Read a new module's directory as its own, not as shared code (hq issue 252)

A merge adding a module the mesh has not registered rebuilt every module
built from the repository. A path under a directory known to hold modules
belongs to that module when its module.json is among the changed files.

cmd/mesh-controller/order_test.go

@@ -147,6 +147,14 @@ func TestAMergeRebuildsTheModulesItChanged(t *testing.T) {
 		{"a module the mesh does not hold", merge([]string{"modules/plex/index.ts"}, false), ""},
 		{"nothing said about the files", merge(nil, false), "gitea,keycloak"},
 		{"more files than were listed", merge([]string{"modules/gitea/index.ts"}, true), "gitea,keycloak"},
+		// novox/hq issue 252: a module the mesh has never registered is still a module, when the merge
+		// shows it is one — and a directory that may be shared code is still shared.
+		{"a new module beside a held one", merge([]string{"modules/gitea/x", "modules/newmod/module.json"}, false), "gitea"},
+		{"a new module's other files", merge([]string{"modules/newmod/index.ts", "modules/newmod/module.json"}, false), ""},
+		{"a module removed", merge([]string{"modules/gone/module.json"}, false), ""},
+		{"a directory with no manifest", merge([]string{"modules/lib/x.go"}, false), "gitea,keycloak"},
+		{"a file directly among the modules", merge([]string{"modules/README.md"}, false), "gitea,keycloak"},
+		{"the root's files still", merge([]string{"tsconfig.json"}, false), "gitea,keycloak"},
 	} {
 		if got := named(whatTheMergeTouched(candidates, known, c.m)); got != c.want {
 			t.Errorf("%s: rebuilt %q, wanted %q", c.what, got, c.want)