Fix MCV deploy erasing Iron Curtain history.

OpenRA.Mods.Cnc/Traits/TransferTimedExternalConditionOnTransform.cs

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+#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.Linq;
+using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Cnc.Traits
+{
+	[Desc("A special case trait that re-grants a timed external condition when this actor transforms.",
+		"This trait does not work with permanently granted external conditions.",
+		"This trait changes the external condition source, so cannot be used for conditions that may later be revoked")]
+	public class TransferTimedExternalConditionOnTransformInfo : ITraitInfo, Requires<TransformsInfo>
+	{
+		[FieldLoader.Require]
+		[Desc("External condition to transfer")]
+		public readonly string Condition = null;
+
+		public object Create(ActorInitializer init) { return new TransferTimedExternalConditionOnTransform(this); }
+	}
+
+	public class TransferTimedExternalConditionOnTransform : IConditionTimerWatcher, INotifyTransform
+	{
+		readonly TransferTimedExternalConditionOnTransformInfo info;
+		int duration = 0;
+		int remaining = 0;
+
+		public TransferTimedExternalConditionOnTransform(TransferTimedExternalConditionOnTransformInfo info)
+		{
+			this.info = info;
+		}
+
+		void INotifyTransform.BeforeTransform(Actor self) { }
+		void INotifyTransform.OnTransform(Actor self) { }
+
+		void INotifyTransform.AfterTransform(Actor toActor)
+		{
+			if (remaining <= 0)
+				return;
+
+			var external = toActor.TraitsImplementing<ExternalCondition>()
+				.FirstOrDefault(t => t.Info.Condition == info.Condition && t.CanGrantCondition(toActor, this));
+
+			if (external != null)
+				external.GrantCondition(toActor, this, duration, remaining);
+		}
+
+		void IConditionTimerWatcher.Update(int duration, int remaining)
+		{
+			this.duration = duration;
+			this.remaining = remaining;
+		}
+
+		string IConditionTimerWatcher.Condition { get { return info.Condition; } }
+	}
+}