bug#35739: Bad signature from GNU ELPA

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: rcopley@gmail.com,  35739@debbugs.gnu.org,  npostavs@gmail.com
> Date: Fri, 24 May 2019 10:22:05 -0400
> 
> > I'd like us not to change that behavior by default.
> 
> I think in this case we need to define it (i.e. document what it means
> to insert decoded text into a unibyte buffer).

Why do we have to define that only for that specific function?

And why is that relevant to the issue at hand, which is not to make
backward-incompatible changes in existing APIs?