bug#63949: 30.0.50; `vc-print-log´ does not erase buffer when called from *vc-change-log* buffer, at least for CVS logs

[Eli Zaretskii]

> Cc: 63949@debbugs.gnu.org
> Date: Fri, 9 Jun 2023 00:10:57 +0200
> From:  Jens Schmidt via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Caused by commit d494833d47968fcd97ba549654a259d6fb6c2eee.

Which means this was a regression in Emacs 28, and we should try to
fix it in Emacs 29.

> There is another subtle change to (most likely) that, which seems to 
> affect all backends: When calling `vc-print-log' from 
> *vc-change-buffer*, it now modifies the VC parent buffer to itself, 
> which is of course incorrect.

What do you mean by "modifies the VC parent buffer to itself"?  Do you
mean that vc-print-log makes the *vc-change-buffer* be the VC parent
buffer?  If so, why is this incorrect?