feature: allow using Amend while rebasing (#773)

Author: love-linger

src/Views/WorkingCopy.axaml

@@ -239,7 +239,6 @@
                   Margin="8,0,0,0"
                   HorizontalAlignment="Left"
                   IsChecked="{Binding UseAmend, Mode=TwoWay}"
-                  IsVisible="{Binding InProgressContext, Converter={x:Static ObjectConverters.IsNull}}"
                   Content="{DynamicResource Text.WorkingCopy.Amend}"/>
 
         <v:LoadingIcon Grid.Column="5" Width="18" Height="18" IsVisible="{Binding IsCommitting}"/>