GNU Emacs NEWS -- history of user-visible changes.

Copyright (C) 2022-2024 Free Software Foundation, Inc.
See the end of the file for license conditions.

Please send Emacs bug reports to 'bug-gnu-emacs@gnu.org'.
If possible, use 'M-x report-emacs-bug'.

This file is about changes in Emacs version 31.

See file HISTORY for a list of GNU Emacs versions and release dates.
See files NEWS.30, NEWS.29, ..., NEWS.18, and NEWS.1-17 for changes
in older Emacs versions.

You can narrow news to a specific version by calling 'view-emacs-news'
with a prefix argument or by typing 'C-u C-h C-n'.

Temporary note:
+++ indicates that all relevant manuals in doc/ have been updated.
--- means no change in the manuals is needed.
When you add a new item, use the appropriate mark if you are sure it
applies, and please also update docstrings as needed.

\f
* Installation Changes in Emacs 31.1

** Changed GCC default options on 32-bit x86 systems.
When using GCC 4 or later to build Emacs on 32-bit x86 systems,
'configure' now defaults to using the GCC options '-mfpmath=sse' (if the
host system supports SSE2) or '-fno-tree-sra' (if not).  These GCC
options work around GCC bug 58416, which can cause Emacs to behave
incorrectly in rare cases.

---
** New configuration option '--disable-gc-mark-trace'.
This disables the GC mark trace buffer for about 5% better garbage
collection performance.  Doing so may make it more difficult for Emacs
developers to help finding GC-related bugs that you run into, which is
why the mark trace buffer is enabled by default.

\f
* Startup Changes in Emacs 31.1

** When run inside xterm, 'xterm-mouse-mode' is turned on by default.
This means that the mouse will work by default inside xterm terminals.
If your terminal does not behave properly with xterm mouse tracking
enabled, you can disable mouse tracking by putting '(xterm-mouse-mode
-1)' in your init file.

\f
* Changes in Emacs 31.1

** Etags

+++
*** New command-line options for handling unrecognized programming languages.
The new command-line option '--no-fallback-lang' disables attempts to
parse as Fortran or C/C++ files whose programming language 'etags' could
not determine.  This allows to avoid false positives and reduces the time
required to scan directories with many such files.  Another new option
'--no-empty-file-entries' disables generation of file entries in tags
tables for files in which no tags were found.

---
** find-func.el commands now have history enabled.
The 'find-function', 'find-library', 'find-face-definition', and
'find-variable' commands now allow retrieving previous input using the
usual minibuffer history commands.  Each command has a separate history.

Loading a Tree-Sitter mode (such as by using 'M-x load-library' or with
'M-x load-file') by default causes the corresponding non-Tree-Sitter
mode be remapped to the Tree-Sitter mode.  This remapping affects
visiting files for which 'auto-mode-alist' specifies a non-Tree-Sitter
mode, and also affects mode-specification cookies on the first line of a
file and mode specifications in file- and directory-local variables.  To
revert to using a non-Tree-Sitter mode, reload the corresponding mode
file anew.  To prevent file loading from turning on Tree-Sitter mode
when 'auto-mode-alist' or the file/directory-local variables specify a
non-Tree-Sitter mode, customize the user option 'major-mode-remap-alist'
to specify that a non-Tree-Sitter mode is "remapped" to itself.  For
example:

    (add-to-list 'major-mode-remap-alist '(c-mode))

specifies that C Mode should not be remapped to 'c-ts-mode' even if and
when 'c-ts-mode' is loaded.  Conversely,

    (add-to-list 'major-mode-remap-alist '(c-mode . c-ts-mode))

tells Emacs to always invoke 'c-ts-mode' whenever 'c-mode' is
requested, either by 'auto-mode-alist' or by file/directory-local
variables.

We recommend using 'major-mode-remap-alist' to express your preferences
for using Tree-Sitter or non-Tree-Sitter modes for files for which both
variants of major modes are available, because that variable overrides
the remapping Emacs might decide to perform as result of loading Lisp
files and features.

---
** New minor mode 'find-function-mode' replaces 'find-function-setup-keys'.

** Minibuffer and Completions

+++
*** New user option 'completion-eager-display'.
This option configures whether completion commands should display
the *Completions* buffer immediately.  When the variable is set to t all
completion commands show *Completions* immediately, respectively nil
disables the eager display for all commands.  The default setting auto
enables eager completion only if requested by the command.

+++
*** New user option 'completion-pcm-leading-wildcard'.
This option configures how the partial-completion style does completion.
It defaults to nil, which preserves the existing behavior.  When it is set
to t, the partial-completion style behaves more like the substring
style, in that a string being completed can match against a candidate
anywhere in the candidate string.

