At date git prompts:
use "git rm --cached <file>..." to unstage
if files were not in the repo. It unstages the files keeping them there.use "git reset HEAD <file>..." to unstage
if the files were in the repo, and you are adding them as modified. It keeps the files as they are, and unstages them.At my knowledge you cannot undo the git add --
but you can unstage a list of files as mentioned above.