repetition: Revert detect 3-fold repetition during searching follow Stockfish

And change to tscp181c-like

Because:

Stockfish-like Vs tscp181c-like
played 9000

12 men without fly
11.45% : 86.55% : 1.99%
12.93% : 86.12% : 0.94%
= 48.79% : 49.74%

9 men with fly
26.16% : 37.62% : 36.21%
28.59% : 38.09% : 33.31%
= 32.13% : 33.11%

src/search.cpp

@@ -211,7 +211,7 @@ Value search(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth ori
         }
     }
 
-#ifdef THREEFOLD_REPETITION
+#ifdef THREEFOLD_REPETITION_TEST
     // Check if we have an upcoming move which draws by repetition, or
     // if the opponent had an alternative move earlier to this position.
     if (/* alpha < VALUE_DRAW && */
@@ -329,6 +329,16 @@ Value search(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth ori
         return bestValue;
     }
 
+#ifdef THREEFOLD_REPETITION
+    // if this isn't the root of the search tree (where we have
+    // to pick a move and can't simply return VALUE_DRAW) then check to
+    // see if the position is a repeat. if so, we can assume that
+    // this line is a draw and return VALUE_DRAW.
+    if (depth != originDepth && pos->has_repeated(ss)) {
+        return VALUE_DRAW;
+    }
+#endif // THREEFOLD_REPETITION
+
     MovePicker mp(*pos);
     Move nextMove = mp.next_move();
     const int moveCount = mp.move_count();