[jingai]

fatal: Not a git repository (or any of the parent directories): .git

Ah, it seems you didn't use git to fetch the sources originally, hence why you didn't have git installed. I'm assuming you downloaded the ZIP archive from the Releases tab. If you did, you can just download the new ZIP from there and unpack it over the old source (retaining your venv directory) and do all of the other steps besides "git pull origin master".