https://stackoverflow.com/questions/384284/how-do-i-rename-an-open-file-in-emacs

;; source: http://steve.yegge.googlepages.com/my-dot-emacs-file

(defun rename-file-and-buffer (new-name)

“Renames both current buffer and file it’s visiting to NEW-NAME.”

(interactive “sNew name: “)

(let ((name (buffer-name))

(filename (buffer-file-name)))

(if (not filename)

(message “Buffer ‘%s’ is not visiting a file!” name)

(if (get-buffer new-name)

(message “A buffer named ‘%s’ already exists!” new-name)

(progn

(rename-file filename new-name 1)

(rename-buffer new-name)

(set-visited-file-name new-name)

(set-buffer-modified-p nil))))))