code: public synchronized Project purgeProject(final Project project, final User deleter)
        throws ProjectManagerException {
      this.projectLoader.cleanOlderProjectVersion(project.getId(),
          project.getVersion() + 1, Collections.emptyList());
      this.projectLoader
          .postEvent(project, EventType.PURGE, deleter.getUserId(), String
              .format("Purged versions before %d", project.getVersion() + 1));
      return project;
    }
docs: Permanently delete all project files and properties data for all versions of a project and log
  event in project_events table