Add update script (#248)

scripts/update.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+# Check for root
+if [ "$(id -u)" != "0" ]; then
+   echo "This script must be run as root" 1>&2
+   exit 1
+fi
+
+# Check for internet connection
+wget -q --spider http://google.com
+if [ $? -eq 0 ]; then
+    echo "Internet connection OK"
+else
+    echo "This script requires an Internet connection! Exiting"
+    exit 1
+fi
+
+echo "Stopping PhotonVision service"
+systemctl stop photonvision
+
+echo "Downloading and installing latest stable release of PhotonVision..."
+cd /opt/photonvision
+rm photonvision.jar
+curl -sk https://api.github.com/repos/photonvision/photonvision/releases/latest |
+    grep "browser_download_url.*jar" |
+    cut -d : -f 2,3 |
+    tr -d '"' |
+    wget -qi - -O photonvision.jar
+
+echo "Starting PhotonVision service"
+systemctl start photonvision
+
+echo "PhotonVision update succesful!"