ux: makes BranchSelector looks like normal ComboBox

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

Author: love-linger

src/Views/BranchSelector.axaml

@@ -147,6 +147,15 @@
           <Setter Property="Background" Value="{DynamicResource ComboBoxBackgroundUnfocused}" />
         </Style>
       </Style>
+
+      <Style Selector="^:disabled">
+        <Setter Property="Opacity" Value="0.6"/>
+        
+        <Style Selector="^ /template/ Border#PART_Background">
+          <Setter Property="Background" Value="Transparent" />
+          <Setter Property="BorderBrush" Value="{DynamicResource Brush.Border2}"/>
+        </Style>
+      </Style>
     </Style>
   </UserControl.Styles>
 </UserControl>