+++
*** 'completion-styles' now can contain lists of bindings.
In addition to being a symbol naming a completion style, an element of
'completion-styles' can now be a list of the form '(STYLE ((VARIABLE
VALUE) ...))' where STYLE is a symbol naming a completion style.
VARIABLE will be bound to VALUE (without evaluating it) while the style
is executing.  This allows multiple references to the same style with
different values for completion-affecting variables like
'completion-pcm-leading-wildcard' or 'completion-ignore-case'.  This also
applies for the styles configuration in 'completion-category-overrides'
and 'completion-category-defaults'.

---
*** Selected completion candidate is preserved across *Completions* updates.
When point is on a completion candidate in the *Completions* buffer
(because of 'minibuffer-next-completion' or for any other reason), point
will still be on that candidate after *Completions* is updated with a
new list of completions.  The candidate is automatically deselected when
the *Completions* buffer is hidden.

** Windows

+++
*** New hook 'window-deletable-functions'.
This abnormal hook gives its client a way to save a window from getting
deleted implicitly by functions like 'kill-buffer', 'bury-buffer' and
'quit-restore-window'.

+++
*** New user option 'kill-buffer-quit-windows'.
This option has 'kill-buffer' call 'quit-restore-window' to handle the
further destiny of any window showing the buffer to be killed.

+++
*** New window parameter 'quit-restore-prev'.
This parameter is set up by 'display-buffer' when it detects that the
window used already has a 'quit-restore' parameter.  Its presence gives
'quit-restore-window' a way to undo a sequence of buffer display
operations more intuitively.

+++
*** 'quit-restore-window' handles new values for BURY-OR-KILL argument.
The values 'killing' and 'burying' are like 'kill' and 'bury' but assume
that the actual killing or burying of the buffer is done by the caller.

+++
*** New user option 'quit-restore-window-no-switch'.
With this option set, 'quit-restore-window' will delete its window more
aggressively rather than switching to some other buffer in it.

---
*** The user option 'display-comint-buffer-action' has been removed.
It has been obsolete since Emacs 30.1.  Use '(category . comint)' instead.
Another user option 'display-tex-shell-buffer-action' has been removed too
for which you can use '(category . tex-shell)'.

** Frames

+++
*** New function 'frame-deletable-p'.
Calling this function before 'delete-frame' is useful to avoid that the
latter throws an error when the argument FRAME cannot be deleted.

** Tab Bars and Tab Lines

---
*** New abnormal hook 'tab-bar-auto-width-functions'.
This hook allows you to control which tab-bar tabs are auto-resized.

** Project

---
*** New command 'project-root-find-file'.
It is equivalent to running ‘project-any-command’ with ‘find-file’.

---
*** The MAYBE-PROMPT argument of 'project-current' can be a string.
When such value is used, the 'project-prompter' is called with it as the
first argument.  This is a way for the callers to indicate, for example,
the reason or the context why the project is asked for.

** Registers

*** New functions 'buffer-to-register' and 'file-to-register'.
These allow users to interactively store file and buffers in registers.
Killed buffers stored in a register using 'buffer-to-register' are
automatically converted to a file-query value if the buffer was visiting
a file.

** IDLWAVE has been moved to GNU ELPA.
The version bundled with Emacs is out-of-date, and is now marked as
obsolete.  Use 'M-x list-packages' to install the 'idlwave' package from
GNU ELPA instead.

+++
** New faces 'header-line-active' and 'header-line-inactive'.
These inherit from the 'header-line' face, but the faces actually used
on the header lines are now these two: the selected window uses
'header-line-active', non-selected windows use 'header-line-inactive'.

** In 'customize-face', the "Font family" attribute now supports completion.

\f
* Editing Changes in Emacs 31.1

** Commands for keyboard translation.
'key-translate' is now interactive.  It prompts for a key to translate
from, and another to translate to, and sets 'keyboard-translate-table'.
The new command 'key-translate-remove' prompts for a key/translation
pair with 'completing-read', and removes it from the translation table.

** Internationalization

---
*** Emacs now supports Unicode version 16.0.

---
*** New input method 'greek-polytonic'.
This input method has support for polytonic and archaic Greek
characters.

---
*** New language-environment and input method for Tifinagh.
The Tifinagh script is used to write the Berber languages.

---
*** New input methods for Northern Iroquoian languages.
Input methods are now implemented for Haudenosaunee languages in the
Northern Iroquoian language family: 'mohawk-postfix' (Mohawk
[Kanien’kéha / Onkwehonwehnéha]), 'oneida-postfix' (Oneida [Onʌyota:ká:
/ Ukwehuwehnéha]), 'cayuga-postfix' (Cayuga [Gayogo̱ho:nǫhnéha:ˀ]),
'onondaga-postfix' (Onondaga [Onųdaʔgegáʔ]), and 'seneca-postfix'
(Seneca [Onödowá’ga:’]).  Additionally, there is a general-purpose
'haudenosaunee-postfix' input method to facilitate writing in the
orthographies of the five languages simultaneously.

