base-files: firstboot: only ask for confirmation on TTY

Also allow '-y' to force the reset.

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36133 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/base-files/files/sbin/firstboot

@@ -21,11 +21,13 @@ if [ "${0##*/}" = "firstboot" ]; then
     if [ "$1" = "switch2jffs" ]; then
 	boot_run_hook switch2jffs
     else
+	if [ -t 0 ] && [ "$1" != "-y" ]; then
 		local input
 
 		echo -n "firstboot will erase all settings and remove any installed packages. Are you sure? [N/y]"
 		read input
 		[ "$input" = "y" ] || [ "$input" = "Y" ] || return 0
+	fi
 
 	if [ -n "$jffs" ]; then
 	    reset_has_fo=true