def _pkg(jail=None, chroot=None, root=None):
    '''
    Returns the prefix for a pkg command, using -j if a jail is specified, or
    -c if chroot is specified.
    '''
    ret = ['pkg']
    if jail:
        ret.extend(['-j', jail])
    elif chroot:
        ret.extend(['-c', chroot])
    elif root:
        ret.extend(['-r', root])
    return ret
Returns the prefix for a pkg command, using -j if a jail is specified, or
    -c if chroot is specified.