Function resolve_tree_path 

pub fn resolve_tree_path<S: ObjectSource>(
    store: &S,
    root: &ContentHash,
    path: &Path,
    policy: LeafPolicy,
) -> Result<Option<ResolvedTreeTarget>, TreePathResolveError>

Walk path from root through nested subtrees and resolve the terminal entry according to policy.

Ok(None) means the path is absent or terminates at the wrong entry type for the policy. Store failures and missing subtrees are policy-dependent; see TreePathResolveError.