* lisp/language/japan-util.el (<toplevel>): Use `pcase-dolist` and `when`.
(japanese-string-conversion): Use `point-min`.

* lisp/language/japan-util.el (japanese-replace-region): Allow
STRING to be a character in addition  to a string.  Un-obsolete
it.
(japanese-katakana-region, japanese-hiragana-region)
(japanese-hankaku-region, japanese-zenkaku-region): Call
'japanese-replace-region' instead of 'replace-region-contents'.
(Bug#77397)

* lisp/minibuffer.el (completion--replace):
* lisp/emacs-lisp/cl-lib.el (cl--set-buffer-substring):
* lisp/subr.el (replace-string-in-region):
Use `replace-region-contents` instead of insert+delete.

* lisp/help-fns.el (help-fns--signature):
Use `replace-region-contents` instead of `cl--set-buffer-substring`.

* lisp/language/japan-util.el (japanese-replace-region):
Rewrite using `replace-region-contents` and mark obsolete.
(japanese-katakana-region, japanese-hankaku-region):
Use `replace-region-contents` instead.

* lisp/progmodes/flymake-proc.el (flymake-proc--replace-region):
Rewrite using `replace-region-contents` and mark obsolete.
(flymake-proc--check-patch-master-file-buffer):
Use `replace-region-contents` instead.

* lisp/textmodes/string-edit.el (read-string-from-buffer):
* lisp/simple.el (read-from-kill-ring, read-shell-command)
(read-signal-name):
* lisp/replace.el (read-regexp-case-fold-search):
* lisp/auth-source.el (read-passwd):
* lisp/subr.el (read-key, read-number):
* lisp/minibuffer.el (read-file-name, read-no-blanks-input):
* lisp/international/mule-cmds.el (read-multilingual-string):
* lisp/language/japan-util.el (read-hiragana-string):
* lisp/files-x.el (read-file-local-variable)
(read-file-local-variable-mode, read-file-local-variable-value):
* lisp/faces.el (read-face-font, read-face-name):
* lisp/simple.el (read-extended-command):
* lisp/env.el (read-envvar-name):
* lisp/files.el (read-directory-name):
* lisp/faces.el (read-color):
* lisp/international/mule-diag.el (read-charset):
* lisp/emacs-lisp/map-ynp.el (read-answer):
* src/coding.c (Fread_coding_system)
(Fread_non_nil_coding_system):
* src/minibuf.c (Fread_command, Fread_from_minibuffer):
* src/lread.c (Fread_char, Fread_char_exclusive, Fread_event): Doc
fixes.

Run "TZ=UTC0 admin/update-copyright".

* lisp/language/japan-util.el
(setup-japanese-environment-internal): Prefer UTF-8 for Cygwin and
other Posix hosts; prefer Codepage 932 on DOS/Windows.  (Bug#69493)