diff_tree: disable QUICK optimization with diff filter

We stop looking for changes early with QUICK, so our diff
queue contains only a subset of the changes. However, we
don't apply diff filters until later; it will appear at that
point as though there are no changes matching our filter,
when in reality we simply didn't keep looking for changes
long enough.

Commit 2cfe8a6 (diff --quiet: disable optimization when
--diff-filter=X is used, 2011-03-16) fixes this in some
cases by disabling the optimization when a filter is
present. However, it only tweaked run_diff_files, missing
the similar case in diff_tree. Thus the fix worked only for
diffing the working tree and index, but not between trees.

Noticed by Yasushi SHOJI.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4037-whitespace-status.sh

@@ -67,4 +67,9 @@ test_expect_success 'diff-files --diff-filter --quiet' '
 	test_must_fail git diff-files --diff-filter=M --quiet
 '
 
+test_expect_success 'diff-tree --diff-filter --quiet' '
+	git commit -a -m "worktree state" &&
+	test_must_fail git diff-tree --diff-filter=M --quiet HEAD^ HEAD
+'
+
 test_done

tree-diff.c

@@ -287,6 +287,7 @@ int diff_tree(struct tree_desc *t1, struct tree_desc *t2, const char *base, stru
 
 	for (;;) {
 		if (DIFF_OPT_TST(opt, QUICK) &&
+		    !opt->filter &&
 		    DIFF_OPT_TST(opt, HAS_CHANGES))
 			break;
 		if (opt->nr_paths) {