code: async function getPkgReleases({ lookupName, registryUrls }) {
    const { registry, repository } = getRegistryRepository(
      lookupName,
      registryUrls
    );
    const tags = await getTags(registry, repository);
    if (!tags) {
      return null;
    }
    const releases = tags.map(version => ({ version }));
    const ret = {
      dockerRegistry: registry,
      dockerRepository: repository,
      releases,
    };
  
    const latestTag = tags.includes('latest') ? 'latest' : tags[tags.length - 1];
    const labels = await getLabels(registry, repository, latestTag);
    // istanbul ignore if
    if (labels && 'org.opencontainers.image.source' in labels) {
      ret.sourceUrl = labels['org.opencontainers.image.source'];
    }
    return ret;
  }
docs: /*
  docker.getPkgReleases
  
  A docker image usually looks something like this: somehost.io/owner/repo:8.1.0-alpine
  In the above:
  - 'somehost.io' is the registry
  - 'owner/repo' is the package name
  - '8.1.0-alpine' is the tag
  
  This function will filter only tags that contain a semver version