*Org Src org-dotemacs.el

(defcustom my-read-only-file-list '()
  "Filenames or patterns that will be opened read-only."
  :group 'my-customizations
  :type '(repeat string)
  )

;; This defun works if called via:
;;   M-: (my-read-only-files)<RET>
;; it sets the buffer read-only iff the file is in my-read-only-file-list
;; but as of Emacs 26, it no longer happens after helm-find-file.
(defun my-read-only-files ()
    "Check if current buffer is in the set of files we want to be
loaded read-only, and if so, make it read-only."
    (dolist (pattern my-read-only-file-list)
      (if (string-match (expand-file-name pattern) buffer-file-name)
          (read-only-mode)
        ))
    )

;; If I describe-variable find-file-hook, I see this in the results
(add-hook 'find-file-hook 'my-read-only-files)