To attach one file when in message-mode (e.g. when posting from Gnus), one does
C-c C-a. What's the recommended way for attaching multiple files ?
C-c C-a can become tiresome after a while, because it asks three questions everytime.
Attach a file in Emacs is basically just insert a chunk of string containing file paths, you can use yasnippet to create chunks for you.
Here are the steps:
in shell, use find/ls to create the files list to attach
use cli clip tool (putclip on cygwin, pbpaste on Mac, xsel/xclip on linux) to transfer the files list to the yasnippet