refactor<*>: rewrite all with AvaloniaUI

src/ViewModels/Squash.cs

@@ -0,0 +1,43 @@
+using System.ComponentModel.DataAnnotations;
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels {
+    public class Squash : Popup {
+        public Models.Commit Head {
+            get;
+            private set;
+        }
+
+        public Models.Commit Parent {
+            get;
+            private set;
+        }
+
+        [Required(ErrorMessage = "Commit message is required!!!")]
+        public string Message {
+            get => _message;
+            set => SetProperty(ref _message, value, true);
+        }
+
+        public Squash(Repository repo, Models.Commit head, Models.Commit parent) {
+            _repo = repo;
+            _message = parent.FullMessage;
+            Head = head;
+            Parent = parent;
+            View = new Views.Squash() { DataContext = this };
+        }
+
+        public override Task<bool> Sure() {
+            _repo.SetWatcherEnabled(false);
+            return Task.Run(() => {
+                var succ = new Commands.Reset(_repo.FullPath, Parent.SHA, "--soft").Exec();
+                if (succ) succ = new Commands.Commit(_repo.FullPath, _message, true).Exec();
+                CallUIThread(() => _repo.SetWatcherEnabled(true));
+                return succ;
+            });
+        }
+
+        private Repository _repo = null;
+        private string _message = string.Empty;
+    }
+}