-- A build says what it was made from (novox/hq issue 280).
--
-- A rebuild was "no move" only when it made the same artifacts (novox/hq ADR 0236), and an image is not
-- byte-reproducible: a merge that rebuilt the bus without touching its source made a new bus image
-- digest, the mesh read it as a new bus build, and every send to the machine running the bus was
-- refused until a planned bus upgrade. The builder now says what the build was made from — the git
-- tree of the module's directory, the trees of the contexts it read, its bases and toolchains by
-- digest — hashed, and two builds with one source fingerprint are one build.
--
-- Empty for every build recorded before this and for a build whose source does not pin it (one that
-- resolves packages from the registry at build time): those are told apart by their artifacts alone,
-- exactly as before.
alter table build add column source_fingerprint text not null default '';