Function blame_file 

pub fn blame_file<S: ObjectSource>(
    source: &S,
    state: &State,
    path: &Path,
    limits: BlameSliceLimits,
) -> Result<FileProvenance, BlameSliceError>

Walk path at state by repeating advance_file_blame_slice until the frontier is exhausted, then finalize. This is not an eager full-file shim; each slice stays inside limits.