source-directory is no more

I see that starting with b54, the variable source-directory has been removed. I used to use it to find the origin of the XEmacs source tree, more specifically, the place I could find the TAGS file. I found this generally useful when I was browsing either my own customizations or the XEmacs source. What follows is how I used to do this; I'm sure there's another way to do this - can anyone offer any suggestions? (if (string= (substring source-directory -5) "/lisp") (setq xemacs-source-directory (substring source-directory 0 (- (length source-directory) 5))) (setq xemacs-source-directory source-directory)) (setq tag-table-alist '(("\\.emacs$" . xemacs-source-directory) ("/lisp" . xemacs-source-directory) ((progn (condition-case nil (or (string-match xemacs-source-directory (buffer-file-name)) nil) (error nil))) . xemacs-source-directory))) Thanks in advance, vin