Add safely-roll-webkit.py to streamline webkit rolls.

tools/safely-roll-webkit.py

Index: tools/safely-roll-webkit.py
diff --git a/tools/safely-roll-webkit.py b/tools/safely-roll-webkit.py
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+++ b/tools/safely-roll-webkit.py
@@ -0,0 +1,81 @@
+#!/usr/bin/env python
+# Copyright (c) 2011 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.
+
+"""Safely* rolls webkit.
+
+* As safely as currently possible.
+"""

[Dirk Pranke, 2011/05/30 21:23:24]

This comment isn't that helpful. I would replace it with something like:

Generate a CL to roll webkit to the specified revision number and post it to
Rietveld so that the CL will land automatically if it passes the commit-queue's
checks.

[M-A Ruel, 2011/05/31 01:21:07]

done

+
+import logging
+import optparse
+import os
+import re
+import sys
+
+import find_depot_tools
+import scm
+import subprocess2
+
+
+def die_with_error(msg):
+  print >> sys.stderr, msg
+  sys.exit(1)
+
+
+def process_deps(path, new_rev):
+  """Update webkit_revision to |new_issue|.
+
+  A bit hacky, could it be made better?
+  """
+  content = open(path).read()
+  old_line = r'  "webkit_revision": "(\d+)",'
+  new_line = '  "webkit_revision": "%d",' % new_rev

[Dirk Pranke, 2011/05/30 21:23:24]

Hm. I'd probably do this using readlines() for line-at-a-time parsing and then
match against and update a single line. 

At the very least, I'd want to explicitly match against the beginning of the
line using ^\s+ instead of the '  ' that you have now (and also match against
the end of the line using $).

Your code could get confused (I think) by having comments elsewhere in the DEPS
file that refer to "webkit_revision: 3"  or something else like that.

[M-A Ruel, 2011/05/31 01:21:07]

I prefer to keep the dumb logic here and change it if needed. I added count=1 so
only one replacement is done. I changed the code below to print the diff so it
will pause if the diff is too long.

+  new_content = re.sub(old_line, new_line, content)
+  if new_content == content:
+    die_with_error('Failed to update the DEPS file')
+  open(path, 'w').write(new_content)
+
+
+def main():
+  tool_dir = os.path.dirname(os.path.abspath(__file__))
+  parser = optparse.OptionParser(usage='<new webkit rev>')
+  parser.add_option('-v', '--verbose', action='count', default=0)
+  options, args = parser.parse_args()
+  logging.basicConfig(
+      level=
+          [logging.WARNING, logging.INFO, logging.DEBUG][
+            min(2, options.verbose)])
+  if len(args) != 1:
+    parser.error('Need only one arg: new webkit revision to roll to.')
+
+  root_dir = os.path.dirname(tool_dir)
+  os.chdir(root_dir)
+
+  new_rev = int(args[0])
+  msg = 'Roll webkit revision to %s' % new_rev
+  print msg
+
+  # Silence the editor.
+  os.environ['EDITOR'] = '/bin/true'
+
+  old_branch = scm.GIT.GetBranch(root_dir)
+  subprocess2.check_output(
+      ['git', 'checkout', '-b', 'webkit_roll', 'origin/trunk'])
+  try:
+    process_deps(os.path.join(root_dir, 'DEPS'), new_rev)
+    subprocess2.check_output(['git', 'commit', '-m', msg, 'DEPS'])
+    changed = subprocess2.check_output(
+        ['git', 'diff', 'origin/trunk', '--name-only']).splitlines()
+    if changed != ['DEPS']:
+      die_with_error('Make sure to be on a clean branch first')
+    subprocess2.check_call(['git', 'cl', 'upload', '--use-commit-queue'])
+  finally:
+    subprocess2.check_output(['git', 'checkout', old_branch])
+    subprocess2.check_output(['git', 'branch', '-D', 'webkit_roll'])

[Dirk Pranke, 2011/05/30 21:23:24]

I personally don't like to delete branches until after the change has landed. I
wonder if it makes sense to provide for that, or (more generally) a way to break
this up into each step?

On the other hand, making this extremely simple and idiot-proof is probably a
good thing for now. You can always make it more flexible later.

[M-A Ruel, 2011/05/31 01:21:07]

By using check_call(git checkout -b) before the try block, it will return 1 if
the branch already existed or if uncommitted files would be touched so this is
quite safe. Also, the branch is directly done against upstream and not the
current branch.

+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())