How to delete untracked files in git

gistfile1.txt

# delete untracked files
git clean -f
 
# delete untracked files as well as the directories
git clean -fd
 
# including gitignore file/directories （慎用，一般这个是用来删掉编译出来的 .o之类的文件用的）
git clean -xfd
 
# before using git clean，with -n parameter to preview the files or directories will be deleted
git clean -nxfd
git clean -nf
git clean -nfd