Hello,

I encountered a configuration issue when setting up popper for eshell buffers. When (popper-mode +1) was placed before (setq popper-reference-buffers ... ) in my configuration, e.g. eshell buffers were not being treated as pop-up buffers.

Here is a sample configuration to reproduce the issue:

(require 'popper)
(require 'popper-echo)

(popper-mode +1)
(popper-echo-mode +1)

(setq popper-reference-buffers
      '("\\*Messages\\*"
         "Output\\*$"
         help-mode
         compilation-mode
         "^\\*eshell.*\\*$" eshell-mode ;eshell as a popup
         "^\\*shell.*\\*$"  shell-mode  ;shell as a popup
         "^\\*term.*\\*$"   term-mode   ;term as a popup
         "^\\*vterm.*\\*$"  vterm-mode  ;vterm as a popup
       ))
(setq popper-display-control t)

However, after I placed (popper-mode +1) after popper-reference-buffers, eshell and the other modes started behaving as expected as a pop-up buffer.

It would be helpful if the documentation could mention this configuration order dependency, or if the implementation could be adjusted to avoid this issue.

Thank you for your work on this very useful package.