bug#61189: 29.0.60; Strange log-edit-mode M-q bug introduced in 27.1

[Eric Gillespie]

It's an old bug, but it requires such a specific kind of log
message to trigger that it took me until a few months ago to
finally hit it!

To reproduce:
0. open modified file under version control
1. C-x v v
2. Enter the following two-line message (i.e. replace "Summary:" and the rest):
bork bork bork bork bork bork bork bork bork bork bork bork bork
bork (e.g. bork) bork bork bork bork bork bork bork bork
3. M-q
4. M-q

(I have run with (setq log-edit-hook '(log-edit-show-files)) for a long time
and that's how I encountered the bug.)

Expected:
First M-q fills the paragraph to 70 columns.
Second does nothing.

Actual:
First M-q fills the paragraph to 70 columns.
Second moves one bork back from line one to line two, adds a colon, and
deletes the sapce before the opening parenthesis, resulting in:

bork bork bork bork bork bork bork bork bork bork bork bork bork
bork:(e.g. bork) bork bork bork bork bork bork bork bork

Bug introduced in commit 01661f33c11654d1fe5fe1013332db2500b7f449.



In GNU Emacs 29.0.60 (build 3, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0) of 2023-01-30 built on dogato
Repository revision: 86b03046c0097aa7bd342efe9b9fde711ed81755
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: openSUSE Leap 15.4

Configured using:
 'configure -C --prefix=/home/epg/.local --disable-silent-rules
 --without-libsystemd --without-xft --without-m17n-flt
 --without-toolkit-scroll-bars --without-gpm --without-dbus
 --without-gsettings --without-selinux --without-compress-install
 --with-x --with-tree-sitter
 TREE_SITTER_CFLAGS=-I/home/epg/src/tree-sitter/tree-sitter/lib/include
 TREE_SITTER_LIBS=/home/epg/src/tree-sitter/tree-sitter/libtree-sitter.a
 CC=gcc-11'

Configured features:
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NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM LUCID ZLIB

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Org

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

Load-path shadows:
None found.

Features:
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url-vars gnus-group gnus-undo gnus-start gnus-dbus dbus xml gnus-cloud
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gnus-range message sendmail mailcap yank-media puny rfc822 mml mml-sec
password-cache epa derived epg rfc6068 epg-config mm-decode mm-bodies
mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums mailabbrev
gmm-utils mailheader gnus-win gnus nnheader gnus-util
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cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc paren electric
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prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
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composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads inotify dynamic-setting
font-render-setting cairo x-toolkit xinput2 x multi-tty
make-network-process emacs)

Memory information:
((conses 16 187497 8623)
 (symbols 48 20567 0)
 (strings 32 71444 1778)
 (string-bytes 1 2202630)
 (vectors 16 38089)
 (vector-slots 8 427107 12649)
 (floats 8 268 117)
 (intervals 56 413 0)
 (buffers 984 12))