Add beta warning to legacy update path

OpenRA.Mods.Common/OpenRA.Mods.Common.csproj

@@ -606,6 +606,7 @@
     <Compile Include="UpdateRules\Rules\SplitGateFromBuilding.cs" />
     <Compile Include="UpdateRules\Rules\RenameBurstDelay.cs" />
     <Compile Include="UpdateRules\Rules\WarnAboutInfiltrateForTypes.cs" />
+    <Compile Include="UpdateRules\Rules\LegacyBetaWarning.cs" />
     <Compile Include="UtilityCommands\CheckYaml.cs" />
     <Compile Include="UtilityCommands\ConvertPngToShpCommand.cs" />
     <Compile Include="UtilityCommands\ConvertSpriteToPngCommand.cs" />

OpenRA.Mods.Common/UpdateRules/Rules/LegacyBetaWarning.cs

@@ -0,0 +1,45 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace OpenRA.Mods.Common.UpdateRules.Rules
+{
+	public class LegacyBetaWarning : UpdateRule
+	{
+		public override string Name { get { return "Update path from 20171014 to 20180307 is in beta state"; } }
+		public override string Description
+		{
+			get
+			{
+				return "Due to time constraints and the legacy status of the included rules,\n" +
+					"the update path to 20180307 is considered a beta path.\n" +
+					"If you encounter any issues, please report them on GitHub or our IRC channel.";
+			}
+		}
+
+		bool displayed;
+
+		public override IEnumerable<string> AfterUpdate(ModData modData)
+		{
+			var message = "Due to time constraints and the legacy status of the included rules,\n" +
+					"the update path to 20180307 is considered a beta path.\n" +
+					"If you encounter any issues, please report them on GitHub or our IRC channel.";
+
+			if (!displayed)
+				yield return message;
+
+			displayed = true;
+		}
+	}
+}

OpenRA.Mods.Common/UpdateRules/UpdatePath.cs

@@ -36,6 +36,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 		{
 			new UpdatePath("release-20171014", "release-20180218", new UpdateRule[]
 			{
+				new LegacyBetaWarning(),
 				new RemoveMobileOnRails(),
 				new AircraftCanHoverGeneralization(),
 				new AddNukeLaunchAnimation(),