bug#38026: [PATCH] Explain negative NABS in `goto-history-element'.

[Eli Zaretskii]

> Cc: 38026@debbugs.gnu.org
> From: Hong Xu <hong@topbug.net>
> Date: Sat, 2 Nov 2019 10:07:03 -0700
> 
> On 11/2/19 1:03 AM, Eli Zaretskii wrote:
> > Thanks, but I don't see how this clarifies the issue.  Can you tell
> > more about your motivation?
> > 
> 
> The motivation is to clarify what a negative NABS means. From the current 
> document, it is unclear that NABS can be negative.

In that case, the patch is insufficient.  First, we don't document
minibuffer-default in the manual, so referencing it will leave the
reader wondering what it is, and how it is set and used.  Second, the
doc string of goto-history-element should also explain what is the
meaning of negative values.  And third, several functions bind
minibuffer-default to certain values, and I'm not sure this variable
can usefully be documented in a manual.

So I think the text needs not reference minibuffer-default, but
instead talk about "future history", like the Emacs manual does.

Thanks.