gh-91167: Fix cloned turtle pen not clearing completely

When calling clear() on a cloned turtle, it incorrectly cleared the source
turtle's drawings instead of its own. Fix by reinitializing the clone's
currentLine and items to track only its own drawing state.

Author: yukarikaname

Lib/test/test_turtle.py

@@ -671,6 +671,21 @@ def test_dot_signature(self):
         self.assertRaises(turtle.TurtleGraphicsError, self.turtle.dot, 0, (0, 257, 0))
         self.assertRaises(turtle.TurtleGraphicsError, self.turtle.dot, 0, 0, 257, 0)
 
+    def test_clone_clear_does_not_delete_source_items(self):
+        screen = self.turtle.screen
+        screen._delete.reset_mock()
+        screen._createline.side_effect = lambda: object()
+
+        self.turtle.circle(20)
+        clone = self.turtle.clone()
+        source_items = set(self.turtle.items)
+
+        clone.forward(50)
+        clone.clear()
+
+        deleted_items = {call.args[0] for call in screen._delete.call_args_list}
+        self.assertFalse(source_items & deleted_items)
+
 class TestModuleLevel(unittest.TestCase):
     def test_all_signatures(self):
         import inspect

Lib/turtle.py

@@ -2879,6 +2879,8 @@ def clone(self):
             q.turtle._item = [screen._createpoly() for item in
                               screen._shapes[self.turtle.shapeIndex]._data]
         q.currentLineItem = screen._createline()
+        q.currentLine = [q._position] if q._drawing else []
+        q.items = [q.currentLineItem]
         q._update()
         return q