Don't show Sync UI when there are no submodule changes

Hide the icon and counter as well as the Sync button.

Author: jcansdale

src/GitHub.VisualStudio/Views/GitHubPane/PullRequestDetailView.xaml

@@ -184,8 +184,10 @@
                                              ToolTipService.ShowOnDisabled="True"
                                              VerticalAlignment="Center"/>
                         <!-- Sync submodules -->
-                        <ui:OcticonImage Icon="package"/>
-                        <TextBlock  Margin="4 0 0 0" Text="{Binding UpdateState.SubmodulesToSync}" VerticalAlignment="Center"/>
+                        <ui:OcticonImage Icon="package"
+                            Visibility="{Binding UpdateState.SyncSubmodulesEnabled, FallbackValue=Collapsed, Converter={ui:BooleanToVisibilityConverter}}" />
+                        <TextBlock  Margin="4 0 0 0" Text="{Binding UpdateState.SubmodulesToSync}" VerticalAlignment="Center"
+                            Visibility="{Binding UpdateState.SyncSubmodulesEnabled, FallbackValue=Collapsed, Converter={ui:BooleanToVisibilityConverter}}" />
                         <ui:GitHubActionLink Content="Sync"
                             Command="{Binding SyncSubmodules}"
                             Margin="4 0"