How to delete files permanently from your local and remote git repositories

gistfile1.txt

  git filter-branch -f --index-filter "git rm -rf --cached --ignore-unmatch FOLDERNAME" -- --all

Replace FOLDERNAME with the file or folder you wish to remove from the given git repository.
Once this is done run the following commands to clean up the local repository

  rm -rf .git/refs/original/
  git reflog expire --expire=now --all
  git gc --prune=now
  git gc --aggressive --prune=now

Now push all the changes to the remote repository

  git push --all --force