gistfile1.el

(defun git-commit-insert-header (type name email &optional note)
  (let* ((signoff-at (git-commit-find-pseudo-header-position))
         (prev-line  (save-excursion
                       (goto-char (- signoff-at 1))
                       (thing-at-point 'line)))
         (pre        (if (or (string-match "^[^\s:]+:.+$" prev-line)
                             (string-match "\\`\s*$" prev-line))
                         "" "\n"))
         (has-content (stringp note))
         (insert     (lambda ()
                       (goto-char signoff-at)
                       (insert (format "%s%s: %s <%s>\n" pre type name email))
                       (when note
                         (insert (format "[%s: %s]\n" email
                                         (if has-content note "")))
                         (if (not has-text) (backward-char 2)))))
    (if (eq t note)
        (funcall insert)
      (save-excursion
        (funcall insert)))))