filter-branch: use git rev-parse -q

Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-filter-branch.sh

@@ -256,7 +256,7 @@ while read commit parents; do
 	*)
 		# The commit may not have the subdirectory at all
 		err=$(git read-tree -i -m $commit:"$filter_subdir" 2>&1) || {
-			if ! git rev-parse --verify $commit:"$filter_subdir" 2>/dev/null
+			if ! git rev-parse -q --verify $commit:"$filter_subdir"
 			then
 				rm -f "$GIT_INDEX_FILE"
 			else