[O] Org Agenda - revert all agenda files?

[Xin Shi]

Hello Experts,

In the *Org Agenda* buffer, I usually use the key "r" to refresh the content. If some of the agenda files have change from the disk, it will pop up the question in the mini-buffer to ask what to do. As I choose "r" to revert most of the time, and I have to do several times to revert all the related agenda files. I'm wondering if there is a command to revert all agenda files? Or "force revert"? 

Thanks!

Xin