Re: [PATCH v2] git-diff: Output a warning about stale files in the index

Actually this is wrong in two points:

 * The filtering should be done upfront at the beginning of the
   diffcore_std(), not before the end.  Otherwise, unchanged but
   cache dirty file could be subject to copy detection.

 * I do not think it should affect the low-level git-diff-* (or
   you should update the tests, documentations and perhaps
   whatever people can find from google).

By the way, I had an updated version of my patch to fix the
first point on 'pu' for a while.