Add a tool that syncs a WebKit git checkout with DEPS.

Review URL: http://codereview.chromium.org/199034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@25543 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 91 insertions, 0 deletions

diff --git a/tools/sync-webkit-git.py b/tools/sync-webkit-git.py
new file mode 100755
index 0000000..0de9d40
--- /dev/null
+++ b/tools/sync-webkit-git.py
@@ -0,0 +1,91 @@
+#!/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.
+
+"""Update third_party/WebKit using git.
+
+Under the assumption third_party/WebKit is a clone of git.webkit.org,
+we can use git commands to make it match the version requested by DEPS.
+
+To use this:
+1) rm -rf third_party/WebKit
+2) git clone git://git.webkit.org/WebKit.git third_party/WebKit
+3) run ./tools/sync-webkit-git.py now, and again whenever you run gclient
+   sync.
+
+FAQ:
+Q. Why not add this functionality to gclient itself?
+A. DEPS actually specifies to only pull some subdirectories of
+   third_party/WebKit.  So even if gclient supported git, we'd still need
+   to special-case this.
+"""
+
+import os
+import subprocess
+import sys
+
+# The name of the magic branch that lets us know that DEPS is managing
+# the update cycle.
+MAGIC_GCLIENT_BRANCH = 'refs/heads/gclient'
+
+def RunGit(command):
+  """Run a git subcommand, returning its output."""
+  proc = subprocess.Popen(['git'] + command, stdout=subprocess.PIPE)
+  return proc.communicate()[0].strip()
+
+def GetWebKitRev():
+  """Extract the 'webkit_revision' variable out of DEPS."""
+  locals = {'Var': lambda _: ''}
+  execfile('DEPS', {}, locals)
+  return locals['vars']['webkit_revision']
+
+def FindSVNRev(rev):
+  """Map an SVN revision to a git hash.
+  Like 'git svn find-rev' but without the git-svn bits."""
+  return RunGit(['rev-list', '-n', '1', '--grep=^git-svn-id: .*@%s' % rev,
+                 'origin'])
+
+def UpdateGClientBranch(webkit_rev):
+  """Update the magic gclient branch to point at |webkit_rev|.
+
+  Returns: true if the branch didn't need changes."""
+  target = FindSVNRev(webkit_rev)
+  if not target:
+    print "r%s not available; fetching." % webkit_rev
+    subprocess.check_call(['git', 'fetch'])
+    target = FindSVNRev(webkit_rev)
+  if not target:
+    print "ERROR: Couldn't map r%s to a git revision." % webkit_rev
+    sys.exit(1)
+
+  current = RunGit(['show-ref', '--hash', MAGIC_GCLIENT_BRANCH])
+  if current == target:
+    return False  # No change necessary.
+
+  subprocess.check_call(['git', 'update-ref', '-m', 'gclient sync',
+                         MAGIC_GCLIENT_BRANCH, target])
+  return True
+
+def UpdateCurrentCheckoutIfAppropriate():
+  """Reset the current gclient branch if that's what we have checked out."""
+  branch = RunGit(['symbolic-ref', '-q', 'HEAD'])
+  if branch != MAGIC_GCLIENT_BRANCH:
+    print "Directory has some other branch ('%s') checked out." % branch
+    print "Run 'git checkout gclient' to put this under control of gclient."
+    return
+
+  if subprocess.call(['git', 'diff-index', '--exit-code', 'HEAD']):
+    print "Resetting tree state to new revision."
+    subprocess.check_call(['git', 'reset', '--hard'])
+
+def main():
+  webkit_rev = GetWebKitRev()
+  print 'Desired revision: r%s.' % webkit_rev
+  os.chdir('third_party/WebKit')
+  changed = UpdateGClientBranch(webkit_rev)
+  if changed:
+    UpdateCurrentCheckoutIfAppropriate()
+
+if __name__ == '__main__':
+  main()