message: Path: Make it a context that change current directory.
diff: @@ -555,6 +555,7 @@ class Path:
  self.__str = None
  self.__virtual = virtual
  self.__volume = volume
  + self.__saved_cwd = []
  def canonize(self):
  if self.__canonized is None:
  @@ -1085,6 +1086,14 @@ class Path:
  def __setstate__(self):
  pass
  + def __enter__(self):
  + self.__saved_cwd.append(os.getcwd())
  + os.chdir(str(self))
  + return self
  +
  + def __exit__(self, exc_type, exc_value, traceback):
  + os.chdir(self.__saved_cwd.pop())
  +
  Path.dot = Path('.')
  Path.dotdot = Path('..')
  