anchor.diff:    (:use :common-lisp :shcl/core/utility :shcl/core/iterator)
     (:import-from :shcl/core/sequence
      #:attachf #:empty-p #:concatenate-sequences #:eager-flatmap-sequence
  -   #:do-while-popf #:eager-map #:eager-filter #:flatten-sequence #:walk)
  +   #:do-while-popf #:eager-map #:eager-filter #:flatten-sequence #:walk #:head
  +   #:tail)
     (:import-from :shcl/core/advice #:define-advice)
     (:import-from :shcl/core/shell-grammar
      #:parse-simple-command #:parse-simple-command-word #:commands-for-tokens)
  
positive.code: (defun all-commands ()
    (concatenate-sequences (all-binary-commands) (all-builtin-commands)))
  
  (defmethod completion-suggestions concatenate-sequences
      ((desired (eql (find-class 'simple-word)))
       (token simple-word)
  
negative.code:   (:import-from :shcl/core/posix-types #:o-rdonly #:st-mode #:x-ok #:at-eaccess)
    (:import-from :shcl/core/support #:s-isdir)
    (:import-from :shcl/core/environment #:colon-list-iterator #:$path)
    (:import-from :shcl/core/expand
     #:compute-expansion-pipeline #:run-expansion-pipeline
     #:wild-path-has-wild-component-p)
    (:import-from :shcl/core/positional-stream
     #:positional-input-stream #:position-record-offset)
    (:import-from :shcl/core/working-directory #:get-fd-current-working-directory)
  