.. method:: ensure_directories(env_dir)
- Creates the environment directory and all necessary directories, and
- returns a context object. This is just a holder for attributes (such as
- paths), for use by the other methods. The directories are allowed to
- exist already, as long as either ``clear`` or ``upgrade`` were
- specified to allow operating on an existing environment directory.
+ Creates the environment directory and all necessary subdirectories that
+ don't already exist, and returns a context object. This context object
+ is just a holder for attributes (such as paths) for use by the other
+ methods. If the :class:`EnvBuilder` is created with the arg
+ ``clear=True``, contents of the environment directory will be cleared
+ and then all necessary subdirectories will be recreated.
.. method:: create_configuration(context)