wrapUnderlyingReader
Given an IndexSearcher, returns a new IndexSearcher whose IndexReader is a MultiReader containing the Reader of the original IndexSearcher, as well as several "empty" IndexReaders -- some of which will have deleted documents in them. This new IndexSearcher should behave exactly the same as the original IndexSearcher.
Parameters
s
the searcher to wrap
edge
if negative, s will be the first sub; if 0, s will be in the middle, if positive s will be the last sub