@Override
  public int hashCode() {
    return Objects.hash(author, creationTimestamp, createdBy, comment, emptyLayer);
  }
Returns whether or not the history object corresponds to a layer in the container.

@return {@code true} if the history object corresponds to a layer in the container
jib-core/src/main/java/com/google/cloud/tools/jib/image/json/HistoryEntry.java