anchor.diff:    The path is called the locative. A locative can be applied to an
     object like this:
   
  -      (locate 'foo 'variable)
  +  ```
  +  (locate 'foo 'variable)
  +  ```
   
     which will return the same reference as `(MAKE-REFERENCE 'FOO
     'VARIABLE)`. Operations need to know how to deal with references
  
positive.code:   "One may wish to make the DOCUMENT function and `M-.` navigation
    work with new object types. Extending DOCUMENT can be done by
    defining a DOCUMENT-OBJECT method. To allow these objects to be
    referenced from DEFSECTION a LOCATE-OBJECT method is to be defined.
    Finally, for `M-.` FIND-SOURCE can be specialized. Finally,
    EXPORTABLE-LOCATIVE-TYPE-P may be overridden if exporting does not
    makes sense. Here is a stripped down example of how all this is done
  
negative.code:   no first class object to represent the thing of interest. Recall
    that LOCATE returns a REFERENCE object in this case. DOCUMENT-OBJECT
    and FIND-SOURCE defer to LOCATE-AND-DOCUMENT and
    LOCATE-AND-FIND-SOURCE, which have LOCATIVE-TYPE in their argument
    list for EQL specializing pleasure. Here is a stripped down example
    of how the VARIABLE locative is defined:"
    (variable-example (include (:start (variable locative)
  