docs: def context_spec(self):
          """Spec for specifying context options"""
          from harpoon.option_spec import image_objs
          return dict_from_bool_spec(lambda meta, val: {"enabled": val}
              , create_spec(image_objs.Context
                  , validators.deprecated_key("use_git_timestamps", "Since docker 1.8, timestamps no longer invalidate the docker layer cache")
  
                  , include = listof(string_spec())
                  , exclude = listof(string_spec())
                  , enabled = defaulted(boolean(), True)
                  , find_options = string_spec()
  
                  , parent_dir = directory_spec(formatted(defaulted(string_spec(), "{config_root}"), formatter=MergedOptionStringFormatter))
                  , use_gitignore = defaulted(boolean(), False)
                  , ignore_find_errors = defaulted(boolean(), False)
                  )
              )