Subject: bug#57114: 29.0.50; texinfo-format-buffer in auth.texi leads to backtrace

From: Stefan Kangas <[email-masked]>
Date: Wed, 10 Aug 2022 05:24:57 -0700

Running `texinfo-format-buffer' in "doc/misc/auth.texi" leads to:

Debugger entered--Lisp error: (file-missing "Opening input file" "No
such file or directory"
"/home/skangas/wip/emacs/doc/misc/docstyle.texi")
  insert-file-contents("/home/skangas/wip/emacs/doc/misc/docstyle.texi"
nil nil nil nil)
  apply(insert-file-contents
("/home/skangas/wip/emacs/doc/misc/docstyle.texi" nil nil nil nil))
  openwith-file-handler(insert-file-contents
"/home/skangas/wip/emacs/doc/misc/docstyle.texi" nil nil nil nil)
  texinfo-format-buffer-1()
  texinfo-format-buffer(nil)
  funcall-interactively(texinfo-format-buffer nil)
  command-execute(texinfo-format-buffer)

The same seems to be true for most other manuals in doc/misc/*.texi but
I only tried a handful of them.  One idea is that any file including the
below line will have the same problem:

    @include docstyle.texi