Function datman::commands::backup::backup_source_to_destination

pub fn backup_source_to_destination(
    source: &SourceDescriptor, 
    dest: &DestPileDescriptor, 
    descriptor: &Descriptor, 
    desc_path: &Path, 
    source_name: &str, 
    dest_name: &str, 
    num_workers: u8
) -> Result<()>