docs: private String findMainFileFromSnapshotPrefix(final String prefix) {
  
          File[] files = null;
          if (snapshotsDirectory.exists() && snapshotsDirectory.isDirectory()) {
              files = snapshotsDirectory.listFiles(new FilenameFilter() {
                  @Override
                  public boolean accept(File dir, String name) {
                      return name.startsWith(prefix) && SNAPSHOT_XML.matcher(name).find();
                  }
  
              });
          }
  
          if (files == null || files.length == 0) {
              return null;
          } else if (files.length > 1) {
              throw ControllerLogger.ROOT_LOGGER.ambiguousConfigurationFiles(prefix, snapshotsDirectory, prefix);
          }
  
          String matchName = files[0].getName();
          return matchName.substring(TIMESTAMP_FORMAT.length());
      }