Argh!! Another very unhelpful error message:

What am I supposed to do with that? Today I found out what. Run the command again with –d for debug.

And there is the message that should be have been with the error code:

fatal: Unable to create ‘C:/Code/Main/.git\tfs\default\index.lock’: File exists. If no other git process is currently running, this probably means a git process crashed in this repository earlier. Make sure no other git process is running and remove the file manually to continue.

I can work with that. There were no other git processes running, but the file .git\tfs\default\index.lock did exist. Deleting that we get further, this time with a very helpful error message:

Run the command: git tfs cleanup-workspaces

Looks good. Run the pull again and we are back in business.