* test/src/buffer-tests.el (buffer-tests-buffer-local-variables-undo):
New.

From a patch privately suggested by Mattias Engdegård on 2020-05-11
in a followup to Bug#40671.
* admin/charsets/cp51932.awk:
* admin/charsets/eucjp-ms.awk:
Generate code that does not modify constant conses.
* doc/misc/emacs-mime.texi (Encoding Customization):
* lisp/emacs-lisp/byte-opt.el (byte-compile-side-effect-free-ops):
* lisp/frameset.el (frameset-persistent-filter-alist):
* lisp/gnus/gnus-sum.el (gnus-article-mode-line-format-alist):
Use append instead of nconc.
* lisp/language/japanese.el (japanese-ucs-cp932-to-jis-map)
(jisx0213-to-unicode):
Use mapcar instead of mapc.
* lisp/language/lao-util.el (lao-transcription-consonant-alist)
(lao-transcription-vowel-alist):
* lisp/language/tibetan.el (tibetan-subjoined-transcription-alist):
Use copy-sequence.
* test/src/fns-tests.el (fns-tests-nreverse):
(fns-tests-sort, fns-tests-collate-sort)
(fns-tests-string-version-lessp, fns-tests-mapcan):
Use copy-sequence, vector, and list.

* test/src/charset-tests.el:
* test/src/chartab-tests.el:
* test/src/cmds-tests.el:
* test/src/coding-tests.el (top-level)
(generate-ascii-file, generate-mostly-nonascii-file):
* test/src/doc-tests.el:
* test/src/floatfns-tests.el:
* test/src/font-tests.el:
* test/src/keymap-tests.el:
* test/src/process-tests.el (top-level)
(process-test-sentinel-wait-function-working-p)
(process-test-stderr-buffer, process-test-stderr-filter):
* test/src/textprop-tests.el:
* test/src/thread-tests.el:
* test/src/timefns-tests.el:
* test/src/undo-tests.el:
* test/src/xml-tests.el: Use lexical-binding.

* src/character.h (MULTIBYTE_LENGTH, MULTIBYTE_LENGTH_NO_CHECK):
Remove, replacing with ...
(multibyte_length): ... this new function.  All callers changed.
The new function rejects overlong multibyte forms.
* test/src/buffer-tests.el (buffer-multibyte-overlong-sequences):
New test.

05089a4d65 (origin/emacs-27) Tweak wording re constant variables
a1040861f1 Tweak setcar-related wording
751510f865 * lisp/image-mode.el: Add prefix key 's' and reduce depend...
9261a219ec * doc/emacs/windows.texi (Window Convenience): Decribe mor...
e1d42da0d6 Fix mutability glitches reported by Drew Adams
5805df74f5 Improve mutability doc
dca35b31d0 Improve mutability documentation
81e7d7f111 Document that quoting yields constants
5734339f40 * doc/lispref/keymaps.texi (Extended Menu Items, Easy Menu...
14a570afae Remove #' and function quoting from lambda forms in manual
d5ec18c66b * src/regex-emacs.c (re_match_2_internal): Rework comment ...
4df8a61117 Add new node "Image Mode" to Emacs Manual.
d7d5ee6c57 ; Fix a typo in cmdargs.texi (bug#40701)
5e9db48fbe * doc/lispref/display.texi (Customizing Bitmaps): Fix typo.
eebfb72c90 Document constant vs mutable objects better
6c187ed6b0 Improve documentation of 'sort-lines'
52288f4b66 Mention 'spam-stat-process-directory-age' in the documenta...
067b070598 ; Fix some typos and doc issues (bug#40695)

# Conflicts:
#	etc/NEWS

* src/callproc.c (Fcall_process_region): Fix behavior when START is
nil and DELETE is non-nil.

* test/src/callproc-tests.el
(call-process-region-entire-buffer-with-delete): New unit test.

Spotted by Kazuhiro Ito.

* src/coding.c (code_convert_string):
Set Vlast_coding_system if appropriate.
* test/src/coding-tests.el (coding-nocopy-ascii): Add test.

To sidestep conversion altogether when EOL conversion applies, we must
either be encoding a string without NL, or decoding without CR.

* src/coding.c (string_ascii_p): Revert to a pure predicate.
(code_convert_string): Fix logic.  Don't use uninitialised
ascii_p (removed).  Use memchr to detect CR or LF in string when needed.
* test/src/coding-tests.el (coding-nocopy-ascii):
Update tests to include encodings with explicit EOL conversions.