Deleting first IndexCommit

[Jason Rutherglen]

For Ocean I need to be able to delete the latest commit, however currently
using IndexReader.open(final IndexCommit commit, IndexDeletionPolicy
deletionPolicy) I need to open the IndexReader that represents the latest
commit, presumably in IndexDeletionPolicy.onInit delete the IndexCommit,
then close the IndexReader and start over.  Wouldn't this be cleaner to call
IndexReader.listCommits and then delete the first one (assuming they are in
generation descending order).