Popup buffer management with keyboard hints

Just updated Popper for Emacs with hinting in the echo area:

When you toggle a popup, popups for the current context are listed in the echo area along with keyboard hints (M-1 through M-9 by default) to switch to them instantly. The listing is in the order in which the popups are displayed with popper-cycle. Here is a demo of this in action.

There is a dispatch feature included that is currently undocumented. When this transient keymap is active, you can kill any of the popups directly by prefixing the key for that popup with k, i.e. k M-2 to kill the second popup in line. Similarly, ^ M-2 will raise the second popup to being a regular buffer, i.e. persistent and not affected by Popper commands. As usual most of this behaviour is customizable.

The echo area display can be noisy and annoying if you don’t need it, so it’s disabled by default and can be activated as the separate minor mode popper-echo-mode. I added it tentatively, but I find myself using it all the time to switch popup buffers quickly.