Build every judge where no pull request can reach, and never read mesh-lab at a release

Review of #329: a judge built with HOME in the workspace runs git under a
configuration a pull request's script can plant, so a hook could rewrite the
judge's sources before they compile and the result be kept under an honest key
(issue 482, issue 704). Every judge now builds with its own HOME, configuration
and Go cache outside the workspace, no git configuration and no VCS stamping.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/builder/release_branch_test.go

@@ -144,6 +144,7 @@ run)
   if [ -n "$detached" ]; then echo a-container; exit 0; fi
   shift
   if [ "$1" = go ]; then echo "GOCACHE=$GOCACHE GOENV=$GOENV $*" >> "` + built + `"; fi
+  if [ "$1" = go ] && [ "$2" = build ] && [ -n "$JUDGE_HOMES" ]; then echo "$HOME" >> "$JUDGE_HOMES"; fi
   cd "$workdir" && exec "$@" ;;
 esac
 exit 1
@@ -258,8 +259,8 @@ func TestACataloguePullRequestIntoAReleaseBranchIsJudgedByThatBranchsController(
 	// **The judge is built with a cache no pull request's script can write** (issue 482): a fresh one under the
 	// check's own root, never the workspace's shared go-cache, and no Go environment file from the workspace's HOME.
 	said, _ := os.ReadFile(built)
-	if !strings.Contains(string(said), "/check/judge-go-cache GOENV=off go build") ||
-		strings.Contains(string(said), "/go-cache GOENV") {
+	if !strings.Contains(string(said), "/mesh-check-judge-") || !strings.Contains(string(said), "GOENV=off go build") ||
+		strings.Contains(string(said), "/check/../go-cache") {
 		t.Fatalf("the release judge was built with the workspace's cache or Go environment:\n%s", said)
 	}
 
