Function github_repo_probe 

pub fn github_repo_probe(
    client: &Client,
    url: &str,
    token: Option<&str>,
    policy: &RetryPolicy,
    deadline: Option<Instant>,
    log: &StageLogger,
) -> RepoProbe

Run the GET /repos/{owner}/{repo} request under the shallow probe policy, reading response headers (not just the status) so a secondary-rate-limit 403 is separable from an auth 403. 5xx and retriable transport errors retry within policy and stop once deadline — the invocation’s wall-clock budget — is spent; everything else resolves on the first response.

token is optional: a Some(non-empty) value adds the Authorization bearer header (an empty string is treated as no token — the unauthenticated read path), so the required-token callers pass Some(token) and the best-effort callers can pass None.