text: #!/usr/bin/env python
  # 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.
  
  """Print statistics about the rate of commits to a repository."""
  
  import datetime
  import itertools
  import json
  import math
  import urllib
  import urllib2
  
  
  _BASE_URL = 'https://chromium.googlesource.com'
  # Can be up to 10,000.
  _REVISION_COUNT = 1000
  
  _REPOSITORIES = [
      'chromium/src',
      'angle/angle',
      'skia',
      'v8/v8',
  ]
  
  
  def Pairwise(iterable):
    """s -> (s0,s1), (s1,s2), (s2, s3), ..."""
    a, b = itertools.tee(iterable)
    next(b, None)
    return itertools.izip(a, b)
  
  
  def Percentile(data, percentile):
    """Find a percentile of a list of values.
  
    Parameters:
      data: A sorted list of values.
      percentile: The percentile to look up, from 0.0 to 1.0.
  
    Returns:
      The percentile.
  
    Raises:
      ValueError: If data is empty.
    """
    if not data:
      raise ValueError()
  
    k = (len(data) - 1) * percentile
    f = math.floor(k)
    c = math.ceil(k)
  
    if f == c:
      return data[int(k)]
    return data[int(f)] * (c - k) + data[int(c)] * (k - f)
  
  
  def CommitTimes(repository, revision_count):
    parameters = urllib.urlencode((('n', revision_count), ('format', 'JSON')))
    url = '%s/%s/+log?%s' % (_BASE_URL, urllib.quote(repository), parameters)
    data = json.loads(''.join(urllib2.urlopen(url).read().splitlines()[1:]))
  
    commit_times = []
    for revision in data['log']:
      commit_time_string = revision['committer']['time']
      commit_time = datetime.datetime.strptime(
          commit_time_string, '%a %b %d %H:%M:%S %Y')
      commit_times.append(commit_time)
  
    return commit_times
  
  
  def main():
    for repository in _REPOSITORIES:
      commit_times = CommitTimes(repository, _REVISION_COUNT)
  
      commit_durations = []
      for time1, time2 in Pairwise(commit_times):
        commit_durations.append((time1 - time2).total_seconds())
      commit_durations.sort()
  
      print 'REPOSITORY:', repository
      print 'Start Date:', min(commit_times)
      print '  End Date:', max(commit_times)
      print '  Duration:', max(commit_times) - min(commit_times)
      print '         n:', len(commit_times)
  
      for p in (0.00, 0.05, 0.25, 0.50, 0.75, 0.95, 1.00):
        percentile = Percentile(commit_durations, p)
        print '%3d%% commit duration:' % (p * 100), '%6ds' % percentile
      mean = math.fsum(commit_durations) / len(commit_durations)
      print ' Min commit duration:', '%6ds' % min(commit_durations)
      print 'Mean commit duration:', '%6ds' % mean
      print ' Max commit duration:', '%6ds' % max(commit_durations)
      print
  
  
  if __name__ == '__main__':
    main()
  