Function copy_source_tree_to_artifact 

fn copy_source_tree_to_artifact(
    source: &Path,
    destination: &Path,
    source_root: &Path,
    depth: usize,
    previous_outputs: &BTreeMap<PathBuf, Value>,
    files: &mut u64,
    bytes: &mut u64,
) -> Result<(), i32>

Copies source tree to artifact.