---
** 'visual-wrap-prefix-mode' now supports variable-pitch fonts.
When using 'visual-wrap-prefix-mode' in buffers with variable-pitch
fonts, the wrapped text will now be lined up correctly so that it's
exactly below the text after the prefix on the first line.

---
** New commands 'unix-word-rubout' and 'unix-filename-rubout'.
Unix-words are words separated by whitespace regardless of the buffer's
syntax table.  In a Unix terminal or shell, 'C-w' kills by Unix-word.
The new commands 'unix-word-rubout' and 'unix-filename-rubout' allow
you to bind keys to operate more similarly to the terminal.

---
** New user option 'kill-region-dwim'.
This option, if non-nil, modifies the fall-back behavior of
'kill-region' ('C-w') if no region is active, and will kill the last word
instead of raising an error.  Note that if you have disabled Transient
Mark mode you might prefer to use 'unix-word-rubout', as this feature
relies on there being an active region.

---
** New user option 'delete-pair-push-mark'.
This option, if non-nil, makes 'delete-pair' push a mark at the end of
the region enclosed by the deleted delimiters.  This makes it easy to
act on that region.  For example, we can highlight it using 'C-x C-x'.

+++
** Electric Pair mode can now pair multiple delimiters at once.
You can now insert or wrap text with multiple sets of parentheses and
other matching delimiters at once with Electric Pair mode, by providing
a prefix argument when inserting one of the delimiters.

+++
** You can now use 'M-~' during 'C-x s' ('save-some-buffers').
Typing 'M-~' while saving some buffers means not to save the buffer and
also to mark it as unmodified.  This is an alternative way to mark a
buffer as unmodified which doesn't require switching to that buffer.

** New minor mode 'delete-selection-local-mode'.
This mode sets 'delete-selection-mode' buffer-locally.  This can be
useful for enabling or disabling the features of 'delete-selection-mode'
based on the state of the buffer, such as for the different states of
modal editing packages.

\f
* Changes in Specialized Modes and Packages in Emacs 31.1

** Browse URL

*** New function 'browse-url-qutebrowser' for the Qutebrowser.
For better integration with the Qutebrowser, set
'browse-url(-secondary)-browser-function' to 'browse-url-qutebrowser'.

** CL-Lib
+++
*** 'cl-labels' now also accepts (FUNC EXP) bindings, like 'cl-flet'.
Such bindings make it possible to compute which function to bind to FUNC.

** Whitespace

---
*** 'whitespace-cleanup' now adds missing newline at end of file.
If 'whitespace-style' includes 'missing-newline-at-eof' (which is the
default), the 'whitespace-cleanup' function will now add the newline.

** Gnus

---
*** Replying to icalendar events now supports specifying a comment.
When called with a prefix argument, accepting, declining, or tentatively
accepting an icalendar event will prompt for a comment to add to the
response.

** Button

+++
*** New function 'unbuttonize-region'.
It removes all the buttons in the specified region.

+++
*** Disabling 'button-mode' now removes all buttons in the current buffer.

** Eshell

---
*** New interactive command 'eshell-clear'.
This command scrolls the screen so that only the current prompt is
visible, optionally erasing all the previous input/output as well.
Previously, the Eshell built-in command 'eshell/clear' supported this
(e.g., to call it via 'M-x'), but this new command behaves more
consistently if you have a partially-typed command at the Eshell prompt.

---
*** New user option 'eshell-command-async-buffer'.
This option lets you tell 'eshell-command' how to respond if its output
buffer is already in use by another invocation of 'eshell-command', much
like 'async-shell-command-buffer' does for 'shell-command'.  By default,
this will prompt for confirmation before creating a new buffer when
necessary.  To restore the previous behavior, set this option to
'confirm-kill-process'.

+++
*** 'eshell-execute-file' is now an interactive command.
Interactively, this now prompts for a script file to execute.  With the
prefix argument, it will also insert any output into the current buffer
at point.

+++
*** 'eshell-command' and 'eshell-execute-file' can now set where stderr goes.
These functions now take an optional ERROR-TARGET argument to control
where to send the standard error output.  See the "(eshell) Entry
Points" node in the Eshell manual for more details.

+++
*** You can now loop over ranges of integers with the Eshell 'for' command.
When passing a range like 'BEGIN..END' to the Eshell 'for' command,
Eshell will now iterate over each integer between BEGIN and END, not
including END.

+++
*** Conditional statements in Eshell now use an 'else' keyword.
Eshell now prefers the following form when writing conditionals:

    if {conditional} {true-subcommand} else {false-subcommand}

The old form (without the 'else' keyword) is retained for compatibility.

+++
*** You can now chain conditional statements in Eshell.
When using the newly-preferred conditional form in Eshell, you can now
chain together multiple 'if'/'else' statements.  For more information,
see "(eshell) Control Flow" in the Eshell manual.

+++
*** Eshell's built-in 'wait' command now accepts a timeout.
By passing '-t' or '--timeout', you can specify a maximum time to wait
for the processes to exit.  Additionally, you can now wait for external
processes by passing their PIDs.

