$ git reset --hard
This command will remove the staged and working directory modifications. But you have to be very careful while using this command so that you don't end up deleting something you don't want to delete.
So, I think the safest way to deal with this is:
Dry run the command and know what would be deleted before actually deleting anything:
$ git clean -nfd
Once you are sure about the files that you would be deleting perform the following:
$ git clean -fd