@Override
  public boolean equals(Object obj) {
    if (obj instanceof DescriptorDigest) {
      return hash.equals(((DescriptorDigest) obj).hash);
    }

    return false;
  }
Two digest objects are equal if their digest strings are equal.
jib-core/src/main/java/com/google/cloud/tools/jib/api/DescriptorDigest.java