anchor.diff:  
   (define-command install-os-package ()
     "Install select packages."
  +  (assert-package-manager)
     ;; TODO: Allow profile creation.  Need multi-source support for that?
     (let* ((profile (prompt-minibuffer
                      :suggestion-function (os-profile-suggestion-filter)
  
positive.code: 
  (define-command uninstall-os-package ()
    "Uninstall select packages."
    (let* ((profile (prompt-minibuffer
                     :suggestion-function (os-profile-suggestion-filter)
                     :input-prompt "Target profile"))
  
negative.code:     (set-current-buffer buffer)
      buffer))
  
  (defun assert-package-manager ()
    (unless (ospama:manager)
      (let ((message "No supported package manager detected."))
        (echo message)
        (error message))))
  
  (define-command describe-os-package ()
    "Show description of select packages."
    (assert-package-manager)
    (let* ((packages (prompt-minibuffer
                      :suggestion-function (os-package-suggestion-filter)
                      :input-prompt "Describe OS package(s)"
  