[AltStore] Adds redesigned AppViewController to view/download AltStore apps

AltStore/Model/MergePolicy.swift

@@ -0,0 +1,39 @@
+//
+//  MergePolicy.swift
+//  AltStore
+//
+//  Created by Riley Testut on 7/23/19.
+//  Copyright © 2019 Riley Testut. All rights reserved.
+//
+
+import CoreData
+
+import Roxas
+
+open class MergePolicy: RSTRelationshipPreservingMergePolicy
+{
+    open override func resolve(constraintConflicts conflicts: [NSConstraintConflict]) throws
+    {
+        guard conflicts.allSatisfy({ $0.databaseObject != nil }) else {
+            assertionFailure("MergePolicy is only intended to work with database-level conflicts.")
+            return try super.resolve(constraintConflicts: conflicts)            
+        }
+        
+        for conflict in conflicts
+        {
+            switch conflict.databaseObject
+            {
+            case let databaseObject as App:
+                // Delete previous permissions
+                for permission in databaseObject.permissions
+                {
+                    permission.managedObjectContext?.delete(permission)
+                }
+                
+            default: break
+            }
+        }
+        
+        try super.resolve(constraintConflicts: conflicts)
+    }
+}