bug#58192: 28.2; RCS integration issue

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 30 Sep 2022 14:45:34 +0200 (CEST)
> From: "Meyer, Thomas" <Thomas.Meyer@dla-marbach.de>
> Cc: 58192@debbugs.gnu.org
> 
> thanks, using the rcs port from https://sourceforge.net/projects/ezwinports/,
> I cannot reproduce the issue!

OK, so I guess it isn't Emacs's fault after all.

> The issue must then lie within Cygwin, or within the coupling of both
> through the wrapper script, this will require some deeper digging at
> our side I guess.

Yes, I agree.

> Do you believe that it will be sufficient to work with RCS version
> 5.7.1 from 2006?

It is good enough for my purposes, but I cannot tell more than that.

That port does include quite a few of Windows-specific changes, to
make it work reliably on Windows.

> Cygwin says
> 
>   rcs --version
>   rcs (GNU RCS) 5.10.1
>   Copyright (C) 2010-2022 Thien-Thi Nguyen
>   Copyright (C) 1990-1995 Paul Eggert
>   Copyright (C) 1982,1988,1989 Walter F. Tichy, Purdue CS
>   ...
> 
> My hope was that recent versions of RCS might be capable of handling
> the UCS-2 LE BOM (UTF-16) format used by windows registry files, but I
> did not check yet.

That would need RCS to support 'wchar_t *' strings, which I'd be
surprised if it did.  The "usual" way of Unix programs to deal with
non-ASCII text is to assume it's in UTF-8, not UTF-16, which allows to
keep using 'char *' strings.  Cygwin uses UTF-8 as its main encoding,
so my bet is that the Cygwin port of RCS relies on UTF-8 encoding.
But those are just guesses; I never had time to study all the recent
changes to RCS.