bug#51523: 29.0.50; gnus-mime-view-part-externally very slow

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Gregory Heytings <gregory@heytings.org>,  51523@debbugs.gnu.org,
>   monnier@iro.umontreal.ca
> Date: Mon, 01 Nov 2021 17:59:32 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > What would be the purpose of replacing with an older file, but keeping
> > the old time stamp?
> 
> That's the interface I want.  If the file changes, in any noticeable
> way, then it...  changes.  Newer or not has nothing to do with it.

But the real answer to that question is to compare the contents, not
file's attributes.  Testing attributes is an approximation, and once
we are using an approximation, it is legitimate to ask when it's okay
for the approximation to fail.

Basically, comparing time stamps is what Make does, and Make doesn't
care about the time stamp becoming older.  So why should we?

And if by "I want" you mean Gnus, then maybe we should name this
function gnus-has-mailcap-file-changed-p, and stop pretending that it
has more general use?