git_cache: Remove locks

These aren't in use, and the original problem they were
meant to solve has been solved at the gclient.py layer 
using resource locking:
  https://codereview.chromium.org/2049583003

Bug: 773008
Change-Id: I6609f39d7f15604e0bb3d742a41c4f9fec87a57a
Reviewed-on: https://chromium-review.googlesource.com/707728Reviewed-by: Aaron Gable <agable@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Ryan Tseng <hinoka@chromium.org>

gclient.py

@@ -1308,10 +1308,6 @@ it or fix the checkout.
     if cache_dir:
       cache_dir = os.path.join(self.root_dir, cache_dir)
       cache_dir = os.path.abspath(cache_dir)
-      # If running on a bot, force break any stale git cache locks.
-      if os.path.exists(cache_dir) and os.environ.get('CHROME_HEADLESS'):
-        subprocess2.check_call(['git', 'cache', 'unlock', '--cache-dir',
-                                cache_dir, '--force', '--all'])
     gclient_scm.GitWrapper.cache_dir = cache_dir
     git_cache.Mirror.SetCachePath(cache_dir)
 
@@ -2354,16 +2350,11 @@ def CMDsync(parser, args):
   parser.add_option('--no_bootstrap', '--no-bootstrap',
                     action='store_true',
                     help='Don\'t bootstrap from Google Storage.')
-  parser.add_option('--ignore_locks', action='store_true',
-                    help='GIT ONLY - Ignore cache locks.')
   parser.add_option('--break_repo_locks', action='store_true',
                     help='GIT ONLY - Forcibly remove repo locks (e.g. '
                       'index.lock). This should only be used if you know for '
                       'certain that this invocation of gclient is the only '
                       'thing operating on the git repos (e.g. on a bot).')
-  parser.add_option('--lock_timeout', type='int', default=5000,
-                    help='GIT ONLY - Deadline (in seconds) to wait for git '
-                         'cache lock to become available. Default is %default.')
   # TODO(agable): Remove these when the oldest CrOS release milestone is M56.
   parser.add_option('-t', '--transitive', action='store_true',
                     help='DEPRECATED: This is a no-op.')

gclient_scm.py

@@ -855,10 +855,7 @@ class GitWrapper(SCMWrapper):
       depth = None
     mirror.populate(verbose=options.verbose,
                     bootstrap=not getattr(options, 'no_bootstrap', False),
-                    depth=depth,
-                    ignore_lock=getattr(options, 'ignore_locks', False),
-                    lock_timeout=getattr(options, 'lock_timeout', 0))
-    mirror.unlock()
+                    depth=depth)
 
   def _Clone(self, revision, url, options):
     """Clone a git repository from the given URL.

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -331,7 +331,7 @@ def gclient_sync(
   os.close(fd)
 
   args = ['sync', '--verbose', '--reset', '--force',
-         '--ignore_locks', '--output-json', gclient_output_file,
+         '--output-json', gclient_output_file,
          '--nohooks', '--noprehooks', '--delete_unversioned_trees']
   if with_branch_heads:
     args += ['--with_branch_heads']
@@ -470,36 +470,9 @@ def is_broken_repo_dir(repo_dir):
   return not path.exists(os.path.join(repo_dir, '.git', 'config'))
 
 
-def _maybe_break_locks(checkout_path):
-  """This removes all .lock files from this repo's .git directory.
-
-  In particular, this will cleanup index.lock files, as well as ref lock
-  files.
-  """
-  git_dir = os.path.join(checkout_path, '.git')
-  for dirpath, _, filenames in os.walk(git_dir):
-    for filename in filenames:
-      if filename.endswith('.lock'):
-        to_break = os.path.join(dirpath, filename)
-        print 'breaking lock: %s' % to_break
-        try:
-          os.remove(to_break)
-        except OSError as ex:
-          print 'FAILED to break lock: %s: %s' % (to_break, ex)
-          raise
-
-
 def git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
                  cleanup_dir):
   build_dir = os.getcwd()
-  # Before we do anything, break all git_cache locks.
-  if path.isdir(git_cache_dir):
-    git('cache', 'unlock', '-vv', '--force', '--all',
-        '--cache-dir', git_cache_dir)
-    for item in os.listdir(git_cache_dir):
-      filename = os.path.join(git_cache_dir, item)
-      if item.endswith('.lock'):
-        raise Exception('%s exists after cache unlock' % filename)
   first_solution = True
   for sln in solutions:
     # Just in case we're hitting a different git server than the one from
@@ -516,7 +489,7 @@ def git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
         shallow = False
       sln_dir = path.join(build_dir, name)
       s = ['--shallow'] if shallow else []
-      populate_cmd = (['cache', 'populate', '--ignore_locks', '-v',
+      populate_cmd = (['cache', 'populate', '-v',
                        '--cache-dir', git_cache_dir] + s + [url])
       for ref in refs:
         populate_cmd.extend(['--ref', ref])
@@ -544,18 +517,6 @@ def git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
           refspec = '%s:%s' % (ref, ref.lstrip('+'))
           git('fetch', 'origin', refspec, cwd=sln_dir)
 
-        # Windows sometimes has trouble deleting files.
-        # This can make git commands that rely on locks fail.
-        # Try a few times in case Windows has trouble again (and again).
-        if sys.platform.startswith('win'):
-          tries = 3
-          while tries:
-            try:
-              _maybe_break_locks(sln_dir)
-              break
-            except Exception:
-              tries -= 1
-
         revision = get_target_revision(name, url, revisions) or 'HEAD'
         force_revision(sln_dir, revision)
         done = True

tests/bot_update_coverage_test.py

@@ -231,20 +231,6 @@ class BotUpdateUnittests(unittest.TestCase):
         gclient_sync_cmd = args
     self.assertTrue('--break_repo_locks' in gclient_sync_cmd)
 
-  def testGitCheckoutBreaksLocks(self):
-    self.overrideSetupForWindows()
-    path = '/b/build/slave/foo/build/.git'
-    lockfile = 'index.lock'
-    removed = []
-    old_os_walk = os.walk
-    old_os_remove = os.remove
-    setattr(os, 'walk', lambda _: [(path, None, [lockfile])])
-    setattr(os, 'remove', removed.append)
-    bot_update.ensure_checkout(**self.params)
-    setattr(os, 'walk', old_os_walk)
-    setattr(os, 'remove', old_os_remove)
-    self.assertTrue(os.path.join(path, lockfile) in removed)
-
 
 if __name__ == '__main__':
   unittest.main()