display-buffer-base-action is a variable defined in `window.el'.
Its value is

  • This variable may be risky if used as a file-local variable.

User-specified default action for `display-buffer'.
It should be a cons cell (FUNCTION . ALIST), where FUNCTION is a
function or a list of functions. Each function should accept two
arguments: a buffer to display and an alist similar to ALIST.
See `display-buffer' for details.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.