Add new Renderer type to include full node data without changing node set

The nodes returned from Map2Parent are mostly empty, and need joining with their full topologies
before being useful. But we want to filter out any nodes that weren't already in the graph.

We make a new Renderer type to implement this.
We also add the missing types to the type option group

render/render.go

@@ -55,6 +55,40 @@ func (r *Reduce) Stats(rpt report.Report, dct Decorator) Stats {
 	return result
 }
 
+// ReduceFirstOnly renderer is a Renderer which merges together the output of several other renderers,
+// including only the nodes present in the first render, but merging in info from the same nodes
+// if present in the other renders.
+type ReduceFirstOnly struct {
+	first  Renderer
+	others []Renderer
+}
+
+// MakeReduceFirstOnly is the only sane way to produce a ReduceFirstOnly Renderer.
+func MakeReduceFirstOnly(first Renderer, others ...Renderer) Renderer {
+	r := ReduceFirstOnly{first, others}
+	return Memoise(&r)
+}
+
+// Render produces a set of Nodes given a Report.
+func (r *ReduceFirstOnly) Render(rpt report.Report, dct Decorator) report.Nodes {
+	result := r.first.Render(rpt, dct).Copy()
+	for _, other := range r.others {
+		for id, node := range other.Render(rpt, dct) {
+			if n, ok := result[id]; ok {
+				result[id] = n.Merge(node)
+			}
+		}
+	}
+	return result
+}
+
+// Stats implements Renderer
+func (r *ReduceFirstOnly) Stats(rpt report.Report, dct Decorator) Stats {
+	// Since we're just taking more detailed data from the other renderers,
+	// we probably only care about the filter stats for the 'main' renderer.
+	return r.first.Stats(rpt, dct)
+}
+
 // Map is a Renderer which produces a set of Nodes from the set of
 // Nodes produced by another Renderer.
 type Map struct {