Merge from origin/emacs-27

a2b07f9f11 (origin/emacs-27) ; * etc/NEWS: Explain how to get back ol...
b468b3d1ff Fix a recent documentation change
1ab766fd58 Fix last change
ecfe633993 * lisp/tab-bar.el: Last-minute changes.
c1ce9fa7f2 * lisp/subr.el (cancel-change-group): Fix bug#39680
ef5744a988 Improve docs for horizontal scrolling with mouse and touch...
1bc3fa0bd0 * lisp/emacs-lisp/package.el (package-install): Fix typo i...
4537976afd Port .gdbinit to clang with -gdwarf-4
0883c800a0 Simplify rx example in manual
a695189248 ; * etc/NEWS: Fix typo.

# Conflicts:
#	etc/NEWS

8 files changed, 57 insertions, 19 deletions

diff --git a/doc/emacs/frames.texi b/doc/emacs/frames.texi
index 002297c2599..7a583b96bbd 100644
--- a/doc/emacs/frames.texi
+++ b/doc/emacs/frames.texi
@@ -217,10 +217,15 @@ default bound to scrolling with the @key{Ctrl} modifier.
 @vindex mouse-wheel-tilt-scroll
 @vindex mouse-wheel-flip-direction
 Emacs can also support horizontal scrolling if your mouse's wheel can
-be tilted.  This feature is off by default; the variable
-@code{mouse-wheel-tilt-scroll} turns it on.  If you'd like to reverse
-the direction of horizontal scrolling, customize the variable
-@code{mouse-wheel-flip-direction} to a non-@code{nil} value.
+be tilted, or if your touchpad supports it.  This feature is off by
+default; the variable @code{mouse-wheel-tilt-scroll} turns it on, if
+you customize it to a non-@code{nil} value.  By default, tilting the
+mouse wheel scrolls the window's view horizontally in the direction of
+the tilt: e.g., tilting to the right scrolls the window to the right,
+so that the text displayed in the window moves horizontally to the
+left.  If you'd like to reverse the direction of horizontal scrolling,
+customize the variable @code{mouse-wheel-flip-direction} to a
+non-@code{nil} value.
 
 When the mouse pointer is over an image, scrolling the mouse wheel
 with the @key{Ctrl} modifier scales the image under the mouse pointer.
diff --git a/doc/lispref/searching.texi b/doc/lispref/searching.texi
index 1a090ebe101..83c154938cd 100644
--- a/doc/lispref/searching.texi
+++ b/doc/lispref/searching.texi
@@ -1021,8 +1021,8 @@ or, using shorter synonyms and written more compactly,
 @example
 @group
 (rx "/*"
-    (* (| (not (any "*"))
-          (: "*" (not (any "/")))))
+    (* (| (not "*")
+          (: "*" (not "/"))))
     (+ "*") "/")
 @end group
 @end example
diff --git a/etc/NEWS.27 b/etc/NEWS.27
index 1eff9261147..63003191699 100644
--- a/etc/NEWS.27
+++ b/etc/NEWS.27
@@ -360,6 +360,14 @@ its '--eval' command-line option), as well as in
 'lisp-interaction-mode' and 'ielm-mode', used in the "*scratch*" and
 "*ielm*" buffers.
 
+We envision that most Lisp code is already either written with
+lexical-binding in mind, or will work unchanged under
+lexical-binding.  If, for some reason, your code used in 'M-:' or
+'--eval' doesn't work as result of this change, either modify the code
+to work with lexical binding, or wrap it in an extra level of 'eval'.
+For example, --eval FORM becomes --eval "(eval 'FORM)" (note the extra
+quote in 'FORM).
+
 ---
 ** The new user option 'tooltip-resize-echo-area' avoids truncating
 tooltip text on GUI frames when tooltips are displayed in the echo
@@ -779,7 +787,7 @@ an offset to absolute line numbers.
 ** table
 
 +++
-*** 'table-generate-source' now supports wiki and mediawiki
+*** 'table-generate-source' now supports wiki and mediawiki.
 This command can now output wiki and mediawiki format tables.
 
 ** telnet-mode
diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index 6d6b31f1f38..bce17a04ba7 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -2045,7 +2045,7 @@ Mark the installed package as selected by adding it to
 
 When called from Lisp and optional argument DONT-SELECT is
 non-nil, install the package but do not add it to
-`package-select-packages'.
+`package-selected-packages'.
 
