journal refuses a boot argument it does not use (issue 1975, AC4); tests cite their acceptance labels

Builds: issue 1975 note 2: lead answer L4, acceptance 1975/AC1-AC4

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

modules/systemd/cmd/systemd-tools/client.go

@@ -319,6 +319,9 @@ func (m *Manager) Journal(scope Scope, unit string, q JournalQuery) (map[string]
 	if err := unitArg(unit); err != nil {
 		return nil, err
 	}
+	if q.Boot != "" {
+		return nil, fmt.Errorf("boot %q: the journal of a unit is not read by boot; kernel-log takes a boot", q.Boot)
+	}
 	q, err := q.valid()
 	if err != nil {
 		return nil, err

modules/systemd/cmd/systemd-tools/journal_test.go

@@ -242,7 +242,7 @@ func TestFailedIsOnTheSeatAndNarrowsToAScope(t *testing.T) {
 	}
 }
 
-// The kernel-log verb (issue 1975): the kernel's messages of one boot, in the journal verb's window, priority,
+// 1975/AC1: kernel-log reads journalctl --dmesg --boot=N under journal's escalation (issue 1975): the kernel's messages of one boot, in the journal verb's window, priority,
 // match, cap and redaction, and a boot named 0, -1, and so on.
 func TestTheKernelLogIsOneBootsMessagesInTheJournalsForms(t *testing.T) {
 	var calls []call
@@ -274,6 +274,7 @@ func TestTheKernelLogIsOneBootsMessagesInTheJournalsForms(t *testing.T) {
 	}
 }
 
+// 1975/AC2: a boot that is not 0 to -9999 is refused and no command runs.
 func TestAKernelLogBootIsRefusedBeforeAnythingRunsUnlessItIsZeroOrBefore(t *testing.T) {
 	for _, bad := range []string{"1", "abc", "--user", "-1 --merge", "-10000", "0x1", "-1;id"} {
 		var calls []call
@@ -287,6 +288,7 @@ func TestAKernelLogBootIsRefusedBeforeAnythingRunsUnlessItIsZeroOrBefore(t *test
 	}
 }
 
+// 1975/AC3: the window, priority, match, 2000-line cap and redaction are journal's.
 func TestTheKernelLogKeepsTheCapTheMatchAndTheRedaction(t *testing.T) {
 	var calls []call
 	m := journalOf([]string{"k one", "k password=hunter2secretvalue here", "k two"}, "", &calls)
@@ -313,3 +315,15 @@ func TestTheKernelLogKeepsTheCapTheMatchAndTheRedaction(t *testing.T) {
 		t.Errorf("a secret in a kernel line was answered: %v", got)
 	}
 }
+
+// 1975/AC4: journal refuses a boot argument it does not use, never reading this boot quietly.
+func TestJournalRefusesABootArgument(t *testing.T) {
+	var calls []call
+	m := journalOf([]string{"a"}, "", &calls)
+	if _, err := m.Journal(System, "mail.service", JournalQuery{Boot: "-1"}); err == nil {
+		t.Fatal("journal accepted a boot and read this boot")
+	}
+	if len(calls) != 0 {
+		t.Fatalf("a refused boot reached the manager: %v", calls)
+	}
+}