public HistoryEntry build() {
      return new HistoryEntry(
          creationTimestamp == null ? null : creationTimestamp.toString(),
          author,
          createdBy,
          comment,
          emptyLayer);
    }
Create a new history entry.

@return an new {@link HistoryEntry} instance
jib-core/src/main/java/com/google/cloud/tools/jib/image/json/HistoryEntry.java