Function fetch_updated_at 

pub fn fetch_updated_at(
    bin: &Path,
    refs: &[ItemRef],
) -> Result<Vec<Option<DateTime<Utc>>>>

Fetches only GitHub’s updatedAt for each issue or pull request.

Returns one timestamp per ref in caller order (including duplicates), or None for an item or repository GitHub cannot find. Empty input makes no request. Uses the same repository aliases and bounded batches as fetch_items. Other GraphQL, transport, and malformed timestamp errors fail the call. Blocking — callers must be on a blocking thread.

A caller can retain this timestamp alongside a fetched document, then compare for equality on a later check. Fetch full data with fetch_issues or fetch_items when the timestamp differs (in either direction) or no baseline exists. Neither None nor a failed check certifies a cached copy as fresh. The shallow and full requests are separate, not an atomic snapshot. This helper does not renew IssueCache entries itself.

This checks issue-level edits, including state, labels and new comments. Projects-v2 board/column changes live on ProjectV2Item and do not bump the issue’s updatedAt: this check cannot establish board-state freshness.