In LightSwitch:
What is the role of the _Pvt_Extensions directory?
Why is it generally recommended that this directory not be included in the source control? Do you need content? Is it pulled out from somewhere (where?) If it is not found?
Why does Microsoft recommend including this directory in the source control for Team builders (see How to create LightSwitch projects with the Visual Studio TFS 2012 Build team )?
When you click the button to use the extension, the files that LightSwitch requires for this extension are copied to this folder.
Not sure about source control recommendations.