Option to split small chains instead of putting on single new line

[vimpunk]

My max_width is 80, using stable version of rustfmt.

E.g. this code I would expect to remain as is:

    let resp = req
        .state()
        .db
        .send(msg)
        .from_err()
        .and_then(|db_resp| match db_resp {
            Ok(roles) => Ok(HttpResponse::Created().json(roles)),
            Err(e) => Err(e),
        });

but is instead formatted like this:

    let resp =
        req.state()
            .db
            .send(msg)
            .from_err()
            .and_then(|db_resp| match db_resp {
                Ok(roles) => Ok(HttpResponse::Created().json(roles)),
                Err(e) => Err(e),
            });

Smaller chains are sometimes kept as a single line but put on a new line, like so:

                let login_ids: Vec<_> =
                    result.active_members.iter().map(|m| m.login_id).collect();

It would be great to have an option to specify that I prefer splitting up such chains instead of keeping them together as much as possible. Apologies if there is already an option for this and I've missed it.