4e0a8ae4

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Mutation: one report derivation per instrumented library

mutationCheck now produces one mutation-report derivation per instrumented
library (the combination of its packages and libraries arguments) instead of
a single report covering them all together. The per-library runs build in
parallel and a surviving mutation is attributed to a single library. The
.report passthru is now an attrset keyed by library name (.report.<lib>); the
returned derivation aggregates the per-library pieces under <lib>/.

The mutationCheck API is unchanged; coverage and the diff runner stay
combined.

Timeline