pub(crate) fn filter_layer(&self) -> eyre::Result<EnvFilter> {
        let mut filter_layer = match EnvFilter::try_from_default_env() {
            Ok(layer) => layer,
            Err(e) => {
                // Catch a parse error and report it, ignore a missing env.
                if let Some(source) = e.source() {
                    match source.downcast_ref::<std::env::VarError>() {
                        Some(std::env::VarError::NotPresent) => (),
                        _ => return Err(e).wrap_err_with(|| "parsing RUST_LOG directives"),
                    }
                }
                EnvFilter::try_new(&format!("{}={}", env!("CARGO_PKG_NAME"), self.log_level()))?
            },
        };
        for directive in &self.log_level {
            // 'clone' the directive. (PR: https://github.com/tokio-rs/tracing/pull/1985)
            let directive_str = directive.to_string();
            let directive = Directive::from_str(&directive_str)?;
            filter_layer = filter_layer.add_directive(directive);
        }

        Ok(filter_layer)
    }

    /// Tracing directives
    ///
    /// This application also understands the `RUST_LOG` environment variable.
    ///
    /// See https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html#directives
    #[clap(long, global = true, group = "verbosity", multiple_occurrences = true)]
    pub(crate) log_level: Vec<Directive>,