Added Gates

FIXUP: account for full gate footprint when updating neighbours.

FIXUP: gate-wall connection adjacency yaml.

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -284,6 +284,13 @@ namespace OpenRA.Traits
 		bool CanEnterTargetNow(Actor self, Target target);
 	}
 
+	[RequireExplicitImplementation]
+	public interface ITemporaryBlocker
+	{
+		bool CanRemoveBlockage(Actor self, Actor blocking);
+		bool IsBlocking(Actor self, CPos cell);
+	}
+
 	public interface INotifyBlockingMove { void OnNotifyBlockingMove(Actor self, Actor blocking); }
 
 	public interface IFacing

OpenRA.Game/WorldUtils.cs

@@ -37,6 +37,23 @@ namespace OpenRA
 				a => (a.CenterPosition - origin).HorizontalLengthSquared <= r.LengthSquared);
 		}
 
+		public static bool ContainsTemporaryBlocker(this World world, CPos cell, Actor ignoreActor = null)
+		{
+			var temporaryBlockers = world.ActorMap.GetActorsAt(cell);
+			foreach (var temporaryBlocker in temporaryBlockers)
+			{
+				if (temporaryBlocker == ignoreActor)
+					continue;
+
+				var temporaryBlockerTraits = temporaryBlocker.TraitsImplementing<ITemporaryBlocker>();
+				foreach (var temporaryBlockerTrait in temporaryBlockerTraits)
+					if (temporaryBlockerTrait.IsBlocking(temporaryBlocker, cell))
+						return true;
+			}
+
+			return false;
+		}
+
 		public static void DoTimed<T>(this IEnumerable<T> e, Action<T> a, string text)
 		{
 			// PERF: This is a hot path and must run with minimal added overhead.