public void merge(ArtifactMetadata metadata) {
        ProjectArtifactMetadata m = (ProjectArtifactMetadata) metadata;
        if (!m.file.equals(file)) {
            throw new IllegalStateException("Cannot add two different pieces of metadata for: " + getKey());
        }
    }

    public void merge(org.apache.maven.repository.legacy.metadata.ArtifactMetadata metadata) {
        this.merge((ArtifactMetadata) metadata);
    }