Function lower_bibliography_directive 

pub(crate) fn lower_bibliography_directive(
    document: &mut Document,
    root: NodeId,
    args: &[SetArg],
    span: &SourceSpan,
    inputs: &mut ExternalInputs<'_>,
    diagnostics: &mut Vec<Diagnostic>,
)

Lower #bibliography("refs.bib") into a bibliography node.

The literal path is recorded under src; the path resolved against the source file’s directory is recorded under resolved_path.