What is the difference between 'reset hard head' and 'reset hard'?

git, git-reset

Solution

`HEAD` is implied when you do not specify that argument.

However, you could do e.g. `git reset --hard HEAD^` to nuke the commit at HEAD, i.e. undo it in a way that rewrites history.

Problem

I am new to git, so question might be very easy, that what is the difference between `git reset --hard HEAD` and `git reset --hard`?

Original source