Add git-cl upload hooks.

Provide git-cl upload and dcommit hooks based on this
single hooks file.  Installed via git-cl config.
Loads and calls the PresubmitSupport library.
Test failure before a dcommit halts the check-in.

BUG=5339
TEST=hooks file runs presubmit checks and halts
checkin (dcommit) or repeats error messages (upload).
hooks file runs and doesn't interrupt process if no
errors present.
Review URL: http://codereview.chromium.org/256075

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@28125 0039d316-1c4b-4281-b951-d872f2087c98

git-cl-upload-hook

+#!/usr/bin/python
+# Copyright (c) 2009 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 os
+import re
+import subprocess
+import sys
+
+# Find depot_tools in PATH, append it to sys.path so we can import.
+paths = os.environ.get("PATH")
+for path in paths.split(':'):
+  if not path.endswith("depot_tools"):
+    continue
+  sys.path.append(path)
+  break
+
+import gclient_scm
+import presubmit_support
+
+def Backquote(cmd, cwd=None):
+  """Like running `cmd` in a shell script."""
+  return subprocess.Popen(cmd,
+                          cwd=cwd,
+                          stdout=subprocess.PIPE).communicate()[0].strip()
+
+
+class ChangeOptions:
+  def __init__(self, commit=None, upstream_branch=None):
+    self.commit = commit
+    self.verbose = None
+    self.default_presubmit = None
+    self.may_prompt = None
+
+    root = os.path.abspath(Backquote(['git', 'rev-parse', '--show-cdup']))
+    if not root:
+      raise Exception("Could not get root directory.")
+    log = Backquote(['git', 'show', '--name-only',
+                     '--pretty=format:%H%n%s%n%n%b'])
+    m = re.match(r'^(\w+)\n(.*)$', log, re.MULTILINE|re.DOTALL)
+    if not m:
+      raise Exception("Could not parse log message: %s" % log)
+    name = m.group(1)
+    description = m.group(2)
+    files = gclient_scm.CaptureGitStatus([root], upstream_branch)
+    issue = Backquote(['git', 'cl', 'status', '--field=id'])
+    patchset = None
+    self.change = presubmit_support.GitChange(name, description, root, files,
+                                              issue, patchset)
+
+
+# Ensure we were called with the necessary number of arguments.
+program_name = os.path.basename(sys.argv[0])
+if len(sys.argv) < 2:
+  raise Exception("usage: %s [upstream branch]" % program_name)
+
+# Get arguments from how we were called.
+commit = (program_name == 'pre-cl-dcommit')
+upstream_branch = sys.argv[1]
+
+# Create our options based on the command-line args and the current checkout.
+options = ChangeOptions(commit=commit, upstream_branch=upstream_branch)
+
+# Run the presubmit checks.
+if presubmit_support.DoPresubmitChecks(options.change,
+                                       options.commit,
+                                       options.verbose,
+                                       sys.stdout,
+                                       sys.stdin,
+                                       options.default_presubmit,
+                                       options.may_prompt):
+  sys.exit(0)
+else:
+  sys.exit(1)