refactor: standalone commit message editor (#2096)

- Clicking `OK` button will apply the modified message and exit with code `0`
- Clicking `CANCEL` or pressing `ESC` will not apply the modified message and exit with code `-1`
- Clicking the window caption button `X` will not apply the modified message and exit with code `0`

Signed-off-by: leo <longshuang@msn.cn>

src/Views/CommitMessageEditor.axaml

@@ -37,12 +37,20 @@
 
     <StackPanel Grid.Row="1" Orientation="Vertical" Margin="8">
       <v:CommitMessageToolBox x:Name="Editor" Height="400"/>
-      <Button Classes="flat primary"
-              Width="80"
-              Margin="0,8,0,4"
-              Content="{DynamicResource Text.Sure}"
-              Click="SaveAndClose"
-              HorizontalAlignment="Center"/>
+
+      <StackPanel Margin="0,8,0,4" Orientation="Horizontal" HorizontalAlignment="Center" Spacing="8">
+        <Button Classes="flat primary"
+                Width="80"
+                Content="{DynamicResource Text.Sure}"
+                Click="SaveAndClose"
+                HorizontalAlignment="Center"/>
+        <Button Classes="flat"
+                Width="80"
+                Content="{DynamicResource Text.Cancel}"
+                Click="CancelAndClose"
+                HotKey="Escape"
+                HorizontalAlignment="Center"/>
+      </StackPanel>
     </StackPanel>
   </Grid>
 </v:ChromelessWindow>

src/Views/CommitMessageEditor.axaml.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Text.Json;
+
 using Avalonia.Interactivity;
 
 namespace SourceGit.Views
@@ -15,7 +16,6 @@ namespace SourceGit.Views
 
         public CommitMessageEditor()
         {
-            CloseOnESC = true;
             InitializeComponent();
         }
 
@@ -67,12 +67,17 @@ namespace SourceGit.Views
         private void SaveAndClose(object _1, RoutedEventArgs _2)
         {
             _onSave?.Invoke(Editor.CommitMessage);
-            _exitCode = 0;
+            Close();
+        }
+
+        private void CancelAndClose(object _1, RoutedEventArgs _2)
+        {
+            _exitCode = -1;
             Close();
         }
 
         private Action<string> _onSave = null;
         private bool _shouldExitApp = true;
-        private int _exitCode = -1;
+        private int _exitCode = 0;
     }
 }