anchor.diff:                     (version newest-info))
              (when (or (not prompt)
                        (press-enter-to-continue))
  -             (install-client newest-info local-info)))
  +             (%install-client newest-info local-info)))
             (t
              (format t "The most up-to-date client, version ~A, ~
                         is already installed.~%"
                      (version local-info)))))
     t)
  +
  +
  +(defun install-client (&key url version)
  +  (unless (or url version)
  +    (error "One of ~S or ~S is required" :url :version))
  +  (when (and url version)
  +    (error "Only one of ~S or ~S is allowed" :url :version))
  +  (when version
  +    (setf url (client-info-url-from-version version)))
  +  (let ((local-info (local-client-info))
  +        (new-info (fetch-client-info url)))
  +    (%install-client new-info local-info)))
  
positive.code: ;;;; client-update.lisp
  
  (in-package #:quicklisp-client)
  
  (defun retirement-directory (base)
    (let ((suffix 0))
  
negative.code:                                "client-update"
                                 (version client-info)))))
  
  (defun %install-client (new-info local-info)
    (let* ((work-directory (client-update-scratch-directory new-info))
           (current-quicklisp-directory (qmerge "quicklisp/"))
           (new-quicklisp-directory
            (merge-pathnames "quicklisp/" work-directory))
           (local-temp-tar (merge-pathnames "quicklisp.tar" work-directory))
           (local-setup (merge-pathnames "setup.lisp" work-directory))
           (local-asdf (merge-pathnames "asdf.lisp" work-directory))
           (new-client-tar-p (not (info-equal (client-tar-info new-info)
                                              (client-tar-info local-info))))
           (new-setup-p (not (info-equal (setup-info new-info)
                                         (setup-info local-info))))
           (new-asdf-p (not (info-equal (asdf-info new-info)
                                        (asdf-info local-info)))))
      (ensure-directories-exist work-directory)
      ;; Fetch and unpack quicklisp.tar if needed
      (when new-client-tar-p
        (fetch-client-file-info (client-tar-info new-info) local-temp-tar)
        (unpack-tarball local-temp-tar :directory work-directory))
      ;; Fetch setup.lisp if needed
      (when new-setup-p
        (fetch-client-file-info (setup-info new-info) local-setup))
      ;; Fetch asdf.lisp if needed
      (when new-asdf-p
        (fetch-client-file-info (asdf-info new-info) local-asdf))
      ;; Everything fetched, so move the old stuff away and move the new
      ;; stuff in
      (when new-client-tar-p
        (retire (qmerge "quicklisp/")
                (format nil "quicklisp-~A"
                        (version local-info)))
        (rename-directory new-quicklisp-directory current-quicklisp-directory))
      (when new-setup-p
        (replace-file local-setup (qmerge "setup.lisp")))
      (when new-asdf-p
        (replace-file local-asdf (qmerge "asdf.lisp")))
      ;; But unconditionally move the new client-info into place
      (replace-file (source-file new-info) (qmerge "client-info.sexp"))
      new-info))
  
  (defun update-client (&key (prompt t))
    (let* ((local-info (local-client-info))
  