git stash drop            # drop top hash, stash@{0}
git stash drop stash@{n}  # drop specific stash - see git stash list

#git stash drop takes no parameter - which drops the top stash - or 
#a stash reference which looks like: stash@{n} which n nominates 
#which stash to drop. You can't pass a commit id to git stash drop