Trust a module's trunk for who can merge into it, not for a required status (ADR 0534 §6)

The forge requires no status to merge any more (ADR 0534 §1); a trunk is
trusted when it takes no push, its merge whitelist names mesh-tools alone and
no administrator merges past its rule, so only mesh-delivery lands a commit
there, on a passing mesh/check and the operator's Approve. The old rule failed
the 11:51 delivery plan once mesh-catalog's status was unticked.

cmd/mesh-controller/build_source.go

@@ -205,8 +205,9 @@ func (f *sourceForms) buildsFrom(entries []inventory.Entry, repository, seat str
 type forgeFacts struct {
 	// ID is the forge's own id of the repository: what tells it from one deleted and made again by its name.
 	ID int64
-	// Guarded is whether the branch is protected as a module's trunk must be: no direct push, at least one
-	// required status, and no administrator merging past one. Why says what is missing when it is not.
+	// Guarded is whether the branch is protected as a module's trunk must be: no direct push, a merge whitelist naming
+	// the tools' account alone, and no administrator merging past the rule (novox/hq ADR 0534 §6; no required status,
+	// which the forge no longer asks, §1). Why says what is missing when it is not.
 	Guarded bool
 	Why     string
 }
@@ -361,27 +362,39 @@ func askTheForgeOnce(ctx context.Context, owner, repo, branch string) (forgeFact
 	return facts, nil
 }
 
+// forgeToolsAccount is the forge tools' account, the only one main's merge whitelist names (novox/hq ADR 0398 §2, the
+// gitea module's tools-account.ts TOOLS_ACCOUNT): only mesh-delivery, through the merge tool, lands a commit on a trunk.
+const forgeToolsAccount = "mesh-tools"
+
 // protectionRule is a branch protection rule as the forge's tool summarises it.
 type protectionRule struct {
 	Rule             string   `json:"rule"`
 	Push             bool     `json:"push"`
 	RequiredStatuses []string `json:"required_statuses"`
 	AdminMayOverride bool     `json:"admin_may_override"`
+	// MergeWhitelist is who may merge into the branch; nil when the rule keeps no merge whitelist (anyone who writes).
+	MergeWhitelist []string `json:"merge_whitelist"`
 }
 
 // judgedRule judges the one rule the forge applies to a branch, as the forge picks it: the rule named for the
 // branch, else the first glob rule, in the forge's order, that covers it (gitea's first matching rule). Never a
-// later rule that happens to be stronger: the forge does not read it.
+// later rule that happens to be stronger: the forge does not read it. A trunk is trusted for who can land a commit on
+// it, not for a status it requires (novox/hq ADR 0534 §6): no push, only the tools' account merges, and no administrator
+// merging past the rule; then only mesh-delivery lands a commit there, through the merge tool, on a passing mesh/check
+// and the operator's Approve (ADR 0534 §4).
 func judgedRule(rules []protectionRule, branch string) forgeFacts {
 	switch r := appliedRule(rules, branch); {
 	case r == nil:
 		return forgeFacts{Why: fmt.Sprintf("no protection rule covers %s", branch)}
 	case r.Push:
 		return forgeFacts{Why: fmt.Sprintf("the rule %s lets a person push to %s directly", r.Rule, branch)}
-	case len(r.RequiredStatuses) == 0:
-		return forgeFacts{Why: fmt.Sprintf("the rule %s requires no status before a merge into %s", r.Rule, branch)}
+	case r.MergeWhitelist == nil || len(r.MergeWhitelist) == 0:
+		return forgeFacts{Why: fmt.Sprintf("the rule %s keeps no merge whitelist naming %s alone for %s", r.Rule, forgeToolsAccount, branch)}
+	case len(r.MergeWhitelist) != 1 || r.MergeWhitelist[0] != forgeToolsAccount:
+		return forgeFacts{Why: fmt.Sprintf("the rule %s lets %s merge into %s, not %s alone", r.Rule,
+			strings.Join(r.MergeWhitelist, ", "), branch, forgeToolsAccount)}
 	case r.AdminMayOverride:
-		return forgeFacts{Why: fmt.Sprintf("the rule %s lets an administrator merge into %s past a status", r.Rule, branch)}
+		return forgeFacts{Why: fmt.Sprintf("the rule %s lets an administrator merge into %s past it", r.Rule, branch)}
 	}
 	return forgeFacts{Guarded: true}
 }

