Function save_with_options 

pub fn save_with_options(
    obj_store: &GitObjectStore,
    commits_table: Option<&CommitsTable>,
    refs_table: Option<&RefsTable>,
    save_dir: &Path,
    options: &SaveOptions,
) -> Result<SaveMetrics>

Save with options, returning metrics about the operation.

Supports incremental saves (only dirty namespaces) and zstd compression.