To revert changes made to your working copy, do this:
git checkout .
Or equivalently, for git version >= 2.23:
git restore .
To revert changes made to the index (i.e., that you have added), do this. Warning this will reset all of your unpushed commits to master!:
To revert a change that you have committed:
git revert <commit 1> <commit 2>
To remove untracked files (e.g., new files, generated files):
git clean -f
Or untracked directories (e.g., new or automatically generated directories):
git clean -fd