Subject: 29.4; Dash character "-" appears as diff when it is the leading character in a line in a patch

From: Husain Alshehhi <[email-masked]>
Date: Sun, 26 Jan 2025 21:39:35 -0600

diff-mode does not handle a patch very well. In particular, if a patch
contains the commit message, and if the commit message contains a dash
character "-" at the beginning of a line, diff-mode interprets this as a
diff rather than part of the commit message.

To replicate this bug: copy the following in a file (e.g. test.patch),
open it in diff-mode, and you will see that the line "- unordered lists"
shows up in `diff-indicator-removed' face:

--8<---------------cut here---------------start------------->8---
From: [email-masked]
Date: Thu, 01 Jan 2025 00:00:00 -0000
Subject: [PATCH] Adding a comment

This is a commit to test emacs mode for displaying dash "-" character
such as:

- unordered lists        << This will be displayed as a diff.
- with multiple items    << So will this.

Emacs shows unordered lists as part of the diff because they start with
"-".
---
  main.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/main.c b/main.c
index 5df43ae..43b62fa 100644
--- a/main.c
+++ b/main.c
@@ -1,4 +1,5 @@
  int main() {
+  // adding a comment.
    printf("hello world");
    return 0;
  }
-- 

2.47.1
--8<---------------cut here---------------end--------------->8---

See
https://lists.gnu.org/archive/html/help-gnu-emacs/2025-01/msg00229.html
for reference.

In GNU Emacs 29.4 (build 2, x86_64-suse-linux-gnu, GTK+ Version 3.24.43,
cairo version 1.18.2)
System Description: openSUSE Tumbleweed

Configured using:
  'configure --disable-build-details --without-pop --with-mailutils
  --with-native-compilation --without-hesiod --with-gameuser=:games
  --with-kerberos --with-kerberos5 --with-file-notification=inotify
  --with-modules --enable-autodepend --prefix=/usr
  --mandir=/usr/share/man --infodir=/usr/share/info --datadir=/usr/share
  --localstatedir=/var --sharedstatedir=/var/lib
  --libexecdir=/usr/libexec --with-file-notification=yes
  --libdir=/usr/lib64
  --enable-locallisppath=/usr/share/emacs/29.4/site-lisp:/usr/share/emacs/site-lisp
  --with-x --with-xim --with-sound --with-xpm --with-jpeg --with-tiff
  --with-gif --with-png --with-rsvg --with-dbus --with-webp --with-xft
  --with-imagemagick --without-gpm --with-x-toolkit=gtk3 --with-pgtk
  --with-toolkit-scroll-bars --x-includes=/usr/include
  --x-libraries=/usr/lib64 --with-libotf --with-m17n-flt --with-cairo
  --with-xwidgets --build=x86_64-suse-linux --with-dumping=pdumper
  'CFLAGS=-O2 -Wall -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3
  -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables
  -fstack-clash-protection -Werror=return-type -flto=auto -g
  -D_GNU_SOURCE -DGDK_DISABLE_DEPRECATION_WARNINGS
  -DGLIB_DISABLE_DEPRECATION_WARNINGS -pipe -Wno-pointer-sign
  -Wno-unused-variable -Wno-unused-label -fno-optimize-sibling-calls
  -DPDMP_BASE='\''"emacs-wayland"'\''' LDFLAGS=-Wl,-O2'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ
IMAGEMAGICK JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK PNG RSVG SECCOMP SOUND SQLITE3
THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XIM XWIDGETS GTK3 ZLIB

Important settings:
   value of $LC_NUMERIC: POSIX
   value of $LANG: en_US.UTF-8
   value of $XMODIFIERS: @im=local
   locale-coding-system: utf-8-unix

Major mode: Article

Minor modes in effect:
   org-roam-db-autosync-mode: t
   global-git-commit-mode: t
   magit-auto-revert-mode: t
   shell-dirtrack-mode: t
   global-corfu-mode: t
   corfu-mode: t
   vertico-mode: t
   which-key-mode: t
   override-global-mode: t
   tooltip-mode: t
   global-eldoc-mode: t
   show-paren-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   buffer-read-only: t
   column-number-mode: t
   line-number-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t

