Add ability to auto-install language grammars

[justinbarclay]

As a follow-up to #7, I've opened up this PR of my work so far for auto-installing grammars based on users' preferences.

To get this to work easily, I expanded treesit-auto to a global minor mode.

This works pretty well for me, as is, but if you want this PR, I am happy to keep tweaking it as you feel necessary 🙂

[renzmann]

Thanks so much for getting this started! I think this will be great functionality to have. Now that we're on MELPA I want to make sure we stick to their guidelines as much as possible. I have three small warnings currently:

⛔ Warning (comp): treesit-auto.el:162:16: Warning: variable `_success' not left unused  
⛔ Warning (comp): treesit-auto.el:161:16: Warning: variable `_grammar-missing' not left unused  
⛔ Warning (comp): treesit-auto.el:183:20: Warning: defcustom for `treesit-auto-minor-mode' fails to specify containing group  

I'll have a chance to look/test more thoroughly this afternoon

[justinbarclay]

Thanks so much for getting this started! I think this will be great functionality to have. Now that we're on MELPA I want to make sure we stick to their guidelines as much as possible. I have three small warnings currently:

⛔ Warning (comp): treesit-auto.el:162:16: Warning: variable `_success' not left unused  
⛔ Warning (comp): treesit-auto.el:161:16: Warning: variable `_grammar-missing' not left unused  
⛔ Warning (comp): treesit-auto.el:183:20: Warning: defcustom for `treesit-auto-minor-mode' fails to specify containing group  

I'll have a chance to look/test more thoroughly this afternoon

Cool, good to know that you're using Melpa standard to lint things. These should be addressed now.

[renzmann]

Here's the config I've used to test it:

  (use-package treesit-auto
    :load-path "~/repos/treesit-auto/"
    :demand t
    :config
    (add-to-list 'treesit-auto-fallback-alist '(bash-ts-mode . sh-mode))
    (advice-add 'treesit-install-language-grammar
		:after (lambda (&rest _r) (treesit-auto-apply-remap)))
    (setq treesit-auto-install 'prompt)
    (global-treesit-auto-mode))

It's working great for me. Thanks for contributing!

[justinbarclay]

Awesome! Thanks for merging this in. 💖

This package is now exactly what I feel the treesit system was missing.