Variable: server-existing-buffer
server-existing-buffer is a buffer-local variable defined in
server.el.gz.
Documentation
Non-nil means the buffer existed before the server was asked to visit it.
This means that the server should not kill the buffer when you say you are done with it in the server.
Source Code
;; Defined in /usr/src/emacs/lisp/server.el.gz
(defvar-local server-existing-buffer nil
"Non-nil means the buffer existed before the server was asked to visit it.
This means that the server should not kill the buffer when you say you
are done with it in the server.")