Load-path shadows:
/home/husain/.emacs.d/elpa/compat-29.1.4.2/compat hides 
/usr/share/emacs/site-lisp/compat
/home/husain/.emacs.d/elpa/compat-29.1.4.2/compat-29 hides 
/usr/share/emacs/site-lisp/compat-29
/home/husain/.emacs.d/elpa/compat-29.1.4.2/compat-28 hides 
/usr/share/emacs/site-lisp/compat-28
/home/husain/.emacs.d/elpa/compat-29.1.4.2/compat-27 hides 
/usr/share/emacs/site-lisp/compat-27
/home/husain/.emacs.d/elpa/compat-29.1.4.2/compat-26 hides 
/usr/share/emacs/site-lisp/compat-26
/home/husain/.emacs.d/elpa/compat-29.1.4.2/compat-25 hides 
/usr/share/emacs/site-lisp/compat-25
/home/husain/.emacs.d/elpa/transient-20230919.2146/transient hides 
/usr/share/emacs/29.4/lisp/transient
/home/husain/.emacs.d/elpa/jsonrpc-1.0.24/jsonrpc hides 
/usr/share/emacs/29.4/lisp/jsonrpc
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package hides 
/usr/share/emacs/29.4/lisp/use-package/use-package
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-lint 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-lint
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-jump 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-jump
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-ensure 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-ensure
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-diminish 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-diminish
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-delight 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-delight
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-core 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-core
/home/husain/.emacs.d/elpa/use-package-20230426.2324/use-package-bind-key 
hides /usr/share/emacs/29.4/lisp/use-package/use-package-bind-key
/home/husain/.emacs.d/elpa/bind-key-20230203.2004/bind-key hides 
/usr/share/emacs/29.4/lisp/use-package/bind-key
/home/husain/.emacs.d/elpa/eglot-1.17/eglot hides 
/usr/share/emacs/29.4/lisp/progmodes/eglot
/home/husain/.emacs.d/elpa/eldoc-1.15.0/eldoc hides 
/usr/share/emacs/29.4/lisp/emacs-lisp/eldoc

