Macro tool_doc

macro_rules! tool_doc {
    (
        $tool: ident,
        $path: literal,
        mode = $mode:expr
        $(, is_library = $is_library:expr )?
        $(, crates = $crates:expr )?
        // Subset of nightly features that are allowed to be used when documenting
        $(, allow_features: $allow_features:expr )?
       ) => { ... };
}