commitsRemoved.txt

Open Git Shell... Then do the following to remove all commits:

If you are sure to remove all commit history, simply just remove the .git folder in your project root (note that its hidden). Then initialize a new repository in the same folder and link it to github:
git init
git remote add origin git@github.com:user/repo

now commit your current version of code
git add *
git commit -am 'message'

and finally force update on github:
git push -f origin master

However, I suggest backuping your repository (.git folder) before doing these steps!