anchor.diff:  ----
   etc.  More to come.
   
  -===# Keys, keychains, keylinks, and dogtags
  +== [[keys]] Keys, keychains, keylinks, and dogtags
   
   A keylink is a namespaced keyword, e.g. `:Foo/Bar`.  A vector of
   keylinks is a keychain, which corresponds to a datastore Key, which
  
positive.code: (def em2 (entity-map! [:A/B :C/D Foo] m)) ;; long keychains ok too
  ----
  
  ===# field types
  
  The value part of an entity-map is just a map.  The datastore
  restricts the permissible value types; see  link:https://cloud.google.com/appengine/docs/java/datastore/entities#Java_Properties_and_value_types[Properties and value types].
  
negative.code:  (entity-map* :pfx [:A/B :C/D]) ;; fetch all entities with keychain prefix (i.e. ancestor) [:A/B :C/D]
  ----
  
  == [[mutation]] mutation
  
  [[app-listing]]
  [source,clojure]
  