---
*** New hook 'eshell-after-initialize-hook'.
This hook runs after an Eshell session has been fully initialized,
immediately before running 'eshell-post-command-hook' for the first
time.

+++
*** Improved history Isearch.
History Isearch in Eshell is reworked.  Two new commands
'eshell-isearch-backward-regexp' and 'eshell-isearch-forward-regexp' are
added for incrementally searching through the input history.
'eshell-isearch-backward-regexp' is bound to 'M-r' by default, and 'M-s'
is freed for normal search commands.  If you would like to restore the
previous key-bindings for the non-incremental search commands, put in
your configuration:

    (keymap-set eshell-hist-mode-map "M-r"
                #'eshell-previous-matching-input)
    (keymap-set eshell-hist-mode-map "M-s"
                #'eshell-next-matching-input)

+++
*** New user option 'eshell-history-isearch'
When 'eshell-history-isearch' is nil (the default), Isearch commands
search in the buffer contents.  If you customize it to t, those commands
only search in input history.  If you customize it to the symbol 'dwim',
those commands search in input history only when the point is after the
last prompt.

** SHR

+++
*** SHR now slices large images into rows.
Sliced images allow for more intuitive scrolling up/down by letting you
scroll past each slice, instead of jumping past the entire image.
Previously, SHR sliced images when zoomed to their original size, no
matter how large or small that was.  Now, SHR slices any images taller
than 'shr-sliced-image-height'.  For more information, see the "(eww)
Advanced" node in the EWW manual.

---
*** You can now customize the image zoom levels to cycle through.
By customizing 'shr-image-zoom-levels', you can change the list of zoom
levels that SHR cycles through when calling 'shr-zoom-image'.

---
*** New user option 'shr-fill-text'.
When 'shr-fill-text' is non-nil (the default), SHR will fill text
according to the width of the window.  If you customize it to nil, SHR
will leave the text as-is; in that case, EWW will automatically enable
'visual-line-mode' when displaying a page so that long lines are
visually wrapped at word boundaries.

** EWW

---
*** EWW now enables 'visual-wrap-prefix-mode' when 'shr-fill-text' is nil.
By default, 'shr-fill-text' is t, and EWW fills the text according to
the width of the window.  If you customize 'shr-fill-text' to nil, EWW
will now automatically turn on 'visual-wrap-prefix-mode' in addition to
'visual-line-mode', so that long lines are wrapped at word boundaries
near window edge and the continuation lines are indented using prefixes
computed from surrounding context.

---
*** New user option 'eww-guess-content-type-functions'.
The value is a list of functions that EWW should call to determine the
content-type of Web pages which don't have a valid 'Content-Type'
header.  The default value is a function that considers a page with an
HTML 'doctype' declaration to have context-type "text/html".

** CC mode

+++
*** New type of 'c-offsets-alist' element.
The 'cdr' of such an alist element may now be a syntactic symbol.  A
source line with a syntactic element whose symbol is the 'car' of that
alist element is indented as though it were the 'cdr'.

+++
*** Enums now have their own syntactic symbols.
The new symbols 'enum-open', 'enum-close', 'enum-intro' and
'enum-entry' are used in the analysis of enum constructs.  Previously
they were given 'brace-list-open', etc.  These are fully described in
the "(ccmode) Enum Symbols" node of the CC mode manual.

+++
*** Enums are now, by default, indented like classes, not brace-lists.
To get the old behavior back, add an element '(enum-open
. brace-list-open)' to 'c-offsets-alist' in your CC mode style, or amend
'c-offsets-alist' likewise in any of the other ways detailed in the
"(ccmode) Config Basics" node of the CC mode manual.

** Go-ts mode

+++
*** New unit test commands.
Three new commands are now available to run unit tests.

The 'go-ts-mode-test-function-at-point' command runs the unit test at
point.  If a region is active, it runs all the unit tests under the
region.  It is bound to 'C-c C-t t' in 'go-ts-mode'.

The 'go-ts-mode-test-this-file' command runs all unit tests in the current
file.  It is bound to 'C-c C-t f' in 'go-ts-mode'.

The 'go-ts-mode-test-this-package' command runs all unit tests under the
package of the current buffer.  It is bound to 'C-c C-t p' in 'go-ts-mode'.

The 'go-ts-mode-build-tags' user option is available to set a list of
build tags for the test commands.

** C-ts mode

+++
*** New user option 'c-ts-mode-enable-doxygen'.
By default, this is nil, and the Doxygen comment blocks in C/C++ source
are highlighted like other comments.  When non-nil, Doxygen comment
blocks are syntax-highlighted if the Doxygen grammar library is
available.

** Java-ts mode

+++
*** New user option 'java-ts-mode-enable-doxygen'.
By default, this is nil, and the Doxygen comment blocks in Java source
are highlighted like other comments.  When non-nil, Doxygen comment
blocks are syntax-highlighted if the Doxygen grammar library is
available.

