After "git add -N", the path appeared in output of "git diff HEAD"
and "git diff --cached HEAD", leading "git status" to classify it
as "Changes to be committed".  Such a path, however, is not yet to
be scheduled to be committed.  "git diff" showed the change to the
path as modification, not as a "new file", in the header of its
output.

Treat such paths as "yet to be added to the index but Git already
know about them"; "git diff HEAD" and "git diff --cached HEAD"
should not talk about them, and "git diff" should show them as new
files yet to be added to the index.

* nd/diff-i-t-a:
  diff-lib.c: adjust position of i-t-a entries in diff