metainfo: Clarify requirements, types

[madig]

• ufoLib requires only formatVersion
• version numbers should logically be non-negative.

[benkiel]

Hesitant to change the creator requirement (think that ufoLib should be fixed?). I see great value in knowing what produced the ufo. Other changes are good, of course. Open to other opinions on creator (@typesupply @miguelsousa @typemytype @anthrotype)

[typesupply]

What is the rationale for making the creator optional? I'm not arguing against it, just gathering info. The rationale for it being required was for debugging and the kinds of error correction that might be necessary for environment specific file structure mistakes. I have a vague memory of a non-ufoLib writer using the ufoLib creator signature so maybe it's meaningless now.

[madig]

I merely adapted the spec to what ufoLib is doing (realpolitik) -- if you agree that actually ufoLib should be fixed, I'll drop the optionality.

[typesupply]

I merely adapted the spec to what ufoLib is doing (realpolitik)

Is ufoLib not outputting it all the time? (I haven't looked at how creator is handled in > 10 years.)

---

I've been giving it some thought... Let's make the creator optional and open an issue to consider deprecating it. It's a meaningless bit of data at this point. For example: if a UFO is created by ufoLib and then 1/2 of the files in it are updated by somethingElseLib, what should the creator be? It's just a bit of data that seemed like a good idea 20 years ago when UFOs were used primarily in import/export situations. It doesn't make sense in the atomic edit situations that are more common today.

[madig]

It is outputting it I think, but it doesn't read it.

Also, what about e.g. (ufo)normalizers when they rewrite UFOs?

[benkiel]

Per @typesupply's comment, I'm merging this and adding a item to deprecate it.