code: public List<I_CmsHistoryResource> readAllAvailableVersions(CmsRequestContext context, CmsResource resource)
      throws CmsException {
  
          List<I_CmsHistoryResource> result = null;
          CmsDbContext dbc = m_dbContextFactory.getDbContext(context);
          try {
              result = m_driverManager.readAllAvailableVersions(dbc, resource);
          } catch (Exception e) {
              dbc.report(
                  null,
                  Messages.get().container(Messages.ERR_READ_ALL_HISTORY_FILE_HEADERS_1, context.getSitePath(resource)),
                  e);
          } finally {
              dbc.clear();
          }
          return result;
      }
docs: Reads all historical versions of a resource.<p>
  
  The reading excludes the file content, if the resource is a file.<p>
  
  @param context the current request context
  @param resource the resource to be read
  
  @return a list of historical versions, as <code>{@link I_CmsHistoryResource}</code> objects
  
  @throws CmsException if something goes wrong