Returns the arguments parsed from *argv* as a namespace.

def parse_commandline(argv):
  """
  Returns the arguments parsed from *argv* as a namespace.

  """
  ap = ArgumentParser(
    prog='wdiffhtml',
    description=DESCRIPTION,
    epilog=EPILOG,
  )
  ap.add_argument(
    '--version', action='version', version='wdiffhtml v{}'.format(version),
    help="shows version and exits"
  )
  ap.add_argument(
    'org_file', metavar='FILENAME',
    help="original file"
  )
  ap.add_argument(
    'new_file', metavar='FILENAME',
    help="changed file"
  )
  g_html = ap.add_argument_group(
    'Wrapper',
    "Without these settings, only the `wdiff` output is returned (with INS "
    "and DEL tags). Here are some options to wrap the output in a HTML "
    "document."
  )
  g_html.add_argument(
    '-w', '--wrap-with-html', action='store_true',
    help="wrap the diff with a HTML document"
  )
  g_html.add_argument(
    '-f', '--fold-tags', action='store_true',
    help="allow INS and DEL tags to span linebraks"
  )
  g_html.add_argument(
    '-b', '--hard-breaks', action='store_true',
    help="replace line breaks with BR tags"
  )
  g_context = ap.add_argument_group(
    'Context',
    "With these options you can add additional information to the HTML "
    "output (means these only work alongside the `--wrap-with-html` option)."
  )
  g_context.add_argument(
    '-r', '--revision', metavar='STRING',
    help="add a revision tag or version number to the output"
  )
  x_stamp = g_context.add_mutually_exclusive_group()
  x_stamp.add_argument(
    '-d', '--datestamp', action='store_true',
    help="add a date to the output (UTC now)"
  )
  x_stamp.add_argument(
    '-D', '--timestamp', action='store_true',
    help="add date and time to the output (UTC now)"
  )
  g_files = ap.add_argument_group(
    'Files',
    "Instead of using the default templates, you can use your own files. "
    "These only work alongside the `--wrap-with-html` option"
  )
  g_files.add_argument(
    '-t', '--template', type=FileType('r'), metavar='FILE',
    help="load the Jinja2 template from this file"
  )
  g_files.add_argument(
    '-c', '--css', type=FileType('r'), metavar='FILE',
    help="load CSS from this file"
  )
  g_files.add_argument(
    '-j', '--js', type=FileType('r'), metavar='FILE',
    help="load Javascript from this file"
  )
  g_files.add_argument(
    '-J', '--js2', type=FileType('r'), metavar='FILE',
    help="load another Javascript from this file (like Zepto)"
  )
  # parse args
  args = ap.parse_args(argv)
  # check for wrapper
  if not args.wrap_with_html:
    # check context arguments and file arguments
    for group in (g_context, g_files):
      args_to_check = [opt.dest for opt in group._group_actions]
      if any([getattr(args, attr) for attr in args_to_check]):
        msg = "the options require that `--wrap-with-html` is used"
        ap.error(msg)
  return args