revert and reset git code example

Example: revert or reset git

git reset	Commit-level	Discard commits in a private branch or throw away uncommited changes
git reset	File-level	Unstage a file
git checkout	Commit-level	Switch between branches or inspect old snapshots
git checkout	File-level	Discard changes in the working directory
git revert	Commit-level	Undo commits in a public branch
git revert	File-level	(N/A)