Auto-load GitHubPackage when there is an active repository

Make GitHubPackage auto-load on backgroundLoad thread.

Author: jcansdale

src/GitHub.VisualStudio/GitHubPackage.cs

@@ -28,8 +28,8 @@ namespace GitHub.VisualStudio
     [InstalledProductRegistration("#110", "#112", System.AssemblyVersionInformation.Version, IconResourceID = 400)]
     [Guid(Guids.guidGitHubPkgString)]
     [ProvideMenuResource("Menus.ctmenu", 1)]
-    // this is the Git service GUID, so we load whenever it loads
-    [ProvideAutoLoad(Guids.GitSccProviderId)]
+    // Only initialize when we're in the context of a Git repository.
+    [ProvideAutoLoad(Guids.UIContext_Git, PackageAutoLoadFlags.BackgroundLoad)]
     [ProvideToolWindow(typeof(GitHubPane), Orientation = ToolWindowOrientation.Right, Style = VsDockStyle.Tabbed, Window = EnvDTE.Constants.vsWindowKindSolutionExplorer)]
     [ProvideOptionPage(typeof(OptionsPage), "GitHub for Visual Studio", "General", 0, 0, supportsAutomation: true)]
     public class GitHubPackage : AsyncPackage