Tangled to the Homebrew bundle Brewfile:
brew "notmuch" brew "isync" # mbsync
(add-to-list 'load-path "/opt/homebrew/share/emacs/site-lisp/notmuch/") (autoload 'notmuch "notmuch" "notmuch mail" t)
We do not use package.el because we want the Emacs frontend to match
the notmuch binary (that comes with it anyway).