code: func (pmc *proxyMetricsCollector) ManifestPush(bytesPushed uint64) {
  	atomic.AddUint64(&pmc.manifestMetrics.Requests, 1)
  	atomic.AddUint64(&pmc.manifestMetrics.Hits, 1)
  	atomic.AddUint64(&pmc.manifestMetrics.BytesPushed, bytesPushed)
  }
docs: // ManifestPush tracks metrics about manifests pushed to clients