tree rename dialog - focus filename without extension

focus only the relevant part of the filename on rename dialog
this selects all prior to the first dot in the filename

notebook/static/tree/js/notebooklist.js

@@ -663,7 +663,12 @@ define([
                         return false;
                     }
                 });
-                input.focus().select();
+                input.focus();
+                if (input.val().indexOf(".") > 0) {
+                    input[0].setSelectionRange(0,input.val().indexOf("."));
+                } else {
+                    input.select();
+                }
             }
         });
     };