Function plain_instead 

pub fn plain_instead(connection: &str) -> bool

Whether a durable pane on connection runs as a plain SSH terminal instead, because the user doesn’t want the helper there (§4.9: “Not now, or Never: the pane falls back”): the host is set to Never, or the user answered “Not now” for it since srv started. Set to Always, never. Also a host the helper can’t run on (a Windows host), whatever the setting.