@@ -412,3 +413,135 @@ func TestAReleaseBranchCheckReadsMeshLabAtItsTrunkEvenWhenItHasThatBranch(t *tes
 			labMain[:12])
 	}
 }
+
+// aPlantedWorkspace is a workspace a pull request's own script has written into, as it can: a git configuration in its
+// HOME whose fsmonitor hook says each directory git runs in, a git configuration under XDG_CONFIG_HOME doing the same,
+// and a Go environment file that would hand the judge's build a tool of its own. It answers the workspace and the
+// file the hook writes to.
+func aPlantedWorkspace(t *testing.T) (string, string) {
+	t.Helper()
+	workspace, logs := t.TempDir(), t.TempDir()
+	ran := filepath.Join(logs, "hook-ran")
+	hook := filepath.Join(workspace, "hook.sh")
+	files := map[string]string{
+		hook:                                   "#!/bin/sh\necho \"$PWD\" >> " + ran + "\n",
+		filepath.Join(workspace, ".gitconfig"): "[core]\n\tfsmonitor = " + hook + "\n",
+		filepath.Join(workspace, ".config", "git", "config"): "[core]\n\tfsmonitor = " + hook + "\n",
+		filepath.Join(workspace, ".config", "go", "env"):     "GOFLAGS=-toolexec=" + hook + "\n",
+	}
+	for name, body := range files {
+		if err := os.MkdirAll(filepath.Dir(name), 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(name, []byte(body), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	return workspace, ran
+}
+
+// judgeRanTheHook says whether the planted hook ran in a judge's tree: the controller beside the check, or the
+// change's own when it judges itself.
+func judgeRanTheHook(t *testing.T, ran string) string {
+	t.Helper()
+	body, _ := os.ReadFile(ran)
+	for _, line := range strings.Split(string(body), "\n") {
+		if strings.HasSuffix(line, "/check/mesh-controller") {
+			return string(body)
+		}
+	}
+	return ""
+}
+
+// **Every judge is built where no pull request reaches** (issue 482, ADR 0358 review): a git configuration with a
+// hook, and a Go environment file, planted in the workspace by an earlier pull request's script, do not run during
+// the release judge's build — while the pull request's own script, in the workspace, still meets them.
+func TestAHookPlantedInTheWorkspaceDoesNotRunDuringTheReleaseJudgesBuild(t *testing.T) {
+	aRuntimeThatBuildsTheJudge(t)
+	homes := filepath.Join(t.TempDir(), "homes")
+	t.Setenv("JUDGE_HOMES", homes)
+	registry := aFactsRegistry(t)
+	workspace, ran := aPlantedWorkspace(t)
+	beside, _, _, _ := theReleasedMesh(t)
+	catalogue, head := aPullRequestInto(t, map[string]string{"modules/gitea/module.json": `{"module":"gitea"}`,
+		CheckScript: "git status >/dev/null 2>&1; true\n"}, releaseBranch, map[string]string{"modules/gitea/index.ts": "x"})
+	v, err := Check(t.Context(), Command, CheckSpec{ID: "check-704-planted", Repository: catalogue, Ref: head,
+		Owner: "novox", Repo: "mesh-catalog", Number: 286, Base: releaseBranch, Release: releaseBranch,
+		JudgeCache: t.TempDir(), Paths: []string{"modules/gitea/index.ts"}, Modules: []string{"gitea"}, Beside: beside,
+		Toolchain: "golang"}, workspace, registry, GitCredential{}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if v.Gate == nil || v.Gate.Verdict != "pass" {
+		t.Fatalf("the check did not judge: %+v\n%s", v.Gate, v.Report)
+	}
+	if body, _ := os.ReadFile(ran); !strings.Contains(string(body), "/check/mesh-catalog") {
+		t.Fatalf("the planted hook never ran, so this test proves nothing: %q", body)
+	}
+	if said := judgeRanTheHook(t, ran); said != "" {
+		t.Fatalf("the hook planted in the workspace ran during the judge's build:\n%s", said)
+	}
+	if body, _ := os.ReadFile(homes); len(body) == 0 || strings.Contains(string(body), workspace) {
+		t.Fatalf("the judge was built with a HOME in the workspace: %q", body)
+	}
+}
+
+// The same for the judge built with a node-engine change's own validator, into a release branch (ADR 0358 §2).
+func TestAHookPlantedInTheWorkspaceDoesNotRunDuringTheValidatorJudgesBuild(t *testing.T) {
+	aRuntimeThatBuildsTheJudge(t)
+	homes := filepath.Join(t.TempDir(), "homes")
+	t.Setenv("JUDGE_HOMES", homes)
+	registry := aFactsRegistry(t)
+	workspace, ran := aPlantedWorkspace(t)
+	beside, _, _, _ := theReleasedMesh(t)
+	delete(beside, "mesh-host")
+	files := aHostSaying("the release branch's validator")
+	files["module.json"] = `{"module":"mesh-host"}`
+	files[CheckScript] = "git status >/dev/null 2>&1; true\n"
+	host, head := aPullRequestInto(t, files, releaseBranch, aHostSaying("this change's validator"))
+	v, err := Check(t.Context(), Command, CheckSpec{ID: "check-704-planted-validator", Repository: host, Ref: head,
+		Owner: "novox", Repo: "mesh-host", Number: 111, Base: releaseBranch, Release: releaseBranch, Judge: "validator",
+		JudgeCache: t.TempDir(), Paths: []string{"validate/v.go"}, Modules: []string{"mesh-host"}, Beside: beside,
+		Toolchain: "golang"}, workspace, registry, GitCredential{}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if v.Gate == nil || !strings.HasSuffix(v.Gate.Summary, "the release branch's controller with this change's validator") {
+		t.Fatalf("a node-engine change into a release branch was not judged by that branch's controller with its own "+
+			"validator: %+v\n%s", v.Gate, v.Report)
+	}
+	if body, _ := os.ReadFile(ran); !strings.Contains(string(body), "/check/mesh-host") {
+		t.Fatalf("the planted hook never ran, so this test proves nothing: %q", body)
+	}
+	if said := judgeRanTheHook(t, ran); said != "" {
+		t.Fatalf("the hook planted in the workspace ran during a judge's build:\n%s", said)
+	}
+	if body, _ := os.ReadFile(homes); strings.Count(string(body), "\n") != 2 || strings.Contains(string(body), workspace) {
+		t.Fatalf("the judges were not both built with a HOME outside the workspace: %q", body)
+	}
+}
+
+// **mesh-lab is never read at a release branch**, asked with a fallback or without (ADR 0358).
+func TestTheBuildSeatNeverReadsMeshLabAtAReleaseBranch(t *testing.T) {
+	aRuntimeThatBuildsTheJudge(t)
+	registry := aFactsRegistry(t)
+	lab, labMain, _ := aRepositoryWithARelease(t, map[string]string{"README": "the lab"},
+		map[string]string{"README": "a branch anyone could push"})
+	for _, asked := range []Beside{{Repository: lab, Ref: releaseBranch}, {Repository: lab, Ref: releaseBranch, Else: "main"}} {
+		beside, _, _, _ := theReleasedMesh(t)
+		beside["mesh-lab"] = asked
+		catalogue, head := aPullRequestInto(t, map[string]string{"modules/gitea/module.json": `{"module":"gitea"}`,
+			CheckScript: "true\n"}, releaseBranch, map[string]string{"modules/gitea/index.ts": "x"})
+		v, err := Check(t.Context(), Command, CheckSpec{ID: "check-704-lab-asked", Repository: catalogue, Ref: head,
+			Owner: "novox", Repo: "mesh-catalog", Number: 286, Base: releaseBranch, Release: releaseBranch,
+			JudgeCache: t.TempDir(), Paths: []string{"modules/gitea/index.ts"}, Modules: []string{"gitea"}, Beside: beside,
+			Toolchain: "golang"}, t.TempDir(), registry, GitCredential{}, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if v.BesideAt["mesh-lab"] != "main" || v.Beside["mesh-lab"] != labMain[:12] {
+			t.Fatalf("mesh-lab asked as %+v was read at %q (%s), not main at %s", asked, v.BesideAt["mesh-lab"],
+				v.Beside["mesh-lab"], labMain[:12])
+		}
+	}
+}