Bug in "git diff-files"

Hi,

I found a bug in git diff-files.
git diff-files with a --diff-filter and --quiet given behaves bad.
I have a diff-filter of U and one file M and one U.
But diff-lib.c:105-107 in commit 1a9fe45 stops as soon as HAS_CHANGES is 
true.
In my case it found the M file and stops searching as --quiet is given.
But then when applying the diff-filter, this M instance is filtered out 
and thus 0 is returned instead of 1 which is returned with --exit-code 
and without --quiet.

Regards
Björn Kautler