Refreshes apps by installing provisioning profiles when possible

Assuming the certificate used to originally sign an app is still valid, we can refresh an app simply by installing new provisioning profiles. However, if the signing certificate is no longer valid, we fall back to the old method of resigning + reinstalling.

AltStore/AppDelegate.swift

@@ -64,6 +64,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
     var window: UIWindow?
     
     private var runningApplications: Set<String>?
+    private var backgroundRefreshContext: NSManagedObjectContext? // Keep context alive until finished refreshing.
 
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool
     {
@@ -209,6 +210,8 @@ extension AppDelegate
                 }
                 
                 taskCompletionHandler()
+                
+                self.backgroundRefreshContext = nil
             }
             
             if let error = taskResult.error
@@ -339,7 +342,6 @@ private extension AppDelegate
             dispatchGroup.enter()
             
             DatabaseManager.shared.persistentContainer.performBackgroundTask { (context) in
-                
                 let installedApps = InstalledApp.fetchAppsForBackgroundRefresh(in: context)
                 guard !installedApps.isEmpty else {
                     serversResult = .success(())
@@ -351,6 +353,7 @@ private extension AppDelegate
                 }
                 
                 self.runningApplications = []
+                self.backgroundRefreshContext = context
                 
                 let identifiers = installedApps.compactMap { $0.bundleIdentifier }
                 print("Apps to refresh:", identifiers)
@@ -398,7 +401,7 @@ private extension AppDelegate
                             
                             // Also since AltServer has already received the app, it can finish installing even if we're no longer running in background.
                             
-                            if let error = group.error
+                            if let error = group.context.error
                             {
                                 self.scheduleFinishedRefreshingNotification(for: .failure(error), identifier: identifier)
                             }
@@ -410,8 +413,8 @@ private extension AppDelegate
                                 self.scheduleFinishedRefreshingNotification(for: .success(results), identifier: identifier)
                             }
                         }
-                        group.completionHandler = { (result) in
-                            completionHandler(result)
+                        group.completionHandler = { (results) in
+                            completionHandler(.success(results))
                         }
                     }
                 }