public Optional<CachedLayer> retrieveTarLayer(DescriptorDigest diffId)
      throws IOException, CacheCorruptedException {
    return cacheStorageReader.retrieveTarLayer(diffId);
  }
Retrieves a {@link CachedLayer} for a local base image layer with the given diff id.

@param diffId the diff id
@return the {@link CachedLayer} with the given diff id
@throws CacheCorruptedException if the cache was found to be corrupted
@throws IOException if an I/O exception occurs
jib-core/src/main/java/com/google/cloud/tools/jib/cache/Cache.java