Link to Roadmap.md with more details.

TLDR: There are situations where the original imported/fecthed document should be push/exported without changes.

We currently save off the original document (as a string) and document format as unique annotations in the DB. It should only be a matter of checking these fields upon export/push to see if the desired format is the same as the original format and if it is use the original document string in lieu of protobom document.

SInce this may be mainly a signature preservation issue, maybe a flag like preserve-signatures would push it as the origin document without additional flags. Would also work in situations where the original format is not readily known.