bug#34944: 27.0.50; FR: support amend in vc-hg

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Fri, 22 Mar 2019 11:44:02 +0100
> 
> The Git integration for vc.el supports amending commits via a magic
> changelog header.  Mercurial has the same functionality, see
> https://www.mercurial-scm.org/wiki/EditingHistory#Amending_the_latest_changeset_with_commit_--amend.
> If would be great to support this in Emacs as well.  Maybe the Git
> approach could even move into main VC, and made available to all
> backends that support amending?

Can you propose a patch for that?

Thanks.