Put simply the steps to migrate source code off TFVC onto Git whilst retaining all history are as follows:
1. Create a new local directory on your machine to clone the existing TFVC source code into
2. Download the git-tfs tfs/git bridging tool https://github.com/git-tfs/git-tfs/releases
3. git-tfs clone http://tfs:8080/tfs/isd “$/
4. git remote add origin http://tfs:8080/tfs/ISD/_git/
5. git push -u origin –all (if you get authentication errors go to Start > Credential Manager and remove tfs entries.