def __init__(self, root_dir, parser, argv):
    Command.__init__(self, root_dir, parser, argv)

    if len(self.args) is not 1:
      self.error("Exactly one BUILD address is required.")

    spec = self.args[0]
    try:
      address = Address.parse(root_dir, spec)
    except IOError:
      self.error("Problem parsing spec %s: %s" % (spec, traceback.format_exc()))

    try:
      self.target = Target.get(address)
    except (ImportError, SyntaxError, TypeError):
      self.error("Problem parsing BUILD target %s: %s" % (address, traceback.format_exc()))

    if not self.target:
      self.error("Target %s does not exist" % address)

def _synthesize_command(root_dir, args):
  command = args[0]

  if command in Command.all_commands():
    subcommand_args = args[1:] if len(args) > 1 else []
    return command, _add_default_options(command, subcommand_args)

  if command.startswith('-'):
    _exit_and_fail('Invalid command: %s' % command)

  # assume 'build' if a command was omitted.
  try:
    Address.parse(root_dir, command)
    return _BUILD_COMMAND, _add_default_options(_BUILD_COMMAND, args)
  except:
    _exit_and_fail('Failed to execute pants build: %s' % traceback.format_exc())

 def __init__(self, root_dir, parser, args):
   self.targets = []
   Command.__init__(self, root_dir, parser, args)

 def __init__(self, root_dir, parser, args):
   self.targets = []
   # Note that we can't gate this on the self.options.time flag, because self.options is
   # only set up in Command.__init__, and only after it calls setup_parser(), which uses the timer.
   self.timer = Timer()
   Command.__init__(self, root_dir, parser, args)

def _find_all_commands():
  for cmd in Command.all_commands():
    cls = Command.get_command(cmd)
    yield '%s\t%s' % (cmd, cls.__doc__)

def _parse_command(root_dir, args):
  command, args = _synthesize_command(root_dir, args)
  return Command.get_command(command), args