* Add common chunker. * add comment. * use better config name. * Add common chunk reader to s3. * Add common chunk reader to git, gcs, circleci. * fix chunker. * revert gcs. * update cancellablewrite. * revert impl. * update to remove totalsize.
* Add CancellableWrite helper function * Create SourceUnitEnumerator interface and EnumerationResult struct * Implement SourceUnitEnumerator for the filesystem Source * Omit explicit zero values