Function href_with_jump_to_def_path_depth 

pub(crate) fn href_with_jump_to_def_path_depth(
    original_did: DefId,
    cx: &Context<'_>,
    jump_to_def_path_depth: Option<usize>,
    preferred_name: Option<&str>,
) -> Result<HrefInfo, HrefError>

If jump_to_def_path_depth is Some, the link comes from a source page and needs that many .. segments to reach the doc root; None generates a link relative to the current page.