@Nullable
  private TextFilePatch buildModifiedFile(@NotNull AirContentRevision beforeRevision,
                                          @NotNull AirContentRevision afterRevision) throws VcsException {
    String beforeContent = beforeRevision.getContentAsString();
    String afterContent = afterRevision.getContentAsString();

    TextFilePatch patch = buildPatchHeading(beforeRevision, afterRevision);

    List<PatchHunk> hunks = buildPatchHunks(beforeContent, afterContent, myContextLineCount);
    for (PatchHunk hunk : hunks) {
      patch.addHunk(hunk);
    }

    // skip empty patch
    if (hunks.isEmpty() && beforeRevision.getPath().equals(afterRevision.getPath())) return null;

    return patch;
  }
@Nullable
  private TextFilePatch buildModifiedFile(@NotNull AirContentRevision beforeRevision,
                                          @NotNull AirContentRevision afterRevision)