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 <eliz@gnu.org>]

> Date: Fri, 9 Jun 2023 00:44:39 +0200
> From:  Jens Schmidt via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Here come five patches for this issue, based on emacs-29:
> 
> 0001-Always-erase-log-buffer-before-calling-vc-print-log.patch
> 0002-Always-erase-log-buffer-before-calling-vc-print-log.patch
> 0003-Always-erase-log-buffer-before-calling-vc-print-log.patch

Please add comments there explaining the significance of the call to
vc-setup-buffer and its effect, depending on what is the current
buffer.

> 0005-Avoid-setting-circular-vc-parent-buffer.patch
> 
>    This one fixes the issue related to VC parent buffer described in the
>    previous update.  The "local" change seems to be logical (a buffer
>    should not be the VC parent buffer of itself), but I'm not quite sure
>    about any adverse "global" consequences.

This code is very old, so at the very least we need to track its
origin and understand why it was added, before discussing whether it
should be removed.  AFAICT, this code was introduced in commit
1a2f456b73bab4a711a51c8f84abf1d9f63a3b90, 30 years ago, and there's
some explanation of the rationale in the log message.

Thanks.