Function scan_without_base_fetch 

pub async fn scan_without_base_fetch<S>(
    cwd: &Path,
    env: &HashMap<String, String, S>,
    prev: Option<&GitDiffSnapshot>,
) -> GitDiffSnapshot
where
    S: BuildHasher,

scan for a read that will fetch the base itself a moment later: the same local scan with none of the background kick, so one read of a sessionless seat pays one fetch - its own - and never queues that fetch behind forge’s on the shared per-repository gate.