Add comment to clarify SHOULD_LEAK

tests/fake_repos.py

 #!/usr/bin/python
 # Copyright (c) 2010 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.
 
 """Generate fake repositories for testing."""
 
 import atexit
 import errno
 import logging
@@ skipping 190 matching lines @@
   """Generate both svn and git repositories to test gclient functionality.
 
   Many DEPS functionalities need to be tested: Var, File, From, deps_os, hooks,
   use_relative_paths.
 
   And types of dependencies: Relative urls, Full urls, both svn and git.
 
   populateSvn() and populateGit() need to be implemented by the subclass.
   """
 
-  # Should leak the repositories.
+  # When SHOULD_LEAK is set to True, temporary directories created while the
+  # tests are running aren't deleted at the end of the tests. Expect failures
+  # when running more than one test due to inter-test side-effects. Helps with
+  # debugging.
   SHOULD_LEAK = False
   # Override if unhappy.
   TRIAL_DIR = None
   # Hostname
   HOST = '127.0.0.1'
   NB_GIT_REPOS = 1
   USERS = [
       ('user1@example.com', 'foo'),
       ('user2@example.com', 'bar'),
   ]
@@ skipping 496 matching lines @@
   print 'Using %s' % fake.trial_dir()
   try:
     fake.setUp()
     print('Fake setup, press enter to quit or Ctrl-C to keep the checkouts.')
     sys.stdin.readline()
   except KeyboardInterrupt:
     fake.SHOULD_LEAK = True
   return 0
 
 
-# Kind of hack.
 if '-l' in sys.argv:
+  # See SHOULD_LEAK definition in FakeReposBase for its purpose.
   FakeReposBase.SHOULD_LEAK = True
   print 'Leaking!'
   sys.argv.remove('-l')
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))