Factor out GetServiceAsync

Author: jcansdale

src/GitHub.TeamFoundation.14/Services/VSGitExt.cs

@@ -99,10 +99,7 @@ async Task ContextChangedAsync()
 
         async Task<bool> TryInitialize()
         {
-            // GetService must be called on the Main thread.
-            await ThreadingHelper.SwitchToMainThreadAsync();
-
-            gitService = serviceProvider.GetService<IGitExt>();
+            gitService = await GetServiceAsync<IGitExt>();
             if (gitService != null)
             {
                 gitService.PropertyChanged += (s, e) =>
@@ -125,6 +122,13 @@ async Task<bool> TryInitialize()
             return false;
         }
 
+        async Task<T> GetServiceAsync<T>() where T : class
+        {
+            // GetService must be called from the Main thread.
+            await ThreadingHelper.SwitchToMainThreadAsync();
+            return serviceProvider.GetService<T>();
+        }
+
         void RefreshActiveRepositories()
         {
             try