bug#58192: 28.2; RCS integration issue

[Meyer, Thomas]

Dear emacs developers, we have an issue with vc-rcs, that we have been
using for a long time, and which seems to be broken in 28.2 (actually
first noticed this in 28.1): we are working on the Windows port
available on http://ftp.gnu.org/gnu/emacs/windows/emacs-28/.

By tracing the activity of e.g. ci command with process monitor, we
found that the commands fail because an erraneous line break is send
with the command, e.g.

----
PID: 7224, Command line: C:\Windows\system32\cmd.exe /c c:\bin\ci.cmd -j -u1 
"-mSummary: bla
" RCS/x.txt,v
----

To reproduce:

find new file in new directory
C-x v v (vc-next-action)
Registration will work fine (Registering 
(c:/Users/meyert/Documents/RCS-test/a.txt)... done)
change file
C-x v v (vc-next-action) -> first error: a checkout is done, erasing the changes
change file again
C-x v v (vc-next-action) -> second error: check-in fails:

   Press C-c C-c when you are done editing.
   Enter a change comment.  Type C-c C-c when done
   Checking in c:/Users/meyert/Documents/RCS-test/a.txt...
   progn: Failed (status 1): ci -j -u1 -mSummary: bla
    RCS/a.txt,v

Do you require further details?

We use Cygwin 3.3.5-1 for providing RCS under windows, but I guess
that this is not where the issue arises.

Kind regards, Thomas

generated info:

--------------------------------------------------------------------------------

In GNU Emacs 28.2 (build 2, x86_64-w64-mingw32)
 of 2022-09-13 built on AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Education (v10.0.2009.19044.2006)

Configured using:
 'configure --with-modules --without-dbus --with-native-compilation
 --without-compress-install CFLAGS=-O2'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
XPM ZLIB

(NATIVE_COMP present but libgccjit not available)

Important settings:
  value of $LANG: DEU
  locale-coding-system: cp1252

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug sendmail log-edit message rmc puny
rfc822 mml mml-sec epa epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs auth-source eieio eieio-core eieio-loaddefs
password-cache json map text-property-search mm-decode mm-bodies
mm-encode mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums
mail-prsvr mailabbrev mail-utils gmm-utils mailheader ring pcvs-util
add-log vc-filewise vc-mtn vc-hg rx vc-git diff-mode easy-mmode vc-bzr
vc-dir edmacro kmacro ewoc vc-src vc-sccs vc-svn vc-cvs vc-rcs cl-seq
pcase vc vc-dispatcher ediff ediff-merg ediff-mult cl-macs derived
ediff-wind ediff-diff ediff-help ediff-init ediff-util time-date subr-x
misearch multi-isearch seq byte-opt gv bytecomp byte-compile cconv
dired-aux cl-loaddefs cl-lib dired dired-loaddefs iso-transl tooltip
eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type
elisp-mode mwheel dos-w32 ls-lisp disp-table term/w32-win w32-win
w32-vars term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice button
loaddefs faces cus-face macroexp files window text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads w32notify w32 lcms2 multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 217438 15563)
 (symbols 48 11284 1)
 (strings 32 32118 2137)
 (string-bytes 1 1074223)
 (vectors 16 15876)
 (vector-slots 8 274294 17668)
 (floats 8 55 290)
 (intervals 56 6409 275)
 (buffers 992 31))