Undo file git add to add

git add to add extra files 

git add. indicates that the current directory of all files, not careful it will submit additional documents

git add If you add the wrong file, then

Undo

git status look at the add files 
git reset HEAD if not now, then later what is on the inside of all time add withdrew 
git reset HEAD XXX.py is to file a py withdrawn

git reset HEAD file even revocation of file folders