Megatest

  ;; special case
  (if (or force (not (hash-table? *configdat*)))  ;; no need to re-open on every call
      (begin
	(set! *configinfo* (or (if (get-environment-variable "MT_CMDINFO") ;; we are inside a test - do not reprocess configs
				   (let ((alistconfig (conc (get-environment-variable "MT_LINKTREE") "/"
							    (get-environment-variable "MT_TARGET")   "/"
							    (get-environment-variable "MT_RUNNAME")  "/"
							    ".megatest.cfg-"  megatest-version "-" megatest-fossil-hash)))
				     (if (file-exists? alistconfig)
					 (list (configf:read-alist alistconfig)
					       (get-environment-variable "MT_RUN_AREA_HOME"))
					 #f))
				   #f) ;; no config cached - give up
			       (let ((runname (or (args:get-arg "-runname")(args:get-arg ":runname"))))
				 (if runname (setenv "MT_RUNNAME" runname))

	    (begin
	      (if (not (file-exists? fulldir))
		  (create-directory fulldir #t)) ;; need to protect with exception handler 
	      (if (and target
		       runname
		       (file-exists? fulldir))
		  (let ((tmpfile  (conc fulldir "/.megatest.cfg." (current-seconds)))
			(targfile (conc fulldir "/.megatest.cfg-"  megatest-version "-" megatest-fossil-hash)))
		    (debug:print-info 0 "Caching megatest.config in " fulldir "/.megatest.cfg")
		    (configf:write-alist *configdat* tmpfile)
		    (system (conc "ln -sf " tmpfile " " targfile))
		    )))))))

(define (get-best-disk confdat)
  (let* ((disks    (hash-table-ref/default confdat "disks" #f))