** Emacs Lisp mode

---
*** Checkdoc no longer warns about missing footer lines in some cases.
Emacs Lisp libraries have traditionally ended with a footer line
(sometimes referred to as "terminating comment").  Their purpose was to
easily detect files that had been truncated in transit on ancient and
less reliable connections:

    ;; some-cool-package.el ends here

'checkdoc' will no longer warn if that line is missing for packages that
explicitly only support Emacs 30.1 or later, as specified in the
"Package-Requires" header.  The reason for keeping the warning for
packages that support earlier versions of Emacs is that package.el in
those versions can't install packages where that line is missing.

This change affects both 'M-x checkdoc' and the corresponding flymake
backend.

---
*** Checkdoc will now flag incorrect formatting in warnings.
This affects calls to 'warn', 'lwarn', 'display-warning', and
'message-box'.

---
*** The default of 'checkdoc-verb-check-experimental-flag' is now nil.
In most cases, having it enabled leads to a large amount of false
positives.

** DocView

---
*** Dedicated buffer for plain text contents.
When switching to the plain text contents with 'doc-view-open-text',
DocView now creates a dedicated buffer to display it.  'C-c C-c' gets you
back to real DocView buffer if it still exists.

+++
*** New commands to save and restore pages in buffer-local registers.
Docview can store the current page to buffer-local registers with the new
command 'doc-view-page-to-register' (bound to 'm'), and later the stored
page can be restored with 'doc-view-jump-to-register' (bound to ''').

+++
*** Docview can generate imenu indices for DjVu and ODF documents.
When the 'djvused' program is available, Docview can now generate an imenu
index for DjVu files from its outline.  Indices for Open Document Format
(ODF) files as used by OpenOffice and LibreOffice are generated using
the 'mutool' program after their initial conversion to PDF format.  The
name of the 'djvused' program can be customized by changing the user
option 'doc-view-djvused-program'.

** Flyspell

---
*** New user option 'flyspell-delay-use-timer'.
By default, Flyspell waits after so-called "delayed" commands by calling
'sit-for'.  If you customize this option to non-nil, Flyspell instead
sets up a timer to perform spell-checking after a short delay, which
allows idle timers and other code to run during this delay period.  We
consider making this behavior the default in a future Emacs version, so
we invite Flyspell users to enable this new option and report issues.

** Tramp

+++
*** Connection method "kubernetes" supports now optional namespace.
The host name for Kubernetes connections can be of kind
[CONTAINER.]POD[%NAMESPACE], in order to specify the namespace to be
used.  This overrides the setting in 'tramp-kubernetes-namespace', if
any.

+++
*** Different proxies for the same destination host name can be specified.
A typical example are docker containers, which run on different hosts
under the same docker name.  When the user option
'tramp-show-ad-hoc-proxies' is non-nil, such ad-hoc multi-hop file names
can be used in parallel.  Example: on both remote hosts "host1" and
"host2" there is a docker container "name", respectively:

    /ssh:user1@host1|docker:name:
    /ssh:user2@host2|docker:name:

This feature is experimental.

** Diff

---
*** New command 'diff-kill-ring-save'.
This command copies to the 'kill-ring' a region of text modified
according to diffs in the current buffer, but without applying the diffs
to the original text.  If the selected range extends a hunk, the
command attempts to look up and copy the text in-between the hunks.

+++
*** New command 'diff-revert-and-kill-hunk' bound to 'C-c M-r'.
This command reverts the hunk at point (i.e., applies the reverse of the
hunk), and then removes the hunk from the diffs.
This is useful to undo or revert changes, committed and uncommitted, when
you are in buffers generated by 'C-x v =' and 'C-x v D'.

---
*** 'diff-file-prev' and 'diff-hunk-prev' always move to start of header.
Previously, 'diff-file-prev' and 'diff-hunk-prev' would move when point
is after the corresponding file or hunk header, but not when inside it.
Now they will always move to the start of the current header.

+++
*** New command 'diff-delete-other-hunks' bound to 'C-c RET n'.
This command deletes all hunks other than the current hunk.  It is
useful to prepare a "*vc-diff*" buffer for committing a single hunk.
When the region is active, it deletes all hunks that the region does not
overlap.

*** 'diff-apply-hunk' now supports creating and deleting files.

---
*** 'vc-version-diff' and 'vc-root-version-diff' changed default for REV1.
They suggest the previous revision as the default for REV1, not the last
one as before.  This makes them different from 'vc-diff' and
'vc-root-diff' when those are called without a prefix argument.

** PHP-ts mode

---
*** 'php-ts-mode-run-php-webserver' can now accept a custom "php.ini" file.
You can use the new optional argument CONFIG when calling
'php-ts-mode-run-php-webserver' to pass an alternative "php.ini" file to
the built-in Web server.  Interactively, when invoked with a prefix
argument, 'php-ts-mode-run-php-webserver' prompts for the config file as
well as for other connection parameters.

