fix test-help documentation bug

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1625788 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5945: don't hit NPE on trying to get root's fileName leading to strange test failure

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1625792 13f79535-47bb-0310-9956-ffa450edef68
i before e except after c

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1625795 13f79535-47bb-0310-9956-ffa450edef68