style<Welcome>: replace system message dialog with a custom one

src/Views/ConfirmDialog.xaml.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Windows;
+
+namespace SourceGit.Views {
+
+    /// <summary>
+    ///     通用的确认弹出框
+    /// </summary>
+    public partial class ConfirmDialog : Controls.Window {
+        private Action cbOK;
+        private Action cbCancel;
+
+        public ConfirmDialog(string title, string message, Action onOk, Action onCancel = null) {
+            InitializeComponent();
+            
+            txtTitle.Text = title;
+            txtMessage.Text = message;
+
+            cbOK = onOk;
+            cbCancel = onCancel;
+        }
+
+        private void OnSure(object sender, RoutedEventArgs e) {
+            cbOK?.Invoke();
+            Close();
+        }
+
+        private void OnQuit(object sender, RoutedEventArgs e) {
+            cbCancel?.Invoke();
+            Close();
+        }
+    }
+}