Function run_file_diff 

async fn run_file_diff(
    cwd: &Path,
    ref_spec: &str,
    path: &str,
    context: u32,
    budget: Duration,
) -> DiffFetch

Fetch + parse one file’s diff at a given context radius. Binary / submodule entries and empty diffs return Ok(vec![]). Splits the oversize cap from a genuine subprocess crash so the caller can retry oversize at a smaller context instead of failing the whole scan.