message: method to revert the engine to previous state
diff: @@ -10,7 +10,7 @@ export class ContribInstallController {
  this.installState = INTSTALLATION_STATE.INIT;
  }
  - installContribution(urls) {
  + installContributions(urls) {
  let installResults;
  return this.createBackup()
  .then(() => this.installToEngine(urls))
  @@ -69,6 +69,20 @@ export class ContribInstallController {
  }
  }
  + backupSource() {
  + console.log('[Log] Recovering engine to previous working state.');
  + return new Promise((resolve, reject) => {
  + const srcPath = path.join(this.testEngine.path, 'backupsrc');
  + if (fileExists(srcPath)) {
  + copyFile(srcPath, path.join(this.testEngine.path, 'src'))
  + .then(() => resolve(true))
  + .catch((error) => reject(error));
  + } else {
  + resolve(true);
  + }
  + });
  + }
  +
  installToEngine(urls) {
  this.installState = INTSTALLATION_STATE.INSTALL;
  return this.remoteInstaller.install(urls, {engine: this.testEngine});
  