Function finalize_cherry_pick_message 

pub fn finalize_cherry_pick_message(
    original_message: &str,
    append_source: bool,
    signoff: bool,
    committer_name: &str,
    committer_email: &str,
    config: &ConfigSet,
    picked_commit_hex: &str,
) -> String

Apply -x / -s rewriting plus optional commit.cleanup when -x is set.