@Nullable
  @Override
  protected VcsFileRevision getFileRevision(@NotNull AnActionEvent e) {
    VcsHistorySession historySession = e.getData(VcsDataKeys.HISTORY_SESSION);
    if (historySession == null) return null;

    VcsFileRevision revision = e.getData(VcsDataKeys.VCS_FILE_REVISION);
    if (!historySession.isContentAvailable(revision)) return null;

    return revision;
  }
@Nullable
  @Override
  protected VcsFileRevision getFileRevision(@NotNull AnActionEvent e)