anchor.diff:  			 (namestring (merge-pathnames "xargs-data.sexp"))
   			 depth)))))
   	
  -	(let ((if-exists (if (eql if-exists :supersede) nil if-exists)))
  +	(let ((if-exists (case if-exists
  +			   (:supersede-all
  +			    :supersede)
  +			   (:supersede
  +			    nil)
  +			   (t
  +			    (if if-exists-p
  +				if-exists
  +				:error)))))
   	  (with-open-file (out "xargs-arguments" :if-exists if-exists :direction :output)
   	    (when out
   	      (write-string *xargs-arguments-string* out)))
  
positive.code: 	(error "Directory ~S already exists!" directory))
  
        (let ((*default-pathname-defaults* (parse-namestring pathspec)))
  	(let ((if-exists (if (eql if-exists :supersede-all) :supersede if-exists)))
  	  (write-program-data "xargs-data.sexp" area tree :if-exists if-exists)
  
  	  (with-open-file (out "xargs-program.sh" :if-exists if-exists :direction :output)
  
negative.code:   #- (or darwin linux)
    (error "XARGS-SEQUENCE is not supported on your operating system."))
  
  (defun prepare-xargs-script (directory area tree program &key (if-exists :error if-exists-p))
    (declare (type (member :error :supersede :supersede-all) if-exists))
    (let ((program-path (if (listp program)
  			  (apply #'lisp-executable-pathname program)
  