git: backup master branch and start form empty master

gistfile1.txt

; clone the repo
git clone <repository>
; make sure HEAD is master (optional)
git checkout master
; make a local backup of master branch
git branch -m master master_backup
; push local backup branch to server
git push -u origin master_backup
; checkout master using --orphan
git checkout --orphan master
; do a hard reset (removes all files)
git reset --hard
; create a readme (for initial commit)
touch README.md
; make changes and commit
git add .
git commit -m 'Initial commit'
; push new master to server using force
git push origin master --force