git clean(1) -f -d
Remove untracked files from the working tree
-f, --force
    If the git configuration variable clean.requireForce is not set to false, git clean will refuse to
    run unless given -f or -n.
    Remove untracked directories in addition to untracked files. If an untracked directory is managed by
    a different git repository, it is not removed by default. Use -f option twice if you really want to
    remove such a directory.
source manpages: git-clean