bug#5440: 23.1; buffer-file-format encoding temp buffers not reentrant

[Eli Zaretskii]

> From: Andrew Hyatt <ahyatt@gmail.com>
> Date: Thu, 21 Jul 2016 00:33:17 -0400
> Cc: 5440@debbugs.gnu.org
> 
> This reproduces on Emacs 25.  But I wonder if this should be a wishlist
> instead of a bug.  As the original report notes, decoding a buffer
> while encoding another buffer doesn't seem like a normal use-case.
> 
> If no one objects in the next few weeks, I can wishlist this.  Making it
> a minor-severity bug also seems reasonable to me.

I agree.  I also suggest to amend the documentation to make this issue
more explicitly mentioned.  The ELisp manual already says

 -- Variable: format-alist
     This list contains one format definition for each defined file
     format.            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     ^^^^^^

"Only one format definition per format."  But I think it won't do any
harm to specifically warn about violating that.

Thanks.