"Split" package content upload/download

[lann]

As discussed in the meeting, we'd like to support splitting components into multiple files to enable deduplication of content. The proposed mechanism of a content-addressed implementation import type covers the representation, but we still need to think through the implications for the content upload and download protocols.

For upload, we may be able to make things work by tweaking the semantics of the existing message schema to allow new entries to be added to the missing_content section during the sourcing phase after all initial (root) content has been uploaded. A publisher would need to continue polling and uploading content until the sourcing phase is over.

For download, some options that come to mind:

• We could include any "child" content in the content_sources section, plus one of:
  • leave it up to the client to inspect the root component and come back to fetch child content
  • add a new e.g. child_contents section listing child content for each root component
• We could say that download of multiple files is a concern of specific content_sources:
  • OCI natively supports download of multiple bits of content
  • A simple HTTP content source could perhaps include a set of URLs covering both root and child content