Add noop storage backend

This is sometimes useful when an update gets stuck because of some
bug in backup logic.

Note that you cannot restore from this backend because nothing is
saved.

src/storage/noop.js

@@ -0,0 +1,73 @@
+'use strict';
+
+exports = module.exports = {
+    backup: backup,
+    restore: restore,
+    copyBackup: copyBackup,
+    removeBackups: removeBackups,
+
+    backupDone: backupDone,
+
+    testConfig: testConfig
+};
+
+var assert = require('assert'),
+    debug = require('debug')('box:storage/noop');
+
+function backup(apiConfig, backupId, sourceDirectories, callback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof backupId, 'string');
+    assert(Array.isArray(sourceDirectories));
+    assert.strictEqual(typeof callback, 'function');
+
+    debug('backup: %s %j', backupId, sourceDirectories);
+
+    callback();
+}
+
+function restore(apiConfig, backupId, destination, callback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof backupId, 'string');
+    assert.strictEqual(typeof destination, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    debug('restore: %s %s', backupId, destination);
+
+    callback(new Error('Cannot restore from noop backend'));
+}
+
+function copyBackup(apiConfig, oldBackupId, newBackupId, callback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof oldBackupId, 'string');
+    assert.strictEqual(typeof newBackupId, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    debug('copyBackup: %s -> %s', oldBackupId, newBackupId);
+
+    callback();
+}
+
+function removeBackups(apiConfig, backupIds, callback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert(Array.isArray(backupIds));
+    assert.strictEqual(typeof callback, 'function');
+
+    debug('removeBackups: %j', backupIds);
+
+    callback();
+}
+
+function testConfig(apiConfig, callback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof callback, 'function');
+
+    callback();
+}
+
+function backupDone(backupId, appBackupIds, callback) {
+    assert.strictEqual(typeof backupId, 'string');
+    assert(Array.isArray(appBackupIds));
+    assert.strictEqual(typeof callback, 'function');
+
+    callback();
+}