Truncate git history

gistfile1.txt

https://stackoverflow.com/questions/41953300/how-to-delete-the-old-git-history

git checkout --orphan temp <f>      # checkout to the status of the git repo at commit f; creating a branch named "temp"
git commit -m "new root commit"     # create a new commit that is to be the new root commit
git rebase --onto temp <f> master   # now rebase the part of history from <f> to master onthe temp branch
git branch -D temp                  # we don't need the temp branch anymore