after push a commit to github undo code example

Example 1: git undo pushed commit

git reset <previous label or sha1>
git commit -am "commit message"
git push -f <remote-name> <branch-name>  //  git push -f origin master

Example 2: github undo last pushed commit

git reset <previous label or sha1>
git commit -am "blabla"
git push -f <remote-name> <branch-name>