ADR 0447 §1 has main require mesh/check alone. The repositories program now
requires it in place of mesh/merge-gate and mesh/repo-check on every listed
repository and on every other one whose main requires mesh/merge-gate, so the
switch needs no hand-kept list (lead decisions L4, L11). A main requiring
mesh/repo-check alone (hq) keeps it until issue 1296 (ADR 0503 §5).