Added `cros_pin` CrOS pin-bump tool.

infra/tools/cros_pin/pinfile.py

Index: infra/tools/cros_pin/pinfile.py
diff --git a/infra/tools/cros_pin/pinfile.py b/infra/tools/cros_pin/pinfile.py
new file mode 100644
index 0000000000000000000000000000000000000000..fc6251a243110869787eb48674e1d0e860c964ae
--- /dev/null
+++ b/infra/tools/cros_pin/pinfile.py
@@ -0,0 +1,132 @@
+# Copyright 2015 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 collections
+import contextlib
+import json
+import os
+import re
+
+from infra.libs.gitiles import gitiles
+from infra.tools.cros_pin.logger import LOGGER
+
+class InvalidPinError(Exception):
+  pass
+
+class ReadOnlyError(Exception):
+  pass
+
+
+# Named Chromite pins to their checkout-relative paths.
+Config = collections.namedtuple('Config',
+    ('name', 'base', 'json_subpath', 'masters'))
+
+
+EXTERNAL = Config(
+    'external',
+    ('build',),
+    ('scripts', 'common', 'cros_chromite_pins.json'),
+    ('chromiumos',))
+
+
+INTERNAL = Config(
+    'internal',
+    ('build_internal',),
+    ('scripts', 'common_internal', 'cros_chromite_internal_pins.json'),
+    ('chromeos', 'chromeos_release'))
+
+
+PinUpdate = collections.namedtuple('PinUpdate',
+    ('name', 'fr', 'to'))
+
+
+class Editor(object):
+
+  # Regular expression to match a Git commit (SHA1)
+  RE_COMMIT_SHA1 = re.compile(r'^[a-fA-F0-9]{40}$')
+
+  def __init__(self, checkout_path, gitiles_repo, validate=True):
+    self._checkout_path = checkout_path
+    self._gitiles = None
+    self._validate = validate
+    self._gitiles = gitiles_repo
+
+  def load(self, pin):
+    return self.File(self, pin)
+
+  def get_commit(self, branch):
+    try:
+      return self._gitiles.ref_info(branch)['commit']
+    except gitiles.GitilesError:
+      raise InvalidPinError("Pin ref [%s] does not exist." % (branch,))
+
+  def validate_pin(self, ref):
+    if not self.RE_COMMIT_SHA1.match(ref):
+      raise InvalidPinError("Not a valid SHA1 hash")
+    self.get_commit(ref)
+
+  class File(object):
+    def __init__(self, editor, pin):
+      self._editor = editor
+      self._pin = pin
+      self._path = os.path.join(editor._checkout_path,
+                                *(pin.base + pin.json_subpath))
+
+    @contextlib.contextmanager
+    def edit(self):
+      d = self.load()
+      orig = d.copy()
+      try:
+        yield d
+      finally:
+        if d != orig:
+          self.save(**d)
+
+    def load(self):
+      with open(self._path, 'r') as fd:
+        return json.load(fd)
+
+    def save(self, **pins):
+      for k, v in pins.iteritems():
+        assert isinstance(k, basestring)
+        assert isinstance(v, basestring)
+      LOGGER.debug('Writing pin file [%s]: %s', self._path, pins)
+      with open(self._path, 'w') as fd:
+        json.dump(pins, fd, indent=2, sort_keys=True)
+
+
+    def update(self, pin_name, create=False, version=None):
+      """Updates a single pin value."""
+      if not version:
+        LOGGER.debug('Resolving version for pin [%s]', pin_name)
+        version = self._editor.get_commit(pin_name)
+      elif self._editor._validate:
+        LOGGER.debug('Validating pin [%s]', pin_name)
+        self._editor.validate_pin(version)
+
+      with self.edit() as pins:
+        current = pins.get(pin_name)
+        if current == version:
+          LOGGER.warning('Pin [%s.%s] is already at version [%s]',
+                         self._pin.name, pin_name, current)
+          return None
+
+        LOGGER.info('Updating pin [%s.%s]: [%s] => [%s]',
+                    self._pin.name, pin_name, current, version)
+        if not (current or create):
+          raise ReadOnlyError("Pin does not exist [%s]" % (pin_name,))
+        pins[pin_name] = version
+      return PinUpdate(pin_name, current, version)
+
+    def remove(self, pin_name):
+      """Removes a single pin from the pin list."""
+      with self.edit() as pins:
+        cur = pins.pop(pin_name, None)
+        if cur is None:
+          return None
+      return PinUpdate(pin_name, cur, None)
+
+    def iterpins(self):
+      """Returns a list of pins."""
+      return self.load().iteritems()