Modularize add-log-current-defun.

Suggested by Jari Aalto.

* lisp/emacs-lisp/lisp-mode.el (lisp-current-defun-name): New.
(lisp-mode-variables): Use it.

* lisp/progmodes/cc-mode.el (c-common-init):
* lisp/progmodes/cperl-mode.el (cperl-mode): Set a value for
add-log-current-defun-function.

* lisp/progmodes/m4-mode.el (m4-current-defun-name): New function.
(m4-mode): Use it.

* lisp/progmodes/perl-mode.el (perl-current-defun-name): New.
(perl-mode): Use it.

* lisp/progmodes/scheme.el (scheme-mode-variables, dsssl-mode): Use
lisp-current-defun-name.

* lisp/textmodes/tex-mode.el (tex-current-defun-name): New.
(tex-common-initialization): Use it.

* lisp/textmodes/texinfo.el (texinfo-current-defun-name): New.
(texinfo-mode): Use it.

* lisp/vc/add-log.el (add-log-current-defun-function): Doc fix.
(add-log-current-defun): Move mode-specific code to other files.
(add-log-lisp-like-modes, add-log-c-like-modes)
(add-log-tex-like-modes): Variables deleted.

Fixes: debbugs:2224

2 files changed, 21 insertions, 2 deletions

diff --git a/lisp/textmodes/tex-mode.el b/lisp/textmodes/tex-mode.el
index c4fe0d629b4..966fa60e6de 100644
--- a/lisp/textmodes/tex-mode.el
+++ b/lisp/textmodes/tex-mode.el
@@ -421,6 +421,16 @@ An alternative value is \" . \", if you use a font with a narrow period."
   (if (looking-at latex-outline-regexp)
       (1+ (or (cdr (assoc (match-string 1) latex-section-alist)) -1))
     1000))
+
+(defun tex-current-defun-name ()
+  "Return the name of the TeX section/paragraph/chapter at point, or nil."
+  (when (re-search-backward
+         "\\\\\\(sub\\)*\\(section\\|paragraph\\|chapter\\)"
+         nil t)
+    (goto-char (match-beginning 0))
+    (buffer-substring-no-properties
+     (1+ (point))       ; without initial backslash
+     (line-end-position))))
 
 ;;;;
 ;;;; Font-Lock support
@@ -1202,6 +1212,7 @@ Entering SliTeX mode runs the hook `text-mode-hook', then the hook
   ;; A line starting with $$ starts a paragraph,
   ;; but does not separate paragraphs if it has more stuff on it.
   (setq-local paragraph-separate "[ \t]*$\\|[\f\\\\%]\\|[ \t]*\\$\\$[ \t]*$")
+  (setq-local add-log-current-defun-function #'tex-current-defun-name)
   (setq-local comment-start "%")
   (setq-local comment-add 1)
   (setq-local comment-start-skip
diff --git a/lisp/textmodes/texinfo.el b/lisp/textmodes/texinfo.el
index 91405ba0744..0e45b603c1a 100644
--- a/lisp/textmodes/texinfo.el
+++ b/lisp/textmodes/texinfo.el
@@ -511,6 +511,11 @@ Subexpression 1 is what goes into the corresponding `@end' statement.")
   (regexp-opt (texinfo-filter 2 texinfo-section-list))
   "Regular expression matching just the Texinfo chapter level headings.")
 
+(defun texinfo-current-defun-name ()
+  "Return the name of the Texinfo node at point, or nil."
+  (if (re-search-backward "^@node[ \t]+\\([^,\n]+\\)" nil t)
+      (match-string-no-properties 1)))
+
 ;;; Texinfo mode
 
 ;;;###autoload
@@ -587,8 +592,10 @@ value of `texinfo-mode-hook'."
   (setq-local require-final-newline mode-require-final-newline)
   (setq-local indent-tabs-mode nil)
   (setq-local paragraph-separate
-              (concat "\b\\|@[a-zA-Z]*[ \n]\\|" paragraph-separate))
-  (setq-local paragraph-start (concat "\b\\|@[a-zA-Z]*[ \n]\\|" paragraph-start))
+              (concat "\b\\|@[a-zA-Z]*[ \n]\\|"
+                      paragraph-separate))
+  (setq-local paragraph-start (concat "\b\\|@[a-zA-Z]*[ \n]\\|"
+                                      paragraph-start))
   (setq-local sentence-end-base "\\(@\\(end\\)?dots{}\\|[.?!]\\)[]\"'”)}]*")
   (setq-local fill-column 70)
   (setq-local comment-start "@c ")
@@ -600,6 +607,7 @@ value of `texinfo-mode-hook'."
         '(texinfo-font-lock-keywords nil nil nil backward-paragraph))
   (setq-local syntax-propertize-function texinfo-syntax-propertize-function)
   (setq-local parse-sexp-lookup-properties t)
+  (setq-local add-log-current-defun-function #'texinfo-current-defun-name)
 
   ;; Outline settings.
   (setq-local outline-heading-alist