Here's how to disable the package that is responsible for loading the Git source control support in Visual Studio. Use at your own risk!

• Create a file called devenv.pkgundef and place it next to devenv.exe in you Visual Studio's Common7\IDE (you'll need elevation for this)
• Add the following entries to the file:

[$RootKey$\Packages\{7fe30a77-37f9-4cf2-83dd-96b207028e1b}]
[$RootKey$\SourceControlProviders\{11b8e6d7-c08b-4385-b321-321078cdd1f8}]

• Close VS if open, open a Developer command prompt, and type devenv /updateconfiguration