Docserver: there is only one.

chrome/common/extensions/docs/server2/host_file_system_creator.py

 # Copyright 2013 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.
 
 from caching_file_system import CachingFileSystem
 from local_file_system import LocalFileSystem
 from offline_file_system import OfflineFileSystem
 from subversion_file_system import SubversionFileSystem
 
 class HostFileSystemCreator(object):
   '''Creates host file systems with configuration information. By default, SVN
   file systems are created, although a constructor method can be passed in to
   override this behavior (likely for testing purposes).
   '''
   def __init__(self,
                object_store_creator,
                offline=False,
                constructor_for_test=None):
      self._object_store_creator = object_store_creator
      # Determines whether or not created file systems will be wrapped in an
      # OfflineFileSystem.
      self._offline = offline
      # Provides custom create behavior, useful in tests.
      self._constructor_for_test = constructor_for_test
 
-  def Create(self, branch, revision=None):
+  def Create(self, branch='trunk', revision=None):
     '''Creates either SVN file systems or specialized file systems from the
     constructor passed into this instance. Wraps the resulting file system in
     an Offline file system if the offline flag is set, and finally wraps it in a
     Caching file system.
     '''
     if self._constructor_for_test is not None:
-      file_system = self._constructor_for_test(branch, revision)
+      file_system = self._constructor_for_test(branch=branch, revision=revision)
     else:
-      file_system = SubversionFileSystem.Create(branch, revision=revision)
+      file_system = SubversionFileSystem.Create(branch=branch,
+                                                revision=revision)
     if self._offline:
       file_system = OfflineFileSystem(file_system)
     return CachingFileSystem(file_system, self._object_store_creator)
 
   @staticmethod
   def ForLocal(object_store_creator):
     '''Used in creating a server instance on localhost.
     '''
     return HostFileSystemCreator(
         object_store_creator,
-        constructor_for_test=lambda _, __: LocalFileSystem.Create())
+        constructor_for_test=lambda **_: LocalFileSystem.Create())
 
   @staticmethod
   def ForTest(file_system, object_store_creator):
     '''Used in creating a test server instance. The HostFileSystemCreator
     returned here will always return |file_system| when its Create() method is
     called.
     '''
     return HostFileSystemCreator(
         object_store_creator,
-        constructor_for_test=lambda _, __: file_system)
+        constructor_for_test=lambda **_: file_system)