IndexDatabase.getFiles() functionality needs to be investigated

[vladak]

When working on test case for #767 I wanted to peruse modified version (so that it returns set of strings instead of writing them to the log) of IndexDatabase#listFiles() and call it like this:

Assert.assertEquals(6, idb.getFiles().size());

however got exception instead:

Testcase: testCleanupAfterIndexRemoval(org.opensolaris.opengrok.index.IndexDatabaseTest):	Caused an ERROR
String index out of range: -1
java.lang.StringIndexOutOfBoundsException: String index out of range: -1
	at java.lang.String.substring(String.java:1967)
	at org.opensolaris.opengrok.web.Util.uid2url(Util.java:647)
	at org.opensolaris.opengrok.index.IndexDatabase.getFiles(IndexDatabase.java:1028)
	at org.opensolaris.opengrok.index.IndexDatabaseTest.testCleanupAfterIndexRemoval(IndexDatabaseTest.java:164)

This is curious feature anyway that is being called from Indexer#prepareIndexer:

789          if (listFiles) {
790              IndexDatabase.listAllFiles(subFiles);
791          }

however the listFiles boolean does not have a matching command line option and is set to false by default so likely this code path has not been called for a long time. Hence filing this issue so that it is not forgotten. Either it should be fixed or ripped out.

[vladak]

Same code for terms traversal is used in IndexDatabase#update() and looks correct according to https://stackoverflow.com/questions/15290980/how-to-get-all-terms-for-a-lucene-field-in-lucene-4 so maybe this was something special about the test testCleanupAfterIndexRemoval() in cset d3dbeac - try to replace the call to idb.getNumFiles() with getFiles().size().