> Correct me I'm I'm wrong but I think were talking about using `git reset HEAD^` for splitting a commit.

I wasn't. I wanted to do the same as in the FAQ entry we are talking about, so I wanted to reset it to an older commit representing the same change (i.e. before an amend that we are now reverting). This is likely in a rebase, but we can always rebase later and only do the splitting now.

> With `--mixed`, it will also move the index back one step, so the index is empty (relative to HEAD)

Yes and this is the default (without any flag).

> That's what meant when I said "`git reset` by itself doesn't split a commit", because you need to do something like this:

That's what the `--soft` is for, then `git reset` does not touch the index.

> Just that additional steps are needed.

The only "additional" step required is specifying a commit message, which, as I said earlier, to me is a sensible default.

What I suggested applied on this case would be:

    git commit -m tmp
    git checkout @~
    git reset --soft previous-version # which you get from the reflog
    git commit -C @
    git rebase @~ branch-you-were-on --onto=@  # not of much use, when you only have a single commit you are throwing away in the next step, but when you are editing something earlier, this is likely what you want.
    git reset @~

    git commit -m tmp
    git rebase @~2 # break after first commit
    git reset --soft previous-version
    git commit -C @
    git rebase --continue
    git reset @~

    git rebase -i @~ --autostash # break after first commit
    git reset --soft previous-version
    git commit -C @
    git rebase --continue

Actually what you can also do, but this doesn't use reset, is this:

    git rebase -i @~ --autostash
    # add as the first line:
    pick previous-version
    git rebase --continue

Honestly, what I do most of the time to split commits (when there isn't an older version I want to split it to) is to just amend and then unselect the changes I don't want with the cursor.