Rework source fetching

Drop vendored copy of licensing module

Use git fetch-git reset to origin instead of git pull. Git pull may not work if the repo is in an unclean state. Resetting to origin should fix that.

Use heads[0] instead of heads.master to work with repo who use main or other branches as default. See Github move: https://github.blog/2020-07-27-highlights-from-git-2-28/