Ask over mesh-sdk's composition: a question makes no pair credential and reads the mesh once (issue 1387)

The callers that only ask (status, the doctor's probes, facts, bindings, data, acts, nodes show, images, release, recorded push, consumers) resolve through resolveNode and compose through composeQuestion, over one Input read per operation (withInputCache). A question composes with Reading or Foreseeing and never calls PairCredential's maker: the credential a send would make is named, and perform makes it on a send.

cmd/mesh-controller/accept_outside.go

@@ -55,6 +55,8 @@ func offeredOutsideBy(ctx context.Context, provision string) (string, error) {
 // its next send would, and the machines that could not be resolved, with why.
 func consumersFrom(ctx context.Context, open *stores, provider, providerModule, provision string) (
 	[]inventory.PairEnd, []string, error) {
+	// One reading of the mesh for every machine this looks at.
+	ctx = withInputCache(ctx)
 	nodes, err := open.inventory.Nodes(ctx)
 	if err != nil {
 		return nil, nil, err
@@ -62,7 +64,7 @@ func consumersFrom(ctx context.Context, open *stores, provider, providerModule,
 	var out []inventory.PairEnd
 	var unresolved []string
 	for _, n := range nodes {
-		plan, _, err := planFor(ctx, open, n.Name)
+		plan, _, err := resolveNode(ctx, open, n.Name)
 		if err != nil {
 			unresolved = append(unresolved, fmt.Sprintf("%s: %s", n.Name, oneLine(err.Error())))
 			continue