VSPackage: How to download files from Git repository?

I'm wrote the Diff All Files Visual Studio extension, which pulls files down from TFS source control in order to bulk compare your changes more quickly.  I'm now adding Git functionality to it, but cannot seem to locate the class that I should use in order to pull files from the Git repository.  In TFS I used:

var versionControl = this.GetService<Microsoft.TeamFoundation.VersionControl.Client.VersionControlServer>();

However this just returns null when using a Git repository.  What service should I be retrieving in order to download files from the Git repository?  If anybody has an example of getting the Git repo service and downloading a file from it that would be awesome. This is for Visual Studio 2013.  Thanks.

- Dan - "Can't never could do anything"