Defer updates of deactivated PR details.

When a repository change is detected by a non-active `PullRequestDetailViewModel`, set a flag to refresh the view model when it becomes active again.

Author: grokys

src/GitHub.App/ViewModels/GitHubPane/PullRequestDetailViewModel.cs

@@ -4,6 +4,7 @@
 using System.IO;
 using System.Linq;
 using System.Reactive;
+using System.Reactive.Disposables;
 using System.Reactive.Linq;
 using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
@@ -46,6 +47,8 @@ public sealed class PullRequestDetailViewModel : PanePageViewModelBase, IPullReq
         bool isCheckedOut;
         bool isFromFork;
         bool isInCheckout;
+        bool active;
+        bool refreshOnActivate;
         Uri webUrl;
 
         /// <summary>
@@ -482,6 +485,21 @@ public string GetLocalFilePath(IPullRequestFileNode file)
             return Path.Combine(LocalRepository.LocalPath, file.DirectoryPath, file.FileName);
         }
 
+        /// <inheritdoc/>
+        public override void Activated()
+        {
+            active = true;
+
+            if (refreshOnActivate)
+            {
+                Refresh().Forget();
+                refreshOnActivate = false;
+            }
+        }
+
+        /// <inheritdoc/>
+        public override void Deactivated() => active = false;
+
         /// <inheritdoc/>
         protected override void Dispose(bool disposing)
         {
@@ -493,7 +511,17 @@ protected override void Dispose(bool disposing)
             }
         }
 
-        void ActiveRepositoriesChanged() => Refresh().Forget();
+        void ActiveRepositoriesChanged()
+        {
+            if (active)
+            {
+                Refresh().Forget();
+            }
+            else
+            {
+                refreshOnActivate = true;
+            }
+        }
 
         void SubscribeOperationError(ReactiveCommand<Unit> command)
         {