sort.go
func (s *SortFilter) TextDecreasing(n int) *SortFilter {
	return s.Text(n).flipLast()
}
func (s *SortFilter) TextDecreasing(n int) *SortFilter {
	return s.Text(n).flipLast()
}
// TextDecreasing sets the next sort key to sort by column n in
// reverse lexicographic order. Column 0 means the entire
// string. Items that do not have column n sort to the end.