Function blob_text_for_diff 

pub fn blob_text_for_diff(
    git_dir: &Path,
    config: &ConfigSet,
    path: &str,
    blob: &[u8],
    use_textconv: bool,
) -> String

Prepare blob bytes for diff: optional textconv when use_textconv and diff=<driver>.

Does not read or write the textconv notes cache; use blob_text_for_diff_with_oid when the blob OID is known (e.g. commit diffs with cachetextconv).