** Rust-ts mode

---
*** New user option 'rust-ts-mode-fontify-number-suffix-as-type'.
Rust number literals may have an optional type suffix.  When this option
is non-nil, this suffix is fontified using 'font-lock-type-face'.

** Ediff

+++
*** Ediff's copy commands now apply to all changes with 'C-u' prefix.
The Ediff copy commands, bound to 'a', 'b', 'ab', etc., now copy all
changes when supplied with a universal prefix argument via 'C-u':

- 'C-u a' copies all changes from buffer A to buffer B (in 2-way diff)
  or to buffer C (in 3-way diff or merge).
- 'C-u b' copies all changes from buffer B to buffer A (in 2-way diff)
  or to buffer C (in 3-way diff or merge).
- 'C-u a b' copies all changes from buffer A to buffer B.
- 'C-u b a' copies all changes from buffer B to buffer A.
- 'C-u a c' copies all changes from buffer A to buffer C.
- 'C-u b c' copies all changes from buffer B to buffer C.
- 'C-u c a' copies all changes from buffer C to buffer A.
- 'C-u c b' copies all changes from buffer C to buffer B.

** Dired

+++
*** New user option 'dired-check-symlinks' allows disabling validity checks.
Dired uses 'file-truename' to check symbolic link validity when
fontifying them, which can be slow for remote directories.  Setting
'dired-check-symlinks' to nil disables these checks.  Defaults to t, can
be set as a connection-local variable.

---
*** New user option 'dired-hide-details-hide-absolute-location'.
When Dired's 'dired-hide-details-mode' is enabled, also hide the
'default-directory' absolute location, typically displayed as the first
line in a Dired buffer.

With 'dired-hide-details-hide-absolute-location':

    project: (100 GiB available)

Without 'dired-hide-details-hide-absolute-location':

    /absolute/path/to/my/important/project: (100 GiB available)

---
*** Clicking on base name of directory reverts buffer.
When 'dired-make-directory-clickable' is non-nil, clicking on the base
name of the directory now reverts the Dired buffer.

** Grep

+++
*** Grep results can be edited to reflect changes in the originating file.
Like Occur Edit mode, typing 'e' in the "*grep*" buffer will now make
the 'grep' results editable.  The edits will be reflected in the buffer
visiting the originating file.  Typing 'C-c C-c' will leave the Grep
Edit mode.

** TeX modes

+++
*** New Xref backend for TeX modes.
The new backend ('tex-etags') is on by default, and improves the
functionality of the standard 'xref' commands in TeX buffers.  You can
restore the standard 'etags' backend with the 'M-x xref-etags-mode'
toggle.

** BibTeX mode

---
*** New user option 'bibtex-entry-ask-for-key'.
When enabled, 'bibtex-entry' asks for a key.

** Midnight mode

---
*** Change for activating the mode.
Putting '(require 'midnight)' in your init file no longer activates the
mode.  Now, one needs to say '(midnight-mode +1)' instead.

** Python mode

---
*** Prefer "python" for 'python-interpreter' and 'python-shell-interpreter'.
On recent versions of mainstream GNU/Linux distributions, "python"
either does not exist or it points to Python 3.  These user options now
default to using "python", falling back to "python3" if it does not
exist.  If "python" points to Python 2 on your system, you now have to
customize these variables to "python3" if you want to use Python 3
instead.

---
*** Support of 'electric-layout-mode' added.

** Tmm Menubar

---
*** A new shortcut to navigate to previous menu.
The hardcoded '^' shortcut gets you back to the previous menu.

---
*** New user option 'tmm-shortcut-inside-entry'.
When non-nil, highlight the character shortcut in the menu entry's
string instead of preprending it and 'tmm-mid-prompt' to said entry.

** Foldout

---
*** New command 'foldout-widen-to-current-fold'.
This command widens the view to the current fold level when in a fold,
or behaves like 'widen' if not in a fold.

** MPC

---
*** New user option 'mpc-notifications'.
When non-nil, MPC (the Emacs front-end to Music Player Daemon) displays
a desktop notification when the song changes, using
'notifications-notify'.  The notification's title and body can be
customized using the new user options 'mpc-notifications-title' and
'mpc-notifications-body'.

---
*** New user option 'mpc-crossfade-time'.
When non-nil, MPC will crossfade between songs for the specified number
of seconds.  Crossfading can be toggled using the command
'mpc-toggle-crossfade' or from the MPC menu.

---
*** New command 'mpc-describe-song'.
This command displays information about the currently playing song or
song at point in the MPC-Songs buffer.  The list of tags to display can
be customized using the new user option 'mpc-song-viewer-tags' and the
appearance of the list with the new faces 'mpc-song-viewer-tag',
'mpc-song-viewer-value', and 'mpc-song-viewer-empty'.

