add link to previous directory

contour.html

@@ -107,6 +107,10 @@ console.log(data);
         const tree_elt = document.querySelector('#tree');
         if(path) {
             var tree_url = "https://gitlab.constantvzw.org/api/v4/projects/456/repository/tree?path=" + path;
+            previous_path = path.split('/').slice(0, -1).join('/');
+            let li = document.createElement('li');
+            li.innerHTML = "<a href='?path=" + previous_path + "'>..</a>";
+            tree_elt.appendChild(li);
         } else {
             var tree_url = "https://gitlab.constantvzw.org/api/v4/projects/456/repository/tree";
         }