Omit some expensive GameData members when cloning for BattleCalc. (#10467)

* Minimize battle calc data cloning.

* Clean up

* Improve comment.

* Address style comments.

Author: asvitkine

game-app/game-core/src/main/java/games/strategy/engine/data/GameData.java

@@ -107,7 +107,7 @@ public class GameData implements Serializable, GameState {
   @Getter private transient TechTracker techTracker = new TechTracker(this);
   private final IGameLoader loader = new TripleA();
   private History gameHistory = new History(this);
-  private final List<Tuple<IAttachment, List<Tuple<String, String>>>> attachmentOrderAndValues =
+  private List<Tuple<IAttachment, List<Tuple<String, String>>>> attachmentOrderAndValues =
       new ArrayList<>();
   private final Map<String, TerritoryEffect> territoryEffectList = new HashMap<>();
   private final BattleRecordsList battleRecordsList = new BattleRecordsList(this);
@@ -401,6 +401,11 @@ public List<Tuple<IAttachment, List<Tuple<String, String>>>> getAttachmentOrderA
     return attachmentOrderAndValues;
   }
 
+  public void setAttachmentOrderAndValues(
+      List<Tuple<IAttachment, List<Tuple<String, String>>>> values) {
+    attachmentOrderAndValues = values;
+  }
+
   /**
    * Returns all relationshipTypes that are valid in this game, default there is the NullRelation
    * (relation with the Null player / Neutral) and the SelfRelation (Relation with yourself) all

game-app/game-core/src/main/java/games/strategy/engine/framework/GameDataManager.java

@@ -207,18 +207,27 @@ public static void saveGame(
   public static void saveGameUncompressed(
       final OutputStream sink,
       final GameData data,
-      final boolean saveDelegateInfo,
+      final boolean saveDelegateInfoHistoryAndAttachmentsOrder,
       final Version engineVersion)
       throws IOException {
     // write to temporary file first in case of error
     try (ObjectOutputStream outStream = new ObjectOutputStream(sink)) {
       outStream.writeObject(engineVersion);
       data.acquireReadLock();
       try {
-        outStream.writeObject(data);
-        if (saveDelegateInfo) {
+        if (saveDelegateInfoHistoryAndAttachmentsOrder) {
+          outStream.writeObject(data);
           writeDelegates(data, outStream);
         } else {
+          // TODO: Attachment order data is only used for XML export and takes up lots of memory.
+          // Could we remove it and just get the info again from the XML when exporting?
+          final var attachments = data.getAttachmentOrderAndValues();
+          final var history = data.getHistory();
+          data.setAttachmentOrderAndValues(null);
+          data.resetHistory();
+          outStream.writeObject(data);
+          data.setAttachmentOrderAndValues(attachments);
+          data.setHistory(history);
           outStream.writeObject(DELEGATE_LIST_END);
         }
       } finally {