bug#60796: 27.1; Opening file ending in .sh inside a directory ending in .deb causes hang/100% thread usage

[Casey Connor]

When I do this:

$ mkdir test.deb
$ cd test.deb
$ emacs -Q test.sh

...emacs opens but is hung: 100% usage of a core, apparently
indefinitely. So far it seems to be the case that the directory must end
in ".deb" and the file edited must end in ".sh".


In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, 
cairo version 1.16.0)
of 2022-01-24, modified by Debian built on lgw01-amd64-048
System Description: Ubuntu 22.10

Recent messages:
Package autoconf removed but not purged. Skipping setup.
Loading /etc/emacs/site-start.d/50autoconf.el (source)...done
Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)...
Loading debian-ispell...
Loading /var/cache/dictionaries-common/emacsen-ispell-default.el 
(source)...done
Loading debian-ispell...done
Loading /var/cache/dictionaries-common/emacsen-ispell-dicts.el 
(source)...done
Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...

Configured using:
'configure --build x86_64-linux-gnu --prefix=/usr
--sharedstatedir=/var/lib --libexecdir=/usr/lib
--localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --enable-libsystemd --with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/27.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/27.1/site-lisp:/usr/share/emacs/site-lisp 

--with-sound=alsa --without-gconf --with-mailutils --build
x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib
--infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
--with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/27.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/27.1/site-lisp:/usr/share/emacs/site-lisp 

--with-sound=alsa --without-gconf --with-mailutils --with-cairo
--with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
'CFLAGS=-g -O2
-ffile-prefix-map=/build/emacs-NbbgEv/emacs-27.1+1=. 
-fstack-protector-strong
-Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
-D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD
JSON PDUMPER LCMS2 GMP

Important settings:
value of $LANG: en_US.UTF-8
locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
cl-old-struct-compat-mode: t
tooltip-mode: t
global-eldoc-mode: t
eldoc-mode: t
mouse-wheel-mode: t
tool-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
column-number-mode: t
line-number-mode: t
transient-mark-mode: t

Load-path shadows:
/usr/share/emacs/site-lisp/elpa/cmake-mode-3.24.2/cmake-mode-pkg hides 
/usr/share/emacs/site-lisp/elpa-src/cmake-mode-3.24.2/cmake-mode-pkg
/usr/share/emacs/site-lisp/elpa/cmake-mode-3.24.2/cmake-mode hides 
/usr/share/emacs/site-lisp/elpa-src/cmake-mode-3.24.2/cmake-mode
/usr/share/emacs/site-lisp/elpa/cmake-mode-3.24.2/cmake-mode-autoloads 
hides 
/usr/share/emacs/site-lisp/elpa-src/cmake-mode-3.24.2/cmake-mode-autoloads

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml mml-sec epa derived epg epg-config gnus-util
rmail rmail-loaddefs text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils term/xterm
xterm cus-edit cus-start cus-load wid-edit darktooth-theme autothemer
dash finder-inf edmacro kmacro package easymenu browse-url url-handlers
url-parse auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json subr-x map url-vars seq byte-opt gv bytecomp
byte-compile cconv cl-loaddefs cl-lib tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu 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 charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
x multi-tty make-network-process emacs)

Memory information:
((conses 16 170009 7221)
(symbols 48 14131 1)
(strings 32 48178 1329)
(string-bytes 1 1318531)
(vectors 16 16147)
(vector-slots 8 204540 7548)
(floats 8 36 561)
(intervals 56 262 0)
(buffers 1000 12))