At least as of last year, this feature isn't implemented
As of this writing, Visual Studio 2013 does not have support for ssh-based remotes. If you have a Git remote that uses SSH and you try to perform a network operation in Visual Studio, you’ll get the message “This transport isn’t implemented. Sorry.” (This message comes from the libgit2 library.) I don’t have a timeline for when support for SSH remotes might be implemented in Visual Studio.