** VC

---
*** Using 'e' from Log View mode to modify change comments now works for Git.

---
*** New user option 'vc-allow-rewriting-published-history'.
Some VCS commands can change your copy of published change history
without warning.  In VC we try to detect before that happens, and stop.
You can customize this option to permit rewriting history even though
Emacs thinks it is dangerous.

---
*** 'vc-clone' is now an interactive command.
When called interactively, 'vc-clone' now prompts for the remote
repository address, and the directory into which to clone the
repository.  It tries to automatically determine the VC backend for
cloning, or prompts for that, too.

---
*** 'vc-clone' now accepts an optional argument OPEN-DIR.
When the argument is non-nil, the function switches to a buffer visiting
the directory into which the repository was cloned.

** Package

---
*** New optional argument to 'package-autoremove'.
An optional argument NOCONFIRM has been added to 'package-autoremove'.
If it is non-nil, or when invoked with a prefix argument,
'package-autoremove' will not prompt the user for confirmation before
removing packages.

---
*** New prefix argument for 'package-install-selected-packages'.
When invoked with a prefix argument, 'package-install-selected-packages'
will not prompt the user for confirmation before installing packages.

** Xref

---
*** Xref commands that jump to some location use 'display-buffer'.
The commands that jump to some location use 'display-buffer' and specify
the category 'xref-jump'.  As a result, you can customize how the
destination window is chosen using 'display-buffer-alist'.  Example:

  (setq display-buffer-alist '(((category . xref-jump)
                                (display-buffer-reuse-window
                                 display-buffer-use-some-window)
                                (some-window . mru))))

\f
* New Modes and Packages in Emacs 31.1

\f
* Incompatible Lisp Changes in Emacs 31.1

** Nested backquotes are not supported any more in Pcase patterns.

** The 'rx' category name 'chinese-two-byte' must now be spelled correctly.
An old alternative name (without the first 'e') has been removed.

---
** All the digit characters now have the 'digit' category.
All the characters whose Unicode general-category is Nd now have the
'digit' category, whose mnemonic is '6'.  This includes both ASCII and
non-ASCII digit characters.

---
** All the symbol characters now have the 'symbol' category.
All the characters that belong to the 'symbol' script (according to
'char-script-table') now have the 'symbol' category, whose mnemonic is
'5'.

** Some libraries obsolete since Emacs 24.4 and 24.5 have been removed:
cc-compat.el, info-edit.el, meese.el, otodo-mode.el, rcompile.el,
sup-mouse.el, terminal.el, vi.el, vip.el, ws-mode.el, and yow.el.

+++
** 'if-let' and 'when-let' are now obsolete.
Use 'if-let*', 'when-let*' and 'and-let*' instead.

This effectively obsoletes the old '(if-let (SYMBOL SOMETHING) ...)'
single binding syntax, which we'd kept only for backwards compatibility.

---
** The Eshell 'pwd' command now expands the directory name on all systems.
This ensures that user directories are properly expanded to their full
name.  Previously, Eshell only did this for MS-Windows systems. To
restore the old behavior, you can set 'eshell-pwd-convert-function' to
'identity'.

\f
* Lisp Changes in Emacs 31.1

---
** New function 'native-compile-directory'.
This function natively-compiles all Lisp files in a directory and in its
sub-directories, recursively, which were not already natively-compiled.

---
** New function 'color-blend'.
This function takes two RGB lists and optional ALPHA and returns an RGB
list whose elements are blended in linear space proportional to ALPHA.

+++
** The 'defcustom' ':local' keyword can now be 'permanent-only'.
This means that the variable's 'permanent-local' property is set to t,
without marking it as automatically buffer-local.

---
** The obsolete face attribute ':reverse-video' has been removed.
Use ':inverse-video' instead.

+++
** Support interactive D-Bus authorization.
A new ':authorizable t' parameter has been added to 'dbus-call-method'
and 'dbus-call-method-asynchronously' to allow the user to interactively
authorize the invoked D-Bus method (for example via polkit).

** The customization group 'wp' has been removed.
It has been obsolete since Emacs 26.1.  Use the group 'text' instead.

** Tree-sitter changes

+++
*** Indirect buffers can have their own parser list.
Before, indirect buffers share their base buffer’s parser list and
parsers.  Now they can have their own parser list.

+++
*** New variable 'treesit-language-remap-alist'.
This variable allows a user to remap one language into another, such
that creating a parser for language A actually creates a parser for
language B.  By extension, any font-lock rules or indentation rules for
language A will be applied to language B instead.

This is useful for reusing font-lock rules and indentation rules of
language A for language B, when language B is a strict superset of
language A.

+++
*** New accessor functions for each setting in 'treesit-font-lock-settings'.
Now users can access a setting's query, feature, enable flag, and
override flag by 'treesit-font-lock-setting-query',
'treesit-font-lock-setting-feature', 'treesit-font-lock-setting-enable',
and 'treesit-font-lock-setting-override'.

