In index.build_index_from_tree, pass the validate_path_element onto validate_path.

dulwich/index.py

@@ -484,7 +484,7 @@ def build_index_from_tree(prefix, index_path, object_store, tree_id,
     index = Index(index_path)
 
     for entry in object_store.iter_tree_contents(tree_id):
-        if not validate_path(entry.path):
+        if not validate_path(entry.path, validate_path_element):
             continue
         full_path = os.path.join(prefix, entry.path.decode(sys.getfilesystemencoding()))