Convert to use quiet option when available

A minor fix that eliminates usage of "2>/dev/null" when --quiet or
-q has already been implemented.

Signed-off-by: Dan Loewenherz <daniel.loewenherz@yale.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-merge-resolve.sh

@@ -37,10 +37,10 @@ then
 	exit 2
 fi
 
-git update-index --refresh 2>/dev/null
+git update-index -q --refresh
 git read-tree -u -m --aggressive $bases $head $remotes || exit 2
 echo "Trying simple merge."
-if result_tree=$(git write-tree  2>/dev/null)
+if result_tree=$(git write-tree 2>/dev/null)
 then
 	exit 0
 else