More echo "$user_message" fixes.

Here are fixes to more uses of 'echo "$msg"' where $msg could contain
backslashed sequence.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-am.sh

@@ -18,7 +18,7 @@ stop_here () {
 
 stop_here_user_resolve () {
     if [ -n "$resolvemsg" ]; then
-	    echo "$resolvemsg"
+	    printf '%s\n' "$resolvemsg"
 	    stop_here $1
     fi
     cmdline=$(basename $0)
@@ -146,7 +146,7 @@ do
 	git_apply_opt="$git_apply_opt $1"; shift ;;
 
 	--resolvemsg=*)
-	resolvemsg=$(echo "$1" | sed -e "s/^--resolvemsg=//"); shift ;;
+	resolvemsg=${1#--resolvemsg=}; shift ;;
 
 	--)
 	shift; break ;;