 If PKG is a `package-desc' and it is already installed, don't try
 to install it but still mark it as selected."
diff --git a/lisp/mwheel.el b/lisp/mwheel.el
index 56150c803f7..317f2cd8edd 100644
--- a/lisp/mwheel.el
+++ b/lisp/mwheel.el
@@ -145,13 +145,19 @@ face height."
 ;;; For tilt-scroll
 ;;;
 (defcustom mouse-wheel-tilt-scroll nil
-  "Enable scroll using tilting mouse wheel."
+  "Enable horizontal scrolling by tilting mouse wheel or via touchpad.
+Also see `mouse-wheel-flip-direction'."
   :group 'mouse
   :type 'boolean
   :version "26.1")
 
 (defcustom mouse-wheel-flip-direction nil
-  "Swap direction of `wheel-right' and `wheel-left'."
+  "Swap direction of `wheel-right' and `wheel-left'.
+By default, `wheel-right' scrolls the text to the right,
+and `wheel-left' scrolls in the other direction.
+If this variable is non-nil, it inverts the direction of
+horizontal scrolling by tilting the mouse wheel.
+Also see `mouse-wheel-tilt-scroll'."
   :group 'mouse
   :type 'boolean
   :version "26.1")
diff --git a/lisp/subr.el b/lisp/subr.el
index 9c80c06a127..123557e736b 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2987,13 +2987,18 @@ This finishes the change group by reverting all of its changes."
         ;; the body of `atomic-change-group' all changes can be undone.
         (widen)
         (let ((old-car (car-safe elt))
-              (old-cdr (cdr-safe elt)))
+              (old-cdr (cdr-safe elt))
+              ;; Use `pending-undo-list' temporarily since `undo-more' needs
+              ;; it, but restore it afterwards so as not to mess with an
+              ;; ongoing sequence of `undo's.
+              (pending-undo-list
+               ;; Use `buffer-undo-list' unconditionally (bug#39680).
+               buffer-undo-list))
           (unwind-protect
               (progn
                 ;; Temporarily truncate the undo log at ELT.
                 (when (consp elt)
                   (setcar elt nil) (setcdr elt nil))
-                (unless (eq last-command 'undo) (undo-start))
                 ;; Make sure there's no confusion.
                 (when (and (consp elt) (not (eq elt (last pending-undo-list))))
                   (error "Undoing to some unrelated state"))
diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 873f54a27db..30ed1a4cf68 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -123,7 +123,8 @@ Possible modifiers are `control', `meta', `shift', `hyper', `super' and
                     (assq-delete-all 'tab-bar-lines
                                      default-frame-alist)))))
 
-  (when (and tab-bar-mode (not (get-text-property 0 'display tab-bar-new-button)))
+  (when (and tab-bar-mode tab-bar-new-button
+             (not (get-text-property 0 'display tab-bar-new-button)))
     ;; This file is pre-loaded so only here we can use the right data-directory:
     (add-text-properties 0 (length tab-bar-new-button)
                          `(display (image :type xpm
@@ -132,7 +133,8 @@ Possible modifiers are `control', `meta', `shift', `hyper', `super' and
                                           :ascent center))
                          tab-bar-new-button))
 
-  (when (and tab-bar-mode (not (get-text-property 0 'display tab-bar-close-button)))
+  (when (and tab-bar-mode tab-bar-close-button
+             (not (get-text-property 0 'display tab-bar-close-button)))
     ;; This file is pre-loaded so only here we can use the right data-directory:
     (add-text-properties 0 (length tab-bar-close-button)
                          `(display (image :type xpm
@@ -263,6 +265,17 @@ before calling the command that adds a new tab."
   :group 'tab-bar
   :version "27.1")
 
+(defcustom tab-bar-new-button-show t
+  "If non-nil, show the \"New tab\" button in the tab bar.
+When this is nil, you can create new tabs with \\[tab-new]."
+  :type 'boolean
+  :initialize 'custom-initialize-default
+  :set (lambda (sym val)
+         (set-default sym val)
+         (force-mode-line-update))
+  :group 'tab-bar
+  :version "27.1")
+
 (defvar tab-bar-new-button " + "
   "Button for creating a new tab.")
 
@@ -306,7 +319,8 @@ This helps to select the tab by its number using `tab-bar-select-tab'."
   :group 'tab-bar
   :version "27.1")
 
-(defvar tab-bar-separator nil)
+(defvar tab-bar-separator nil
+  "String that delimits tabs.")
 
 
 (defcustom tab-bar-tab-name-function #'tab-bar-tab-name-current
@@ -464,9 +478,9 @@ Return its existing value or a new value."
                  (interactive)
                  (tab-bar-close-tab ,i)))))))
       tabs)
-     (when tab-bar-new-button
-       `((sep-add-tab menu-item ,separator ignore)
-         (add-tab menu-item ,tab-bar-new-button tab-bar-new-tab
+     `((sep-add-tab menu-item ,separator ignore))
+     (when (and tab-bar-new-button-show tab-bar-new-button)
+       `((add-tab menu-item ,tab-bar-new-button tab-bar-new-tab
                   :help "New tab"))))))
 
 
diff --git a/src/.gdbinit b/src/.gdbinit
index 5dd01337153..30c7b055ce0 100644
--- a/src/.gdbinit
+++ b/src/.gdbinit
@@ -72,7 +72,7 @@ end
 
 define xgetsym
   xgetptr $arg0
-  set $ptr = ((struct Lisp_Symbol *) ((char *)lispsym + $ptr))
+  set $ptr = ((struct Lisp_Symbol *) ((char *) &lispsym + $ptr))
 end
 
 # Access the name of a symbol