try {
Journal journal = backup.getJournal("root");
SegmentNodeState state = new SegmentNodeState(
backup.getWriter().getDummySegment(), journal.getHead());
SegmentNodeBuilder builder = state.builder();
String beforeCheckpoint = state.getString("checkpoint");
if (beforeCheckpoint == null) {
// 3.1 no stored checkpoint, so do the initial full backup
builder.setChildNode("root", current);