A store with a history of every kind of change an entry can make, for the web UI's tests: edits, a definition re-hashed only because what it uses changed, a rename, an alias, a type changing beside a value of the same name, a conflict, a removal and an addition. Its entries, oldest first.
What the history says each entry changed is what diffNamespaces says, of the entry's names and its parent's read whole, whichever order the entries are asked for in (each entry's names are made from the last ones read).