A no-op build's ~2-3s was almost all registry I/O:
- the base index was fetched 3x (BasePlatforms + remote.Image per platform)
- the base's top layer was downloaded once per platform every build to read
/etc/apko.json for interpreter detection (Chainguard has no PYTHON_VERSION)
Changes:
- build.BaseSet resolves the base reference once and serves per-platform child
images memoized (index fetched once; verified by TestBaseSet)
- cache the detected interpreter version by base digest in a default per-user
metadata cache (cache.GetText/PutText), so repeat builds skip the apko layer
download
- lazy wheel-cache dir creation; wheelhouse.Resolve defaults to the per-user
cache dir
Tests: TestBaseSet (index fetched once + per-platform memoized), TestCachedInterpreter
(write + cache-hit short-circuit), cache text round-trip.
Co-authored-by: Jason Hall <imjasonh@users.noreply.github.com>
