The same check we added earlier to update-cache to catch ENOTDIR
turns out to be missing from diff-files. This causes a
difference not being reported when you have DF/DF (a file in a
subdirectory) in the cache and DF is a file on the filesystem.
Signed-off-by: Junio C Hamano <junkio@cox.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>