Update detector, untested.

src/main/java/net/runelite/deob/updater/UpdateDetector.java

@@ -0,0 +1,57 @@
+package net.runelite.deob.updater;
+
+import com.google.gson.Gson;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class UpdateDetector
+{
+	public static void main(String[] args) throws IOException
+	{
+		if (args.length < 1)
+			System.exit(-1);
+
+		File saveFile = new File(args[0]);
+		if (!saveFile.exists())
+		{
+			GameConfig config = new GameConfig();
+			config.fetch();
+			save(config, saveFile);
+			return;
+		}
+
+		GameConfig saved = load(saveFile);
+
+		GameConfig current = new GameConfig();
+		current.fetch();
+
+		GameConfigUpdateDetector gcud = new GameConfigUpdateDetector(saved, current);
+		boolean updated = gcud.hasUpdated();
+
+		System.exit(updated ? 0 : -1);
+	}
+
+
+	public static void save(GameConfig conf, File f) throws IOException
+	{
+		try (FileOutputStream fout = new FileOutputStream(f))
+		{
+			Gson g = new Gson();
+			String s = g.toJson(conf);
+			fout.write(s.getBytes());
+		}
+	}
+
+	public static GameConfig load(File f) throws IOException
+	{
+		try (FileInputStream fin = new FileInputStream(f))
+		{
+			Gson g = new Gson();
+			return g.fromJson(new InputStreamReader(fin), GameConfig.class);
+		}
+	}
+
+}