Apply libyaml upstream changes

[inteon]

depends on #95

Apply the missing changes from upstream libyaml (see commit messages for individual changes). Additionally, in c47598a, I fixed the yts tests that started failing (on master, they were passing for the wrong reasons).

Upstream commits:

• yaml/libyaml@9afa10a
• yaml/libyaml@fa1293a
• yaml/libyaml@3d5b7e6
• yaml/libyaml@4e5cea6
• yaml/libyaml@3694a4a
• yaml/libyaml@f41d360
• yaml/libyaml@6e2fa97
• yaml/libyaml@7eb0197
• yaml/libyaml@1008696
• yaml/libyaml@588eabf
• yaml/libyaml@840b65c

[ccoVeille]

Apply the missing changes from upstream libyaml (see commit messages for individual changes). Additionally, in c47598a, I fixed the yts tests that started failing (on master, they were passing for the wrong reasons).

Impressive, thank you so much.

[Copilot]

Pull Request Overview

This PR applies upstream changes from libyaml to the Go YAML library, incorporating multiple bug fixes and feature updates from the C library. The changes primarily focus on improving YAML parsing, validation, and emission behavior to align with upstream standards.

Key changes include:

• Added support for YAML version 1.2 directives alongside the existing 1.1 support
• Fixed parser state management for flow sequences and document handling
• Updated scanner logic for tag URIs and plain scalars to be more restrictive and correct

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
yts/known-failing-tests	Removed test cases that now pass due to upstream fixes
yamlh.go	Added version directive tracking and end type enumeration for better document state management
scannerc.go	Updated tag URI scanning logic and fixed plain scalar parsing restrictions
parserc.go	Enhanced version directive support and improved flow sequence parsing
encode.go	Updated to use new end type enumeration
emitterc.go	Comprehensive updates to document emission logic and YAML version handling

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[ingydotnet]

@inteon Thanks for this. I amended each of your commits (and pushed them back to you) to add URLs pointing back to the libyaml commits to make it easier for people to review.

I still need to review.

[ingydotnet]

FWIW, go-yaml was ported from libyaml which was ported from pyyaml.
All of these are under the github.com/yaml org.

A goal of the org and this project is to see them all come into sync.
Also to identify all the most popular ports out there and to add supported forks to the yaml org, or submit patches to them.

It would be good to have tools to identify the current state of these things.

[dolmen]

I can't review all at once: comparing each Go commit to libyaml is an important effort. I would prefer separate PR for each.
So I'll skip that one.

[ingydotnet]

I can't review all at once: comparing each Go commit to libyaml is an important effort. I would prefer separate PR for each. So I'll skip that one.

This is fair.

@inteon Would you mind turning one or two of these commits into their own PR with one commit for each?

You could do all of them but I don't want to waste your time if there ends up being a problem with all of them.

Also could you copy the original merged libyaml PR text into the new PR? I know we have links to them, but probably better to have the text right there...

Love this work btw!