Function pr_cache_fresh 

fn pr_cache_fresh(
    prev: Option<&GitDiffSnapshot>,
    branch: &str,
    pushed_sha: Option<&str>,
    now: SystemTime,
) -> bool

Whether the previous snapshot’s PR block is still reusable: the branch name and pushed sha both match the current scan AND the last lookup attempt is less than PR_REFETCH_INTERVAL old. The sha leg - not the branch name - is what makes a PR opened or pushed after an earlier scan show up; the timer leg unsticks a cached None (a scan that ran before the PR existed would otherwise hold pr: None for the branch’s whole life).