Fix About-page version check broken by OCI image index (0.22.4)

[PeterRounce]

Problem

The About page shows Latest Version: "unable to check" and the "Update available" button never appears on any deployed hub — logged as WARN CheckLatestVersion: no config digest in manifest.

CheckLatestVersion read manifest.Config.Digest, assuming a single-platform Docker v2 manifest with a top-level config. Since CI switched to docker/build-push-action@v6 (#43, v0.22.2), buildx pushes boltcard/card:latest as an OCI image index (application/vnd.oci.image.index.v1+json) with provenance attestations on by default — a manifests[] array and no top-level config. So the digest came back empty and the check bailed out, even though the version label is present one level deeper. See #45 for the full investigation with registry evidence.

Two complementary fixes

1. Go: parse the index (forward fix — new hubs)

• parseManifest — a plain image manifest yields the config digest; an image index / manifest list yields the linux/amd64 child manifest digest (skips the attestation-manifest entry, falls back to any non-attestation platform for arm64-only builds).
• resolveConfigDigest — follows one index indirection (index → image manifest → config).
• fetchManifest — Accept header now advertises the OCI index / Docker manifest-list types alongside the single-image types.

2. CI: publish a single-platform manifest (rescues existing installs)

The Go fix only helps hubs already running the new code. Already-deployed hubs (<=0.22.3) still run the broken parser, so they'd never see the button offering the update that fixes them — a chicken-and-egg lockout.

The only lever over an already-running hub is what we publish to Docker Hub. Setting provenance: false on the build-push-action steps makes buildx publish a plain single-platform manifest instead of a provenance index. Verified against the live registry: Docker Hub serves a single-platform manifest (even an OCI one) to the old code's narrow Accept header with a top-level config.digest — so the old parser succeeds and the button reappears. After the first release built this way, every stuck hub can finally see and click Update.

Verification

• New unit tests (update_test.go) cover the OCI index, plain-manifest, fallback, and error paths.
• End-to-end against the live Docker Hub registry: CheckLatestVersion() now returns 0.22.3 (was "").
• Registry content-negotiation probe confirms the old narrow Accept header still gets a parseable single manifest.
• go vet, go build, and go test -race ./... all pass; ci.yml validated.

Fixes #45

🤖 Generated with Claude Code