The previous implementation used int64 for both, which can be mixed up
easily. Using distinct types adds a layer of type safety checked by the
compiler.
* Add common chunker.
* add comment.
* use better config name.
* Add common chunk reader to s3.
* Add common chunk reader to git, gcs, circleci.
* revert gcs.
* revert gcs.
* fix chunker.
* revert gcs.
* update cancellablewrite.
* revert impl.
* update to remove totalsize.
* Fix my goof.
* Use unified struct in chunkreader.
* return err instead of logging and returning.
* rename error to err.
* only send single ChunkResult even if there is an error and chunkBytes.
* fix logic.
* Implement CommonSourceUnitUnmarshaller
* Add SourceUnitUnmarshaller to all sources using
All sources, with the exception of git, will use the CommonSourceUnit as
they only contain a single type of unit to scan.
* Fix method comments to adhere to Go's style guide