cmd/mesh-controller/build_source_test.go

@@ -102,16 +102,17 @@ func init() {
 // The forge applies one rule to a branch: the rule named for it, else the first glob that covers it. A stronger
 // rule later in the list is not what guards the branch, and is not read as if it were (the confirmation review).
 func TestTheRuleJudgedIsTheOneTheForgeApplies(t *testing.T) {
-	guarded := protectionRule{Rule: "*", RequiredStatuses: []string{"mesh/merge-gate"}}
-	open := protectionRule{Rule: "main", Push: true, RequiredStatuses: []string{"mesh/merge-gate"}}
+	tools := []string{forgeToolsAccount}
+	guarded := protectionRule{Rule: "*", MergeWhitelist: tools}
+	open := protectionRule{Rule: "main", Push: true, MergeWhitelist: tools}
 	if f := judgedRule([]protectionRule{guarded, open}, "main"); f.Guarded {
 		t.Error("an exact rule letting pushes was passed over for a glob that guards")
 	}
-	if f := judgedRule([]protectionRule{{Rule: "ma*", RequiredStatuses: nil}, {Rule: "*", RequiredStatuses: []string{"x"}}},
+	if f := judgedRule([]protectionRule{{Rule: "ma*", MergeWhitelist: nil}, {Rule: "*", MergeWhitelist: tools}},
 		"main"); f.Guarded || !strings.Contains(f.Why, "ma*") {
 		t.Errorf("the first glob covering the branch was not the one judged: %+v", f)
 	}
-	if f := judgedRule([]protectionRule{{Rule: "release/*"}, {Rule: "main", RequiredStatuses: []string{"x"}}}, "main"); !f.Guarded {
+	if f := judgedRule([]protectionRule{{Rule: "release/*"}, {Rule: "main", MergeWhitelist: tools}}, "main"); !f.Guarded {
 		t.Errorf("the rule named for the branch was not judged: %+v", f)
 	}
 	if f := judgedRule(nil, "main"); f.Guarded {
@@ -119,6 +120,36 @@ func TestTheRuleJudgedIsTheOneTheForgeApplies(t *testing.T) {
 	}
 }
 
+// **A module's trunk is trusted when it takes no push, only the tools' account merges into it, and no administrator
+// merges past its rule** (novox/hq ADR 0534 §6): the forge requires no status to merge (§1), so a rule requiring none is
+// trusted; one with no merge whitelist, another name in it, a push allowed or an administrator's override is not.
+func TestATrunkIsTrustedForItsMergersNotForAStatus(t *testing.T) {
+	tools := []string{forgeToolsAccount}
+	for _, c := range []struct {
+		name string
+		rule protectionRule
+		want bool
+		why  string
+	}{
+		{"no status, no push, the tools alone merge", protectionRule{Rule: "main", MergeWhitelist: tools}, true, ""},
+		{"a status required as well", protectionRule{Rule: "main", MergeWhitelist: tools, RequiredStatuses: []string{"mesh/check"}}, true, ""},
+		{"no merge whitelist", protectionRule{Rule: "main"}, false, "merge whitelist"},
+		{"an empty merge whitelist", protectionRule{Rule: "main", MergeWhitelist: []string{}}, false, "merge whitelist"},
+		{"another name in the whitelist", protectionRule{Rule: "main", MergeWhitelist: []string{forgeToolsAccount, "agent-ace"}}, false, "agent-ace"},
+		{"another name alone", protectionRule{Rule: "main", MergeWhitelist: []string{"agent-ace"}}, false, "agent-ace"},
+		{"a push allowed", protectionRule{Rule: "main", Push: true, MergeWhitelist: tools}, false, "push"},
+		{"an administrator's override", protectionRule{Rule: "main", MergeWhitelist: tools, AdminMayOverride: true}, false, "administrator"},
+	} {
+		f := judgedRule([]protectionRule{c.rule}, "main")
+		if f.Guarded != c.want || !strings.Contains(f.Why, c.why) {
+			t.Errorf("%s: %+v, want guarded %v saying %q", c.name, f, c.want, c.why)
+		}
+		if strings.Contains(f.Why, "requires no status") {
+			t.Errorf("%s: a trunk is still judged on a required status: %s", c.name, f.Why)
+		}
+	}
+}
+
 // An id the forge could not give keeps the id already recorded.
 
 // **The operator's Approve of a reviewed group registers a moved module from its new repository** (novox/hq ADR 0420 §7,