Handle slash-suffixed web root

src/app.go

@@ -57,6 +57,7 @@ func (a *App) Router() http.Handler {
 	mux.HandleFunc("/status", a.handleStatus)
 	mux.HandleFunc("/pia", a.handlePIA)
 	mux.HandleFunc("/_", a.handleWebRoot)
+	mux.HandleFunc("/_/", a.handleWebRoot)
 	mux.HandleFunc("/_/login", a.handleWebLogin)
 	mux.HandleFunc("/_/chart.js", a.handleWebChartJS)
 	mux.HandleFunc("/_/app.js", a.handleWebAppJS)

src/web_test.go

@@ -64,6 +64,22 @@ func TestWebLoginPageSetsNoStoreHeaders(t *testing.T) {
 	}
 }
 
+func TestWebRootSlashRedirects(t *testing.T) {
+	app := NewApp(Config{APIKey: "super-secret"}, BuildInfo{}, "")
+	req := httptest.NewRequest(http.MethodGet, "/_/", nil)
+	rr := httptest.NewRecorder()
+
+	app.Router().ServeHTTP(rr, req)
+
+	res := rr.Result()
+	if res.StatusCode != http.StatusSeeOther {
+		t.Fatalf("status = %d, want %d", res.StatusCode, http.StatusSeeOther)
+	}
+	if got := res.Header.Get("Location"); got != "/_/login" {
+		t.Fatalf("Location = %q, want /_/login", got)
+	}
+}
+
 func TestWebConfigTogglePersistsToFile(t *testing.T) {
 	dir := t.TempDir()
 	configPath := filepath.Join(dir, "config.json")