Micro Bit setup "command failed: fatal: ambiguous argument 'Head' : unknown revision or path not in working tree."

I have had my Micro Bit for 36 hours and have been using https://www.instructables.com/id/BBC-Microbit-C-Off-line-Setup/ to setup my machine. I've solved a number of other errors but having spent a continuous 20 hours on the title issue..

There are many such problems on the web but a minority referred to the Micro Bit and those that did seem to be platform specific or in specific machine states. Nobody seems to know exactly what causes it, but offer unusable (to me) workarounds.

Many thanks for your time,