bug#81480: 31.0.91; diff-mode-test-* incorrectly assumes "diff -a"

> From: Sean Whitton <[email protected]>
> Cc: [email protected], [email protected]
> Date: Thu, 30 Jul 2026 12:17:28 +0100
> 
> Eli Zaretskii [27/Jul  4:57pm +03] wrote:
> >> From: Sean Whitton <[email protected]>
> >> Date: Mon, 27 Jul 2026 10:30:28 +0100
> >>
> >> Paul Eggert [24/Jul  1:55pm -07] wrote:
> >> > This follows up on bug#81465 "31.0.91; ‘make check’ failures on Solaris
> >> > 10 sparc 32-bit" and I am splitting this issue off into a separate bug
> >> > report.
> >> >
> >> > Some diff-mode-test-* patches fail because they use ‘diff -a’. The -a
> >> > option is a GNU extension to POSIX and is not supported by Solaris 10 diff.
> >>
> >> I don't understand what you mean by saying that they *use* 'diff -a' --
> >> if it's -a that turns on the "No newline at end of file" output, then
> >> the problem has to be that -a is the implicit default behaviour for GNU
> >> diff?
> >
> > No, AFAICT, the "No newline at end of file" is a separate problem.
> >
> >> AFAICT we don't explicitly pass -a anywhere.
> >
> > We do, in smerge-refine-regions (which these tests invoke indirectly,
> > see the backtraces from the failing tests).
> 
> Thanks, I got confused somehow there.  Let's fix this along the lines
> of your patch.

I will, assuming Paul confirms that they fix the problem.