add INudge interface; Move tries to nudge things that are in the way as a good first option

OpenRA.Game/Traits/Activities/Move.cs

@@ -151,8 +151,19 @@ namespace OpenRA.Traits.Activities
 		}
 
 		bool hasWaited;
+		bool hasNudged;
 		int waitTicksRemaining;
 
+		void NudgeBlocker(Actor self, int2 nextCell)
+		{
+			var blocker = self.World.WorldActor.traits.Get<UnitInfluence>().GetUnitsAt(nextCell).FirstOrDefault();
+			if (blocker == null) return;
+
+			var nudge = blocker.traits.GetOrDefault<INudge>();
+			if (nudge != null)
+				nudge.OnNudge(blocker);
+		}
+
 		int2? PopPath( Actor self, Mobile mobile )
 		{
 			if( path.Count == 0 ) return null;
@@ -165,6 +176,12 @@ namespace OpenRA.Traits.Activities
 					return null;
 				}
 
+				if (!hasNudged)
+				{
+					NudgeBlocker(self, nextCell);
+					hasNudged = true;
+				}
+
 				if (!hasWaited)
 				{
 					var info = self.Info.Traits.Get<MobileInfo>();
@@ -187,6 +204,7 @@ namespace OpenRA.Traits.Activities
 
 				return null;
 			}
+			hasNudged = false;
 			hasWaited = false;
 			path.RemoveAt( path.Count - 1 );
 			return nextCell;

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -53,6 +53,7 @@ namespace OpenRA.Traits
 
 	public interface IDisable { bool Disabled { get; } }
 	public interface IExplodeModifier { bool ShouldExplode(Actor self); }
+	public interface INudge { bool OnNudge(Actor self); }
 
 	public interface IOccupySpace
 	{