code: func (s *GitScanner) ScanTree(ref string) error {
  	callback, err := firstGitScannerCallback(s.FoundPointer)
  	if err != nil {
  		return err
  	}
  	return runScanTree(callback, ref, s.Filter)
  }
docs: // ScanTree takes a ref and returns WrappedPointer objects in the tree at that
  // ref. Differs from ScanRefs in that multiple files in the tree with the same
  // content are all reported.