blink_rename_merge_helper: Implement run.py loader stub

tools/blink_rename_merge_helper/run.py

Index: tools/blink_rename_merge_helper/run.py
diff --git a/tools/blink_rename_merge_helper/run.py b/tools/blink_rename_merge_helper/run.py
new file mode 100755
index 0000000000000000000000000000000000000000..293fc409b415528047993020bf0fcf1cd1c56150
--- /dev/null
+++ b/tools/blink_rename_merge_helper/run.py
@@ -0,0 +1,146 @@
+#!/usr/bin/env python
+# Copyright 2017 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.
+"""Tool to help developers rebase branches across the Blink rename."""
+
+import json
+import os
+import subprocess
+import shutil
+import sys
+import tempfile
+
+
+class _DepotToolsNotFoundException(Exception):
+  pass
+
+
+def _whereis(name):
+  """Find and return the first entry in $PATH containing a file named |name|.
+
+  Returns the path if found; otherwise returns nothing.
+  """
+  for path in os.environ['PATH'].split(os.pathsep):
+    if os.path.exists(os.path.join(path, name)):
+      return path
+
+
+def _find_depot_tools():
+  """Attempts to configure and return a wrapper for invoking depot tools.
+
+  Returns:
+    A helper object for invoking depot tools.
+
+  Raises:
+    _DepotToolsNotFoundException: An error occurred trying to find depot tools.
+  """
+
+  class DepotToolsWrapper(object):
+
+    def __init__(self, path):
+      self.__download_from_google_storage = os.path.join(
+          path, 'download_from_google_storage.py')
+      self.__gsutil = os.path.join(path, 'gsutil.py')
+
+    def call_download_from_google_storage(self, *args):
+      """Runs download_from_google_storage with the given args."""
+      subprocess.check_call(['python', self.__download_from_google_storage] +
+                            list(args))
+
+    def call_gsutil(self, *args):
+      """Runs gsutil with the given args."""
+      subprocess.check_call(['python', self.__gsutil] + list(args))
+
+  # Attempt to find download_from_google_storage.py from depot_tools
+  path = _whereis('download_from_google_storage.py')
+  if not path:
+    raise _DepotToolsNotFoundException(
+        'download_from_google_storage.py not found. Make sure depot_tools is '
+        'in $PATH.')
+
+  # Make sure gsutil.py is in the same location
+  path2 = _whereis('download_from_google_storage.py')
+  if not path2:
+    raise _DepotToolsNotFoundException(
+        'gsutil.py not found. Make sure depot_tools is in $PATH.')
+
+  if path != path2:
+    raise _DepotToolsNotFoundException(
+        'download_from_google_storage.py found in %s but gsutil.py found in %s.'
+        % (path, path2))
+
+  return DepotToolsWrapper(path)
+
+
+class Bootstrapper(object):
+  """Helper class for bootstrapping startup of the rebase helper.
+
+  Performs update checks and stages any required binaries."""
+
+  def __init__(self, depot_tools):
+    """Bootstrapper constructor.
+
+    Args:
+      depot_tools: a wrapper for invoking depot_tools.
+    """
+    self.__depot_tools = depot_tools
+    self.__tmpdir = None
+
+  def __enter__(self):
+    self.__tmpdir = tempfile.mkdtemp()
+    return self
+
+  def __exit__(self, exc_type, exc_value, traceback):
+    shutil.rmtree(self.__tmpdir, ignore_errors=True)
+
+  def update(self):
+    """Performs an update check for various components."""
+    components = self._get_latest_components()
+    for name, sha1_hash in components.iteritems():
+      args = [
+          '--no_auth', '--no_resume', '-b', 'chromium-blink-rename',
+          '--extract', sha1_hash
+      ]
+      if '-' in name:
+        name, platform = name.split('-', 1)
+        args.append('-p')
+        args.append(platform)
+      args.append('-o')
+      args.append(os.path.join('staging', '%s.tar.gz' % name))
+      self.__depot_tools.call_download_from_google_storage(*args)
+
+  def _get_latest_components(self):
+    """Fetches info about the latest components from google storage.
+
+    The return value should be a dict of component names to SHA1 hashes."""
+    hashes_path = os.path.join(self.__tmpdir, 'COMPONENTS')
+    self.__depot_tools.call_gsutil(
+        'cp', 'gs://chromium-blink-rename/COMPONENTS', hashes_path)
+    with open(hashes_path) as f:
+      return json.loads(f.read())
+
+
+def main():
+  script_dir = os.path.dirname(os.path.realpath(__file__))
+  os.chdir(script_dir)
+
+  try:
+    depot_tools = _find_depot_tools()
+  except _DepotToolsNotFoundException as e:
+    print e.message
+    return 1
+
+  print 'Checking for updates...'
+  with Bootstrapper(depot_tools) as bootstrapper:
+    bootstrapper.update()
+
+  # Import stage 2 and launch it.
+  tool_pylib = os.path.abspath(os.path.join(script_dir, 'staging/pylib'))
+  sys.path.insert(0, tool_pylib)
+  from blink_rename_merge_helper import driver
+  driver.run()
+
+
+if __name__ == '__main__':
+  sys.exit(main())