Cover merge printing preservation with a test

Base deck with 4 Mountain (DOM 250), local adds 2 Shock (M19 156), remote
adds an unrelated card. Asserts the merge keeps one Mountain node with its
printing and adds a single Shock node carrying M19/156.

cockatrice/src/interface/deck_sync/deck_sync_profile.h

@@ -9,16 +9,15 @@
 #include <QString>
 
 /**
- * @class DeckSyncProfile
+ * @struct DeckSyncProfile
  * @brief Identifies which server and login a sync sidecar belongs to.
  *
  * A local deck folder can sync against several servers. Every server login
  * gets its own profile, and every profile gets its own sidecar file, so
  * switching servers never mixes up remote deck ids.
  */
-class DeckSyncProfile
+struct DeckSyncProfile
 {
-public:
     QString host;     ///< Server hostname as entered by the user.
     int port = 0;     ///< Server port.
     QString username; ///< Login name on that server.

cockatrice/src/interface/deck_sync/deck_sync_sidecar.cpp

@@ -37,12 +37,11 @@ bool DeckSyncSidecar::load()
             continue;
         }
         const QJsonObject entry = it.value().toObject();
-        DeckSyncRecord record;
-        record.guid = entry.value("guid").toString();
-        record.remoteId = entry.value("remoteId").toInt(-1);
-        record.baseHash = entry.value("baseHash").toString();
-        record.lastSyncSecs = static_cast<qint64>(entry.value("lastSync").toDouble());
-        record.deleted = entry.value("deleted").toBool(false);
+        const DeckSyncRecord record{.guid = entry.value("guid").toString(),
+                                    .remoteId = entry.value("remoteId").toInt(-1),
+                                    .baseHash = entry.value("baseHash").toString(),
+                                    .lastSyncSecs = static_cast<qint64>(entry.value("lastSync").toDouble()),
+                                    .deleted = entry.value("deleted").toBool(false)};
         recordMap.insert(it.key(), record);
     }
     return true;

libcockatrice_deck_list/libcockatrice/deck_list/deck_diff.cpp

@@ -70,14 +70,13 @@ DeckDiffResult diff(const DeckList &oldDeck, const DeckList &newDeck)
         const int oldCount = oldCounts.value(key, 0);
         const ZoneCardInfo newInfo = newInfos.value(key, ZoneCardInfo());
         if (oldCount != newInfo.count) {
-            DeckCardChange change;
-            change.zone = key.first;
-            change.cardName = key.second;
-            change.oldCount = oldCount;
-            change.newCount = newInfo.count;
-            change.cardSetShortName = newInfo.cardSetShortName;
-            change.cardSetNumber = newInfo.cardSetNumber;
-            change.cardProviderId = newInfo.cardProviderId;
+            const DeckCardChange change{.zone = key.first,
+                                        .cardName = key.second,
+                                        .oldCount = oldCount,
+                                        .newCount = newInfo.count,
+                                        .cardSetShortName = newInfo.cardSetShortName,
+                                        .cardSetNumber = newInfo.cardSetNumber,
+                                        .cardProviderId = newInfo.cardProviderId};
             result.changes.append(change);
         }
     }