Function desired_set 

pub fn desired_set<P, C>(
    entries: impl IntoIterator<Item = (P, C)>,
) -> BTreeMap<String, ContentHash>
where
    P: Into<String>,
    C: AsRef<[u8]>,

Build the desired path -> content_hash set for a working tree by hashing each file’s content. The output feeds Manifest::reconcile.