Extends the builtin default policy to verify docker-github-builder
signatures on docker/buildkit-syft-scanner images. Tags `latest` and
1.10+ require a signature from the docker/buildkit-syft-scanner source
repository; older tags pass through unchanged. Factors the shared ref
matching logic into sig_ref_matches for dockerfile and introduces a
syft-scanner variant that uses the plain refs/tags/ prefix.
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
Tonis Tiigi
0491d7c7b9