Function href_relative_parts

pub(crate) fn href_relative_parts<'fqp>(
    fqp: &'fqp [Symbol],
    relative_to_fqp: &[Symbol],
) -> Box<dyn Iterator<Item = Symbol> + 'fqp>

Both paths should only be modules. This is because modules get their own directories; that is, std::vec and std::vec::Vec will both need ../iter/trait.Iterator.html to get at the iterator trait.