//! Requirements rules are additive across layers. Higher-priority rules are//! appended first so the final rule order keeps priority visible.use crate::RequirementSource;use crate::RequirementsExecPolicyToml;use crate::Sourced;use super::stack::merge_output_source;pub(super) fn merge(    target: &mut Option<Sourced<RequirementsExecPolicyToml>>,    incoming: Option<RequirementsExecPolicyToml>,    source: &RequirementSource,) {    let Some(incoming) = incoming else {        return;    };    let Some(existing) = target.as_mut() else {        *target = Some(Sourced::new(incoming, source.clone()));        return;    };    let RequirementsExecPolicyToml { prefix_rules } = incoming;    existing.value.prefix_rules.extend(prefix_rules);    merge_output_source(&mut existing.source, source);}