Fix relative file: paths in OWNERS with roots other than '/'

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 81 matching lines @@
 
   This class allows you to find a suggested set of reviewers for a list
   of changed files, and see if a list of changed files is covered by a
   list of reviewers."""
 
   def __init__(self, root, fopen, os_path, glob):
     """Args:
       root: the path to the root of the Repository
       open: function callback to open a text file for reading
       os_path: module/object callback with fields for 'abspath', 'dirname',
-          'exists', and 'join'
+          'exists', 'join', and 'relpath'
       glob: function callback to list entries in a directory match a glob
           (i.e., glob.glob)
     """
     self.root = root
     self.fopen = fopen
     self.os_path = os_path
     self.glob = glob
 
     # Pick a default email regexp to use; callers can override as desired.
     self.email_regexp = re.compile(BASIC_EMAIL_REGEXP)
@@ skipping 172 matching lines @@
     else:
       raise SyntaxErrorInOwnersFile(owners_path, lineno,
           ('%s is not a "set" directive, file include, "*", '
            'or an email address: "%s"' % (line_type, directive)))
 
   def _resolve_include(self, path, start):
     if path.startswith('//'):
       include_path = path[2:]
     else:
       assert start.startswith(self.root)
-      start = self.os_path.dirname(start[len(self.root):])
+      start = self.os_path.dirname(self.os_path.relpath(start, self.root))
       include_path = self.os_path.join(start, path)
 
     owners_path = self.os_path.join(self.root, include_path)
     if not self.os_path.exists(owners_path):
       return None
 
     return include_path
 
   def _covering_set_of_owners_for(self, files, author):
     dirs_remaining = set(self._enclosing_dir_with_owners(f) for f in files)
@@ skipping 52 matching lines @@
   @staticmethod
   def lowest_cost_owner(all_possible_owners, dirs):
     total_costs_by_owner = Database.total_costs_by_owner(all_possible_owners,
                                                          dirs)
     # Return the lowest cost owner. In the case of a tie, pick one randomly.
     lowest_cost = min(total_costs_by_owner.itervalues())
     lowest_cost_owners = filter(
         lambda owner: total_costs_by_owner[owner] == lowest_cost,
         total_costs_by_owner)
     return random.Random().choice(lowest_cost_owners)