testing/graph_in_mem: return values for the rank and parents of NULL_REVISION
… instead of an InvalidKey error, in order to be more consistent with the convention used by the Mercurial implementations.
This instance will be upgraded to Heptapod 18.0.1 on 2025-07-10 between 14:00 and 15:00 UTC+2
… instead of an InvalidKey error, in order to be more consistent with the convention used by the Mercurial implementations.