Magit - A Git Porcelain inside Emacs - this is probably
the best git tool to quickly get work done if you are already married to the
git add before commit -
Removing untracked files - https://koukia.ca/how-to-remove-local-untracked-files-from-the-current-git-branch-571c6ce9b6b1
git clean -n - to check which files will be deleted.
git clean -f - to delete untracked files.