Insert a blank root commit on an existing repo

root_commit.sh

# from http://stackoverflow.com/a/647451


git symbolic-ref HEAD refs/heads/newroot
git rm --cached -r .
git clean -f -d

# then you apply the same steps
git commit --allow-empty -m 'root commit'
git cherry-pick $(git rev-list --reverse master | head -1)
git rebase --onto newroot newroot master
git branch -d newroot