Set lisp-data-mode for *.el files under /var and /etc directory

[liuyinz]

Ref: lisp-data-mode

lisp-data-mode is designed for editing non-code Lisp data, which should be fully applied to the data and history file with lisp format in no-littering. Theoretically, packages should set it by themselves, which has been completed in some builtin packages like save-place. However, most famous third-party package like projectile don't recognize this.

I think it would be better to set it by no-littering together. After customization of no-littering, some data files has changed names and paths, for example,

projectile-cache-file is a variable defined in projectile.el.

Value
"/Users/ray/.config/emacs/.cache/var/projectile/cache.el"

Original Value
"/Users/ray/.config/emacs/projectile.cache"

maybe add all *.el files under no-littering-etc-directory and no-littering-var-directory to auto-mode-alist?

(when (fboundp 'lisp-data-mode)
  (add-to-list 'auto-mode-alist
               `(,(concat (regexp-quote no-littering-etc-directory) ".*\\.el\\'")
                 . lisp-data-mode))
  (add-to-list 'auto-mode-alist
               `(,(concat (regexp-quote no-littering-var-directory) ".*\\.el\\'")
                 . lisp-data-mode)))

@tarsius How about this?

[tarsius]

IMO we should only add this to the Suggested Settings section.

[liuyinz]

Agree.