Unpack an image into a directory structure

    CLI Example:

    .. code-block:: bash

        salt myminion genesis.unpack centos /root/centos

def unpack(name, dest=None, path=None, pack_format='tar', compress='bz2'):
    '''
    Unpack an image into a directory structure

    CLI Example:

    .. code-block:: bash

        salt myminion genesis.unpack centos /root/centos
    '''
    if pack_format == 'tar':
        _untar(name, dest, path, compress)