Function select_page 

pub fn select_page<'a>(
    pages: &'a BTreeMap<String, String>,
    pkg_name: &str,
    requested: Option<&str>,
) -> Result<(&'a String, &'a String)>

Picks which manual page to display.

An explicit --page value matches a page file name exactly (e.g. zbsdiff.3). Without it, the <package>.1 page is preferred; a lone page is used directly regardless of its name.

Errors

Returns an error if the requested page does not exist, or if no page can be chosen by default. The error lists the available pages.