@NotNull
  private TextFilePatch buildPatchHeading(@NotNull AirContentRevision beforeRevision,
                                          @NotNull AirContentRevision afterRevision) {
    TextFilePatch result = new TextFilePatch(afterRevision.getCharset(), afterRevision.getLineSeparator());
    setPatchHeading(result, beforeRevision, afterRevision);
    return result;
  }
@NotNull
  private TextFilePatch buildPatchHeading(@NotNull AirContentRevision beforeRevision,
                                          @NotNull AirContentRevision afterRevision)