private void showDiffForMergeCommit(final @NotNull AnActionEvent event, final @NotNull FilePath filePath,
                                      final @NotNull GitFileRevision rev, final @NotNull Collection<String> parents) {
    VcsHistorySession session = event.getData(VcsDataKeys.HISTORY_SESSION);
    List<VcsFileRevision> revisions = session != null ? session.getRevisionList() : null;
    checkIfFileWasTouchedAndFindParentsInBackground(filePath, rev, parents, revisions, info -> {
      if (!info.wasFileTouched()) {
        String message = GitBundle.message("git.history.diff.handler.no.changes.in.file.info", filePath.getName());
        VcsBalloonProblemNotifier.showOverVersionControlView(this.myProject, message, MessageType.INFO);
      }
      showPopup(event, rev, filePath, info.getParents());
    });
  }
private void showDiffForMergeCommit(final @NotNull AnActionEvent event, final @NotNull FilePath filePath,
                                      final @NotNull GitFileRevision rev, final @NotNull Collection<String> parents)