(define (job-evaluations->sxml jobs)

(define (register-gc-root drv roots-dir)
  "Register a permanent garbage collector root under ROOTS-DIR for DRV."
  (let ((root (string-append roots-dir "/" (basename drv))))
    (unless (file-exists? root)
      (symlink drv root))))
(define* (job-evaluations->sxml jobs
                                #:key gc-roots-dir)

                (when gc-roots-dir
                  ;; Register DRV as a GC root so that it's not collected by
                  ;; the time 'hydra-build' attempts to build it.
                  (register-gc-root drv gc-roots-dir))

(define (job-evaluations->xml jobs port)

(define* (job-evaluations->xml jobs port
                               #:key gc-roots-dir)

  (sxml->xml (job-evaluations->sxml jobs) port))

  (sxml->xml (job-evaluations->sxml jobs #:gc-roots-dir gc-roots-dir)
             port))

      (job-evaluations->xml jobs (current-output-port)))))

      (unless (string? gc-roots-dir)
        (format (current-error-port)
                "warning: --gc-roots-dir not specified~%"))
      (job-evaluations->xml jobs (current-output-port)
                            #:gc-roots-dir gc-roots-dir))))