bug#68691: 30.0.50; [WISHLIST] Make it easier to conform to desired commit message format

[Juri Linkov]

> or mark in red any line matching "^lisp/foo/bar.el" (which should be
> a mistake 99.9 % of the time).  Stuff like that.

There is already some linting in log-edit that could be extended further:

  (defconst log-edit-font-lock-gnu-keywords
      ;; Use
      ;;   * foo.el (bla, bli)
      ;;   (blo, blu): Toto.
      ;; Rather than
      ;;   * foo.el (bla, bli,
      ;;   blo, blu): Toto.
    '(("^[ \t]*\\(?:\\* .*\\)?\\(([^\n)]*,\\s-*\\)$"
       (1 '(face font-lock-warning-face
            help-echo "Continue function lists with \")\\n(\".") t))
      ;; Don't leave a lone word on a single line.
      ;;("^\\s-*\\(\\S-*[^\n:)]\\)\\s-*$" (1 font-lock-warning-face t))
      ;; Don't cut a sentence right after the first word (better to move
      ;; the sentence on the next line, then).
      ;;("[.:]\\s-+\\(\\sw+\\)\\s-*$" (1 font-lock-warning-face t))
      ;; Change Log entries should use present tense.
      ("):[ \t\n]*[[:alpha:]]+\\(ed\\)\\>"
       (1 '(face font-lock-warning-face help-echo "Use present tense.") t))
      ;; Change log entries start with a capital letter.
      ("): [a-z]" (0 '(face font-lock-warning-face help-echo "Capitalize.") t))
      ("[^[:upper:]]\\(\\. [[:upper:]]\\)"
       (1 '(face font-lock-warning-face
            help-echo "Use two spaces to end a sentence") t))
      ("^("
       (0 (let ((beg (max (point-min) (- (match-beginning 0) 2))))
            (put-text-property beg (match-end 0) 'font-lock-multiline t)
            (if (eq (char-syntax (char-after beg)) ?w)
                '(face font-lock-warning-face
                  help-echo "Punctuate previous line.")))
          t))
      ))