[BUG] rebase --onto doesn't abort properly

Hi,

On the latest git, I noticed that a rebase --onto doesn't abort
properly. Steps to reproduce:

  # on some topic branch
  $ git rebase --onto master @~10
  ^C # quickly!
  $ git rebase --abort
  # HEAD is still detached

I tried going back a few revisions, and the bug seems to be very old;
I'm surprised I didn't notice it earlier.

Are others able to reproduce this?

Thanks.

Ram