これやったら標準の補完がちょっとリッチになった
(add-hook 'minibuffer-setup-hook
(lambda ()
(when (cl-loop with c = (current-local-map)
for m = c then (keymap-parent m)
while m
when (eq m minibuffer-local-completion-map)
return t
finally return nil)
(add-hook 'post-command-hook
(lambda ()
(cl-letf (((symbol-function 'message)
'ignore))
(minibuffer-completion-help)))
nil t))))