I look around a bit and didn't find an answer that fit with my current situation. I have a app.js file:
'use strict';
var demoApp = angular.module('demoApp', [
    // Dépendances du "module" <-- demoApp
    'ngRoute',
    'routeAppControllers',
    'todoList'
]);
demoApp.config(['$routeProvider', '$locationProvider',
    function($routeProvider, $locationProvider) { 
        // Système de routage
        $routeProvider
        .when('/home', {
            templateUrl: 'views/home.html',
            controller: 'homeCtrl'
        })
        .when('/contact/:msg?', {
            templateUrl: 'views/contact.html',
            controller: 'contactCtrl'
        })
        .when('/todolist', {
            templateUrl: 'views/todolist.html',
            controller: 'listeCtrl'
        })
        .when('/testfiltre', {
            templateUrl: 'views/testfiltre.html',
            controller: 'demoFiltreCtrl'
        })
        .when('/testCreationfiltre', {
            templateUrl: 'views/testcreationfiltre.html',
            controller: 'demoCreationFiltreCtrl'
        })
        .otherwise({
            redirectTo: '/home'
        });
    }
]);
var routeAppControllers = angular.module('routeAppControllers', []);
routeAppControllers.controller('homeCtrl', ['$scope',
    function($scope){
        $scope.message = "Bienvenue sur la page d'accueil";
    }
]);
routeAppControllers.controller('contactCtrl', ['$scope','$routeParams',
    function($scope, $routeParams){
        $scope.message = "Laissez-nous un message sur la page de contact !";
        $scope.msg = $routeParams.msg || "Bonne chance pour cette nouvelle appli !";
    }
]);
routeAppControllers.controller('listeCtrl', [function(){}]);
I have todolist module in todolist_controller.js:
var todoList=angular.module('todoList',[]);
todoList.controller('todoCtrl', ['$scope',
    function ($scope) {
        var todos = $scope.todos = [];
        $scope.addTodo = function () {
            var newTodo = $scope.newTodo.trim();
            if (!newTodo.length) {
                return;
            }
            todos.push({
                title: newTodo,
                completed: false
            });
            $scope.newTodo = '';
        };
        $scope.removeTodo = function (todo) {
            todos.splice(todos.indexOf(todo), 1);
        };
        $scope.markAll = function (completed) {
            todos.forEach(function (todo) {
                todo.completed = completed;
            });
        };
        $scope.clearCompletedTodos = function () {
            $scope.todos = todos = todos.filter(function (todo) {
                return !todo.completed;
            });
        };
    }
]);
I have my index.html page:
<!DOCTYPE html>
    <html lang="fr" ng-app="demoApp">
        <head>
            <meta charset="utf-8" />
            <title>Demo App</title>        
            <link rel="stylesheet" href="styles/style.css">
            <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.2/angular.js"></script>
            <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.2/angular-route.js"></script>
            <script src="https://cdnjs.cloudflare.com/ajax/libs/angular-i18n/1.4.2/angular-locale_fr-ca.min.js"></script>
            <script src="scripts/controllers/app.js"></script>
            <script src="scripts/controllers/todolist_controllers.js"></script>
        </head>
        <body>
            <div ng-view>
            </div>
            <nav>
                <a href="#/home" class="btn btn-primary">Page d'accueil</a>
                <a href="#/contact" class="btn btn-success">Page de contact</a>
                <a href="#/todolist" class="btn btn-primary">Todo list</a>
                <a href="#/testfiltre" class="btn btn-success">test filtre</a>
                <a href="#/testCreationfiltre" class="btn btn-primary">test création filtre</a>
            </nav>
        </body>
    </html>
I read that I'm suppose to call, for example, my main module App and all my other module file should start with: angular.module('App').controller(...
But, this would imply that if I change the name of my app from 'app' to 'my_app' for example, I would have to go trough all my controllers and change 'app' for 'my-app'.
I would like to avoid that and just be able to import my file in index.html and just have to declare it in the dependencies of my 'app' module.