list-unicodeset: document Unicode version syntax

[markusicu]

I was just trying to use the list-unicodeset utility with the set of new-in-Unicode 17 characters in issue #982. The utility is still on Unicode 16, so then I tried to group characters by U17:gc guessing & hoping that that would show the draft values. No effect.

The help page does not mention the versioned-property syntax: https://unicode-org.github.io/unicodetools/help/list-unicodeset

Could someone please document that?

@eggrobin @macchiati

[eggrobin]

I tried to group characters by U17:gc guessing & hoping that that would show the draft values. No effect.

The tools haven’t been pushed since shortly after the 16.0 release, so you’re unlikely to see anything. U17dev: should work.

Could someone please document that?

My plan is to stick that in the forthcoming UnicodeSet spec (as an extension; obviously I don’t want to require ICU to support that, but we should make sure it is reserved so that it is either an error or means what it does in the tools, and the notation could come in handy when talking about properties).

In the meantime, there is this thing: https://github.com/unicode-org/unicodetools/blob/8459b0b27f09eeec411252d214cb7e2fd47fdd45/docs/help/changes.md