use std::borrow::BorrowMut; use git_hash::oid;use git_object::TreeRefIter;use git_traverse::tree::breadthfirst; pub trait Sealed {} /// An extension trait for tree iteratorspub trait TreeIterExt: Sealed {    /// Traverse this tree with `state` being provided to potentially reuse allocations, and `find` being a function to lookup trees    /// and turn them into iterators.    ///    /// The `delegate` implements a way to store details about the traversal to allow paying only for what's actually used.    /// Since it is expected to store the operation result, _unit_ is returned.    fn traverse<StateMut, Find, V>(        &self,        state: StateMut,        find: Find,        delegate: &mut V,    ) -> Result<(), breadthfirst::Error>    where        Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Option<TreeRefIter<'a>>,        StateMut: BorrowMut<breadthfirst::State>,        V: git_traverse::tree::Visit;} impl<'d> Sealed for TreeRefIter<'d> {} impl<'d> TreeIterExt for TreeRefIter<'d> {    fn traverse<StateMut, Find, V>(        &self,        state: StateMut,        find: Find,        delegate: &mut V,    ) -> Result<(), breadthfirst::Error>    where        Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Option<TreeRefIter<'a>>,        StateMut: BorrowMut<breadthfirst::State>,        V: git_traverse::tree::Visit,    {        breadthfirst(self.clone(), state, find, delegate)    }}