Features:
(mailalias mailclient dabbrev mm-archive misearch multi-isearch shadow
bbdb-message emacsbug mule-util smiley gnus-cite message-view-patch
mail-extr textsec uni-scripts idna-mapping ucs-normalize uni-confusable
textsec-check gnus-bcklg gnus-async sort gnus-ml disp-table
cello-light-theme ef-cherie-theme ef-themes consult nndraft nnmh
nnmaildir bbdb-gnus nnnil gnus-agent gnus-srvr gnus-score score-mode
nnvirtual gnus-msg gnus-art mm-uu mml2015 mm-view mml-smime smime gnutls
dig nntp gnus-cache gnus-sum gnus-group gnus-undo gnus-start gnus-dbus
dbus gnus-cloud nnimap nnmail mail-source utf7 nnoo parse-time gnus-spec
gnus-int gnus-range gnus-win org-roam-protocol org-protocol
org-roam-migrate org-roam-log org-roam-mode org-roam-capture org-roam-id
org-roam-node org-roam-db emacsql-sqlite-builtin sqlite org-roam-utils
org-roam-compat org-roam org-capture org-attach emacsql-sqlite
emacsql-sqlite-common emacsql emacsql-compiler elfeed-show elfeed-search
vc-git vc-dispatcher elfeed-csv elfeed elfeed-curl elfeed-log elfeed-db
elfeed-lib url-queue xml-query erc-goodies erc iso8601 erc-backend
erc-networks erc-common erc-compat erc-loaddefs bbdb-mua bbdb-com bbdb
bbdb-site timezone gnus nnheader range org-noter org-noter-djvu
org-noter-nov nov recentf tree-widget shr pixel-fill kinsoku url-file
svg xml esxml-query dom org-noter-pdf org-noter-core pdf-tools cus-edit
cus-load wid-edit pdf-view magit-bookmark bookmark pp jka-compr
pdf-cache pdf-info tq pdf-util pdf-macs image-mode exif ledger-mode
ledger-check ledger-texi ledger-test ledger-sort ledger-report
ledger-reconcile ledger-occur ledger-fonts ledger-fontify ledger-state
ledger-complete ledger-schedule ledger-init ledger-xact ledger-post
ledger-exec ledger-navigate eshell esh-cmd esh-ext esh-opt esh-proc
esh-io esh-arg esh-module esh-groups esh-util files-x ledger-context
ledger-commodities ledger-regex scad-mode ox-gfm htmlize ob-latex ox-odt
rng-loc rng-uri rng-parse rng-match rng-dt rng-util rng-pttrn nxml-parse
nxml-ns nxml-enc xmltok nxml-util ox-md ox-latex ox-icalendar ox-html
table ox-ascii ox-publish ox org-habit org-agenda org-element
org-persist xdg org-id org-refile org ob ob-tangle ob-ref ob-lob
ob-table org-macro org-src ob-comint org-pcomplete org-list org-footnote
org-faces org-entities noutline outline ob-emacs-lisp org-table org-keys
org-loaddefs find-func avl-tree ol oc ob-exp ob-core org-cycle org-fold
org-fold-core org-compat ob-eval org-version org-macs link-hint
goto-addr avy cal-menu calendar cal-loaddefs ediff ediff-merg ediff-mult
ediff-wind ediff-diff ediff-help ediff-init ediff-util git-link
magit-submodule magit-blame magit-stash magit-reflog magit-bisect
magit-push magit-pull magit-fetch magit-clone magit-remote magit-commit
magit-sequence magit-notes magit-worktree magit-tag magit-merge
magit-branch magit-reset magit-files magit-refs magit-status magit
magit-repos magit-apply magit-wip magit-log which-func imenu magit-diff
smerge-mode diff diff-mode git-commit log-edit message sendmail
yank-media puny dired dired-loaddefs rfc822 mml mml-sec epa derived epg
rfc6068 epg-config gnus-util mm-decode mm-bodies mm-encode mail-parse
rfc2231 rfc2047 rfc2045 mm-util ietf-drums mail-prsvr mailabbrev
mail-utils gmm-utils mailheader pcvs-util add-log magit-core
magit-autorevert autorevert filenotify magit-margin magit-transient
magit-process with-editor time-date shell pcomplete server magit-mode
transient magit-git magit-base magit-section format-spec cursor-sensor
crm dash edmacro kmacro sqlformat reformatter go-mode find-file ffap
thingatpt etags fileloop generator xref project scala-mode
scala-mode-prettify-symbols scala-mode-imenu scala-mode-map
scala-mode-fontlock scala-mode-indent scala-mode-paragraph
scala-mode-syntax scala-mode-lib typescript-mode cc-mode cc-fonts
cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
compile text-property-search comint ansi-osc ring yaml-mode ansi-color
exec-path-from-shell corfu orderless vertico compat diminish which-key
use-package use-package-ensure use-package-delight use-package-diminish
use-package-bind-key bind-key use-package-core finder-inf comp comp-cstr
warnings icons rx cl-extra help-mode ispell bbdb-autoloads
corfu-autoloads diminish-autoloads ef-themes-autoloads eglot-autoloads
eldoc-autoloads elfeed-autoloads emacs-everywhere-autoloads
embark-consult-autoloads consult-autoloads embark-autoloads
exec-path-from-shell-autoloads f-autoloads ggtags-autoloads
git-link-autoloads go-mode-autoloads htmlize-autoloads jsonrpc-autoloads
ledger-mode-autoloads link-hint-autoloads marginalia-autoloads
markdown-mode-autoloads magit-autoloads git-commit-autoloads
modus-themes-autoloads nov-autoloads orderless-autoloads
org-noter-autoloads org-roam-autoloads magit-section-autoloads
emacsql-autoloads ox-gfm-autoloads pdf-tools-autoloads request-autoloads
scad-mode-autoloads scala-mode-autoloads show-font-autoloads
sqlformat-autoloads reformatter-autoloads standard-themes-autoloads
tablist-autoloads transient-autoloads treemacs-autoloads
posframe-autoloads ht-autoloads hydra-autoloads pfuture-autoloads
ace-window-autoloads avy-autoloads s-autoloads dash-autoloads
typescript-mode-autoloads use-package-autoloads bind-key-autoloads
vertico-autoloads w3m-load w3m-autoloads which-key-autoloads
with-editor-autoloads info compat-autoloads yaml-mode-autoloads
auctex-autoloads tex-site package browse-url url url-proxy url-privacy
url-expand url-methods url-history url-cookie generate-lisp-file
url-domsuf url-util mailcap url-handlers url-parse auth-source cl-seq
eieio eieio-core cl-macs password-cache json subr-x map byte-opt gv
bytecomp byte-compile url-vars cl-loaddefs cl-lib rmc delsel lpr
easy-mmode pcase iso-transl tooltip cconv eldoc paren electric uniquify
ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/pgtk-win
pgtk-win term/common-win pgtk-dnd 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 nadvice seq simple cl-generic indonesian philippine
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 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 xwidget-internal dbusbind inotify dynamic-setting
system-font-setting font-render-setting cairo gtk pgtk lcms2 multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 1306461 97685)
  (symbols 48 47318 18)
  (strings 32 522080 13600)
  (string-bytes 1 26474941)
  (vectors 16 262284)
  (vector-slots 8 3657817 148039)
  (floats 8 1262 501)
  (intervals 56 4819 450)
  (buffers 984 34))