Add the variable `fill-region-as-paragraph-function' to provide
a way to override how functions like `fill-region' fill text.
* doc/lispref/text.texi (Filling): Document
`fill-region-as-paragraph-function' variable.
* doc/emacs/text.texi (Fill Commands): Reference
`fill-region-as-paragraph-function' variable.
* lisp/textmodes/fill.el (fill-region-as-paragraph-function):
Add variable.
(fill-region-as-paragraph): Convert into
`fill-region-as-paragraph-function' wrapper.
(fill-region-as-paragraph-default): Rename old
`fill-region-as-paragraph' function.
(fill-region-as-paragraph-semlf): Update calls to
`fill-region-as-paragraph-default'.
(fill-region): Add reference to `fill-region-as-paragraph-function'
in doc string.
* test/lisp/textmodes/fill-tests.el (fill-test-fill-region): Add
test case for the `fill-region' function.
* test/lisp/textmodes/fill-resources/fill-region.erts: Add test
data.  (Bug#78816)

print_error_message can throw after producing some output, so use
unwind-protect to ensure prin1-to-string-buffer is cleared.

* src/print.c (erase_prin1_to_string_buffer): New.
(Ferror_message_string): Use it to catch errors thrown in
'print_error_message'.
* test/src/print-tests.el (error-message-string-circular): Expand
test.

This reverts commit a4ec9ca12969018cdf15b8cc713b3ba054326f99.
It caused unnecessary errors, see bug#78593.

* lisp/progmodes/peg.el (peg-parse): Be more careful when
testing if a symbol is the name of an existing rule.  Improve docstring.

test/lisp/progmodes/peg-tests.el (peg-tests--peg-parse): New test.

* src/fileio.c (Finsert_file_contents): Inhibit ask-supersession
only if we're VISITing in a non-narrowed buffer (bug#78866).

* test/src/fileio-tests.el (ert--tests-dir): New var.
(fileio-tests--insert-file-contents-supersession): New test.

* lisp/net/eww.el (eww--walk-readability, eww-readable-dom): New
functions.
(eww-display-html): Call 'eww-readable-dom'.
(eww-readable): Call 'eww-readable-dom'.  Don't copy over 'eww-data'
properties that our new readable page can handle on its own.
(eww-score-readability): Rewrite in terms of 'eww--walk-readability'.
Make obsolete.
(eww-highest-readability): Make obsolete.

* test/lisp/net/eww-tests.el (eww-test--lots-of-words)
(eww-test--wordy-page): New variables...
(eww-test/readable/toggle-display): ... use them.
(eww-test/readable/default-readable): Make sure that the readable page
includes the <title> and <link> tags (bug#77299).

* test/src/treesit-tests.el (treesit--ert-test-defun-navigation):
Replace 'treesit-defun-type-regexp' with
'(or treesit-defun-type-regexp 'defun)' that fixes the tests
for ts-modes that set up the 'defun' thing instead of
'treesit-defun-type-regexp'.

This add support for insert string pairs in 'electric-pairs-mode'.
* lisp/elec-pair.el (electric-pair-pairs)
(electric-pair-text-pairs): Add new defcustom types.
(electric-pair-syntax-info)
(electric-pair-post-self-insert-function): Add support for
strings.

* etc/NEWS: Announce changes.

* test/lisp/electric-tests.el: Add new tests.