A revision that changes only the user list is written into the bus node's want at once, outside the record hold
(ADR 0539 clause 7), so the assigner must tell it apart from a move that recreates or moves data.
The controller writes one module's composition per node and fingerprint, and the assigner reads its digest and
judgement before it writes a want (ADR 0539 clauses 1, 2 and 14).
jschoubben