ediff-before-setup-hook is a variable defined in `ediff-init.el'.
Its value is
nil
This variable may be risky if used as a file-local variable.
Documentation:
Hooks to run before Ediff begins to set up windows and buffers.
This hook can be used to save the previous window config, which can be restored
on ediff-quit or ediff-suspend.
You can customize this variable.