refactor<*>: rewrite all with AvaloniaUI

src/ViewModels/FastForwardWithoutCheckout.cs

@@ -0,0 +1,34 @@
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels {
+    public class FastForwardWithoutCheckout : Popup {
+        public Models.Branch Local {
+            get;
+            private set;
+        }
+
+        public Models.Branch To {
+            get;
+            private set;
+        }
+
+        public FastForwardWithoutCheckout(Repository repo, Models.Branch local, Models.Branch upstream) {
+            _repo = repo;
+            Local = local;
+            To = upstream;
+            View = new Views.FastForwardWithoutCheckout() { DataContext = this };
+        }
+
+        public override Task<bool> Sure() {
+            _repo.SetWatcherEnabled(false);
+            return Task.Run(() => {
+                SetProgressDescription("Fast-Forward ...");
+                new Commands.Fetch(_repo.FullPath, To.Remote, Local.Name, To.Name, SetProgressDescription).Exec();
+                CallUIThread(() => _repo.SetWatcherEnabled(true));
+                return true;
+            });
+        }
+
+        private Repository _repo = null;
+    }
+}