[C21] Implemented Battlemage's Braces

Mage/src/main/java/mage/abilities/effects/common/CopyStackAbilityEffect.java

@@ -0,0 +1,39 @@
+package mage.abilities.effects.common;
+
+import mage.abilities.Ability;
+import mage.abilities.effects.OneShotEffect;
+import mage.constants.Outcome;
+import mage.game.Game;
+import mage.game.stack.StackAbility;
+import mage.players.Player;
+
+/**
+ * @author TheElk801
+ */
+public class CopyStackAbilityEffect extends OneShotEffect {
+
+    public CopyStackAbilityEffect() {
+        super(Outcome.Copy);
+        staticText = "copy that ability. You may choose new targets for the copy";
+    }
+
+    private CopyStackAbilityEffect(final CopyStackAbilityEffect effect) {
+        super(effect);
+    }
+
+    @Override
+    public CopyStackAbilityEffect copy() {
+        return new CopyStackAbilityEffect(this);
+    }
+
+    @Override
+    public boolean apply(Game game, Ability source) {
+        Player controller = game.getPlayer(source.getControllerId());
+        StackAbility ability = (StackAbility) getValue("stackAbility");
+        if (controller == null || ability == null) {
+            return false;
+        }
+        ability.createCopyOnStack(game, source, source.getControllerId(), true);
+        return true;
+    }
+}