Implemented rename detection

Using the new RenameDetector class in JGit, I readded rename
detection during in PatchListCacheImpl. It had previously been
removed in change I0adfb7b6 with the switch to JGit. This also
allowed me to remove the costly diff text generation and parsing
that was being done.

Change-Id: I55cbac0ed101acb8a0a64e95555197a92ab15440
1 file changed