match the exact ordering of the source code

src/push_solve.rs

@@ -301,11 +301,15 @@ pub fn push_solve(contacts:&Vec<Contact>,point:Planar64Vec3)->Option<Planar64Vec
 			return Some(ray.origin);
 		}
 
-		//edit the indices
-		if conts.len()==4{
-			conts.pop();
-		}
+		//push_front
+		if conts.len()==conts.capacity(){
+			//this is a dead case, new_conts never has more than 3 elements
+			conts.rotate_right(1);
+			conts[0]=next_cont;
+		}else{
 			conts.push(next_cont);
+			conts.rotate_right(1);
+		}
 
 		let meet_point=ray.extrapolate(next_t);
 		match get_best_push_ray_and_conts(meet_point,conts){