Function order_hits 

pub fn order_hits<T>(
    merged: &mut [(T, f32)],
    class: impl Fn(&T) -> (&ResourceKind, Availability),
)

order_by_kind within each Availability::band: every hit the person can open now, ordered as order_by_kind orders them, then the apps they would have to install first, ordered the same way among themselves. Hits of one kind in different bands are separate groups.