Function sync 

pub async fn sync(
    mirror: &Mirror,
    client: Option<&GitHubClient>,
    targets: &Targets,
    force: bool,
) -> SyncReport

Sync everything that is due, and say what moved.

force ignores the schedule — what a refresh button means — but not the ETags: a forced sync of an unchanged repository is still one 304.

client is None when there is no token; the pass then forgets what no project has any more and asks GitHub nothing.