+++
** New optional BUFFER argument for 'string-pixel-width'.
If supplied, 'string-pixel-width' will use any face remappings from
BUFFER when computing the string's width.

---
** New macro 'with-work-buffer'.
This macro is similar to the already existing macro 'with-temp-buffer',
except that it does not allocate a new temporary buffer on each call,
but tries to reuse those previously allocated (up to a number defined by
the new variable 'work-buffer-limit', which defaults to 10).

+++
** 'date-to-time' now defaults to local time.
The function now assumes local time instead of Universal Time when
its argument lacks explicit time zone information.  This has been the
de-facto behavior since Emacs 24 although documentation said otherwise.
Also, the fallback on 'timezone-make-date-arpa-standard' has been
removed because its supported date styles can be handled by
'parse-time-string'.  To restore the previously documented behavior,
specify "+0000" or "Z" as the time zone in the argument.

---
** The 'min-width' property is now supported for overlays as well.
This 'display' property was previously supported only as text property.
Now overlays can also have this property, with the same effect for the
text "covered" by the overlay.

+++
** New macro 'cond*'.
The new macro 'cond*' is an alternative to 'cond' and 'pcase'.
Like them, it can be used to define several clauses, each one with its
own condition; the first clause that matches will cause its body to be
evaluated.
'cond*' can use Pcase's pattern matching syntax and also provides
another pattern matching syntax that is different from that of 'pcase',
which some users might find less cryptic.
See the Info node "(elisp) cond* Macro" for details.

---
** New function 'shell-command-do-open'.
This lets a Lisp program access the core functionality of the
'dired-do-open' command.  It opens a file or files using an external
program, choosing the program according to the operating system's
conventions.

+++
** 'make-vtable' can create an empty vtable.
It is now possible to create a vtable without data, by leaving the
':objects' list empty, or by providing a ':objects-function' that
(initially) produces no data.  In such a case, it is necessary to
provide a ':columns' spec, so that the number of columns and their
widths can be determined.  Columns widths can be set explicitly, or they
will be calculated based on the window width.

+++
** New symbol property 'repeat-continue-only' for 'repeat-mode'.
A command with this symbol property whose value is a list of repeat
maps will not activate the repeat map in 'repeat-mode'.  It will only
continue the already activated repeating sequence.  Also 'defvar-keymap'
supports a new keyword ':continue-only' with a list of commands that
only continue the active repeating sequence.

\f
* Changes in Emacs 31.1 on Non-Free Operating Systems

---
** Process execution has been optimized on Android.
The run-time performance of subprocesses on recent Android releases,
where a userspace executable loader is required, has been optimized on
systems featuring Linux 3.5.0 and above.

---
** 'NSSpeechRecognitionUsageDescription' now included in "Info.plist" (macOS).
Should Emacs (or any built-in shell) invoke a process using macOS speech
recognition APIs, the relevant permission dialog is now displayed, thus
allowing Emacs users access to speech recognition utilities.

Note: Accepting this permission allows the use of system APIs, which may
send user data to Apple’s speech recognition servers.

---
** Emacs on MS-Windows now supports GUI dialogs and message boxes better.
In particular, it is now possible to show text with embedded newlines in
a dialog popped by 'message-box'.  This is supported on Windows Vista
and later versions.

---
** Emacs on MS-Windows now supports drag-n-drop of text into a buffer.
This is in addition to drag-n-drop of files, that was already
supported.  As on X, the user options 'dnd-scroll-margin' and
'dnd-indicate-insertion-point' can be used to customize the process.

---
** Emacs on MS-Windows now supports color fonts.
On Windows 8.1 and later versions Emacs now uses DirectWrite to draw
text, which supports color fonts.  This can be disabled by setting the
variable 'w32-inhibit-dwrite' to t.  Also see 'w32-dwrite-available' and
'w32-dwrite-reinit' to check availability and to configure the
DirectWrite rendering parameters.

To show color Emojis in Emacs, customize the default fontset to use a
color Emoji font installed on your system for the 'emoji' script.

+++
** Emacs on MS-Windows now supports 'yank-media'.
This command inserts clipboard data of different formats into the
current buffer, if the major mode supports it.  (Support for
'yank-media' will be unavailable on MS-Windows if Emacs was configured
'--without-native-image-api'.)

---
** Images on MS-Windows now support the ':transform-smoothing' flag.
Transformed images are smoothed using the bilinear interpolation by
means of the GDI+ library.

---
** Emacs on MS-Windows now supports the ':data' keyword for 'play-sound'.
In addition to ':file FILE' for playing a sound from a file, ':data
DATA' can now be used to play a sound from memory.

\f
----------------------------------------------------------------------
This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

\f
Local variables:
coding: utf-8
mode: outline
mode: emacs-news
paragraph-separate: "[	 \f]"
end: