setup: add support for performing factory reset

Now that we have dialog on target we can add a user-friendly factory
reset dialog.  The new `yorn` script handles any form of yes-or-no
question, with or without dialog, to call a command.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/rootfs/bin/setup

@@ -61,6 +61,7 @@ menu:system:System:System Settings
 	exec:_Disable service:edit:initctl disable ~Enter name of service (filename) to disable:~
 	nop
 	exec:_Change Operating Mode::chom
+	exec:_Factory Reset::yorn "Reboot and factory reset device, are you sure?" factory -y
 	nop
 	exit:_Main menu..
 

board/common/rootfs/bin/yorn

@@ -0,0 +1,55 @@
+#!/bin/sh
+#set -x
+
+usage()
+{
+    cat <<EOF
+usage:
+  yorn [-h] ["Do you want to run command?" command]
+
+options:
+  -h            Show this help text
+  -p            Show plain output, no bells or whistles
+
+Displays the yes-or-no question and runs command on yes.
+EOF
+}
+
+if [ -z "$1" ]; then
+    usage
+    exit 1
+fi
+
+case $1 in
+    -h)
+	usage
+	exit 0
+	;;
+    -p)
+	plain=1
+	shift
+	;;
+    *)
+	;;
+esac
+
+question=$1
+shift
+command=$*
+if [ -z "$command" ]; then
+    usage
+    exit 1
+fi
+
+if [ -z "$plain" ]; then
+    if dialog --erase-on-exit --colors --defaultno --yesno "\Zb$question\ZB" 0 0; then
+	yorn=y
+    fi
+else
+    # shellcheck disable=SC2162,SC3045
+    read -n 1 -p "$question (y/N): " yorn
+fi
+
+if [ "$yorn" = "y" ] || [ "$yorn" = "Y" ]; then
+    $command
+fi