Attempt to use common trait between variants

[michalfita]

Important

This is in the ideation stage, not supposed to be merged without any real life proof of sense.

I made attempt to create a trait shared between lossy and lossless variants of Repository, but this has following flaws:

• Interface over lossy variant works nice as we can refer to member; I tried Cow<> but now dealing with fact Paragraph::get() may fail become a problem (unwrap() is plain wrong).
• Use Cow<> is going to work for some cases, but may be a problem for some others, especially if wrapped in Option<>
• For optional fields use of .ok() turns potential errors of late parsing into None, I have doubts if it's acceptable.

Problems with lossless structure:

• Paragraphs are copied out of Deb822, there's not reference to them
• If lossless::Repositories store Deb822, I can only create lossless::Repository from these paragraphs, there's not way to return reference to them (that's different than in lossy variant).

Maybe I'm heading in wrong direction (no modifications/setting taken into account yet), as this route gives me identical API of both variants, but with problems. Maybe the role of lossless variant should be to produce out lossy variant and accept one to perform modifications.

Can we discuss pros and cons?

[jelmer]

Hey, this is still marked as draft - is this ready?

[michalfita]

Simple answer is: somehow.
Explanation: I stuck with Signature and reference to it via Cow<> (or not). It happen when my time on this has ended, so the PR doesn't even have my latest changes with more tests and examples. As I progressed with testing I had to amend synopses to actually make sens for users. I'd like to finish this, but ATM I can't give any promises - this is currently only a side hustle (even if derived from work I did for work).
As unhappy as I am I have to say patience required. This was more mentally consuming that I initially anticipated, but I believe I cooked something interesting here.

[michalfita]

OK, I pushed my latest state of unfinished work. It can get rough review about the idea and the premise, but it's not in the mergeable state yet.