`@` alias for `HEAD` not working in `git push -u origin @`

From: Mark Florian <mflorian@gitlab.com>
Date: Jul 10, 2019, 05:06 UTC
Message-ID: <CANC=f2c8eynWJ1r=zwZq1qwrDE85LVFMU2mjLU26HYMDGaD4iA@mail.gmail.com>

Hello!

I learned today that `@` is a shortcut for `HEAD`. From `git help reivisions`:

    @ alone is a shortcut for HEAD.

However, when I tried to use it in a command I frequently use, I got an error:

    $ git push -u origin @
    fatal: invalid refspec '@'

I'm running git version 2.22.0 on Linux.

Is this a bug, or have I misunderstood how this is supposed to work?

Cheers, Mark