old_contents: #!/usr/bin/env python
  
  import argparse
  import subprocess
  from collections import OrderedDict
  
  
  def main():
      args = get_args()
      local_commits = get_local_commits()
      other_commits = get_other_commits(args.branch, args.path)
      local_subjects = set(local_commits.values())
      for commitish, subject in other_commits.items():
          if subject not in local_subjects:
              print('%s %s' % (commitish, subject))
  
  
  def get_local_commits():
      cmd = [
          'git',
          'log',
          '--format=%h %s',
          '--no-merges',
          '--max-count=2000',
      ]
      return parse_commits(subprocess.check_output(cmd))
  
  
  def get_other_commits(branch, path):
      cmd = [
          'git',
          'log',
          '..%s' % branch,
          '--no-merges',
          '--format=%h %s',
          '--max-count=2000',
      ]
      if path:
          cmd.append('--')
          cmd.append(path)
  
      return parse_commits(subprocess.check_output(cmd))
  
  
  def parse_commits(git_log_output):
      commits = OrderedDict()
      for line in git_log_output.split('\n'):
          line = line.strip()
          if not line:
              continue
          commitish, subject = line.split(' ', 1)
          commits[commitish] = subject
  
      return commits
  
  
  def get_args():
      parser = argparse.ArgumentParser(description='Find commits on a given branch missing '
          'from the current branch')
      parser.add_argument('branch')
      parser.add_argument('path', nargs='?', help='Restrict search by path')
      return parser.parse_args()
  
  
  if __name__ == '__main__':
      main()
  
new_contents: #!/usr/bin/env python
  
  import argparse
  import subprocess
  from collections import OrderedDict
  
  
  def main():
      args = get_args()
      local_commits = get_local_commits()
      other_commits = get_other_commits(args.branch, args.path)
      local_subjects = set(local_commits.values())
      for commitish, subject in other_commits.items():
          if subject not in local_subjects:
              print('%s %s' % (commitish, subject))
  
  
  def get_local_commits():
      cmd = [
          'git',
          'log',
          '--format=%h %s',
          '--no-merges',
          '--max-count=2000',
      ]
      return parse_commits(subprocess.check_output(cmd))
  
  
  def get_other_commits(branch, path):
      cmd = [
          'git',
          'log',
          '..%s' % branch,
          '--no-merges',
          '--format=%h %s',
          '--max-count=2000',
      ]
      if path:
          cmd.append('--')
          cmd.append(path)
  
      return parse_commits(subprocess.check_output(cmd))
  
  
  def parse_commits(git_log_output):
      commits = OrderedDict()
      for line in git_log_output.decode('utf-8').split('\n'):
          line = line.strip()
          if not line:
              continue
          commitish, subject = line.split(' ', 1)
          commits[commitish] = subject
  
      return commits
  
  
  def get_args():
      parser = argparse.ArgumentParser(description='Find commits on a given branch missing '
          'from the current branch')
      parser.add_argument('branch')
      parser.add_argument('path', nargs='?', help='Restrict search by path')
      return parser.parse_args()
  
  
  if __name__ == '__main__':
      main()
  
subject: Make compare_branches py3 compat