A build records the bases it was handed, and the mesh reads its edges from builds

Bases reach a recipe as build arguments, so the digest was never in the file the builder read
edges from: no build on the mesh recorded what it stood on, and 'build --on', the bases-first
order and the merge follow-up all walked a graph with no edges (novox/hq 04-ISSUES/131). The
builder now reports every base it resolved; the controller records them by artifact path and
reads the newest build's edges from the store, since a recorded manifest carries no build.on.

cmd/mesh-controller/order_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/novox/mesh-controller/internal/catalogue"
@@ -8,19 +9,28 @@ import (
 	"github.com/novox/mesh-controller/internal/link"
 )
 
-func entry(module string, on ...string) inventory.Entry {
-	b := &catalogue.Build{}
-	for _, o := range on {
-		b.On = append(b.On, catalogue.BuildsOn{Arg: "X", Module: o, Artifact: "runtime"})
+// entry is a module as the catalogue holds it: built, so its manifest carries no `build` any more.
+func entry(module string, _ ...string) inventory.Entry {
+	return inventory.Entry{Manifest: catalogue.Manifest{Module: module}}
+}
+
+// stoodOn is what each module's newest build recorded it was handed.
+func stoodOn(edges map[string][]string) map[string][]string {
+	out := map[string][]string{}
+	for module, bases := range edges {
+		for _, b := range bases {
+			out[module] = append(out[module], catalogue.ArtifactStoreScheme+b+"/runtime@sha256:"+strings.Repeat("0", 64))
+		}
 	}
-	return inventory.Entry{Manifest: catalogue.Manifest{Module: module, Build: b}}
+	return out
 }
 
 // A module built before the module it stands on is built against the old one and reports success
 // (novox/hq 04-ISSUES/131). So bases come first, however the set arrived.
 func TestBasesAreBuiltBeforeWhatStandsOnThem(t *testing.T) {
-	in := []inventory.Entry{entry("app", "runtime"), entry("runtime", "base"), entry("other"), entry("base")}
-	got := orderByBases(in)
+	in := []inventory.Entry{entry("app"), entry("runtime"), entry("other"), entry("base")}
+	edges := stoodOn(map[string][]string{"app": {"runtime"}, "runtime": {"base"}})
+	got := orderByBases(in, edges)
 	pos := map[string]int{}
 	for i, e := range got {
 		pos[e.Manifest.Module] = i
@@ -32,12 +42,31 @@ func TestBasesAreBuiltBeforeWhatStandsOnThem(t *testing.T) {
 		t.Fatalf("an entry was lost or doubled: %d", len(got))
 	}
 	// A base outside the set is not waited for: it is not being rebuilt.
-	got = orderByBases([]inventory.Entry{entry("app", "elsewhere")})
+	got = orderByBases([]inventory.Entry{entry("app")}, stoodOn(map[string][]string{"app": {"elsewhere"}}))
 	if len(got) != 1 {
 		t.Fatalf("a dependency outside the set changed the set: %v", got)
 	}
 }
 
+// A module registered from its manifest and never built still names its bases there; once built,
+// the recorded edge is what says so. Both are read, and a module never stands on itself.
+func TestWhatStandsOnAModuleIsReadFromItsBuildOrItsManifest(t *testing.T) {
+	built := entry("gitea")
+	edges := stoodOn(map[string][]string{"gitea": {"mesh-tools"}})
+	if !standsOnModule(built, "mesh-tools", edges) {
+		t.Fatal("a recorded edge was not read")
+	}
+	if standsOnModule(built, "gitea", edges) || standsOnModule(built, "postgres", edges) {
+		t.Fatal("an edge was invented")
+	}
+	fresh := inventory.Entry{Manifest: catalogue.Manifest{Module: "plex", Build: &catalogue.Build{
+		On: []catalogue.BuildsOn{{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"}},
+	}}}
+	if !standsOnModule(fresh, "mesh-tools", nil) {
+		t.Fatal("a manifest's own base was not read")
+	}
+}
+
 // A merge names a repository the way the forge does; a source is recorded the way a build was
 // asked for. The two meet on owner/repo and branch, whichever form the record took.
 func TestAMergeMatchesTheSourcesBuiltFromIt(t *testing.T) {