
     assert all(self.email_regexp.match(r) for r in reviewers)
 
   # TODO(dpranke): Rename to _objs_covered_by and update_callers
   def _dirs_covered_by(self, reviewers):
     dirs = self.owned_by[EVERYONE]
     for r in reviewers:
       dirs = dirs | self.owned_by.get(r, set())
@@ skipping 78 matching lines @@
     else:
       raise SyntaxErrorInOwnersFile(owners_path, lineno,
           ('%s is not a "set" directive, "*", '
            'or an email address: "%s"' % (line_type, directive)))
 
 
   def _covering_set_of_owners_for(self, files):
     # Get the set of directories from the files.
     dirs = set()
     for f in files:
-      dirs.add(self.os_path.dirname(f))
+      dirs.add(self._enclosing_dir_with_owners(f))
+
 
     owned_dirs = {}
     dir_owners = {}
 
     for current_dir in dirs:
       # Get the list of owners for each directory.
       current_owners = set()
       dirname = current_dir
       while dirname in self.owners_for:
         current_owners |= self.owners_for[dirname]
@@ skipping 30 matching lines @@
         break
 
       final_owners.add(max_owner)
 
       # Remove all directories owned by the current owner from the remaining
       # list.
       for dirname in owned_dirs[max_owner]:
         dirs.discard(dirname)
 
     return final_owners