[Findit] Factoring the gitiles (etc) stuff out into its own directory

appengine/findit/common/chromium_deps.py

 # Copyright 2014 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.
 
 import re
 
+# N.B., in order for our mocking framework to work correctly, we *must not*
+# import the GitRepository class directly; instead, we must only import
+# the git_repository module and then rely on dynamic dispatch to resolve
+# the module's GitRepository attribute. Otherwise the DEPSDownloader.Load
+# method will hold a reference directly to the real GitRepository class,
+# which means we can't swap it out for the DummyGitRepository class, which
+# in turn will cause some unit tests to fail (since we can't mock the
+# responses of doing SSL stuff).
+from lib.gitiles import git_repository
 from common import dependency
 from common import deps_parser
-from common import git_repository
 from common import http_client_appengine
 
 
 _CHROMIUM_ROOT_DIR = 'src/'
 _CHROMIUM_REPO_MASTER = 'https://chromium.googlesource.com/chromium/src.git'
 
 _CHROME_VERSION_PATTERN = re.compile(r'^\d+\.\d+\.\d+\.\d+$')
 
 _BUILDSPEC_REPO = ('https://chrome-internal.googlesource.com/chrome/tools/'
                    'buildspec.git/')
 
 
 def IsChromeVersion(revision):
   """Determines if a revision is a chrome version."""
   if _CHROME_VERSION_PATTERN.match(revision):
     return True
 
   return False
 
 
 class DEPSDownloader(deps_parser.DEPSLoader):
   """Downloads DEPS from remote Git repo."""
 
+  # TODO(wrengr): why do we allocate a new GitRepository every time
+  # we call Load, rather than just doing it once and saving it in the
+  # DEPSDownloader class (via RAII)?
   def Load(self, repo_url, revision, deps_file):
     http_client = http_client_appengine.HttpClientAppengine()
     repo = git_repository.GitRepository(repo_url, http_client)
 
     content = None
     if deps_file == 'DEPS' and repo_url == _CHROMIUM_REPO_MASTER:
       # Try .DEPS.git instead of DEPS first, for commits during the Git chaos.
       content = repo.GetSource('.DEPS.git', revision)
 
     if content is None:
@@ skipping 114 matching lines @@
   """
   deps_rolls = GetChromiumDEPSRolls(old_cr_revision, new_cr_revision, platform,
                                     skip_chromium_roll=False)
 
   deps_rolls_dict = {}
 
   for dep_roll in deps_rolls:
     deps_rolls_dict[dep_roll.path] = dep_roll
 
   return deps_rolls_dict