fix(gha): set vcs.ref.head.name correctly on PR

[jd]

For pull requests, this is not set to the head branch but to pull/XX

[mergify]

Merge Protections

Your pull request matches the following merge protections and will not be merged until they are valid.

🟢 Approval

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• #approved-reviews-by >= 1

🟢 Continuous Integration

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• all of:
  • check-success = test (3.10)
  • check-success = test (3.11)
  • check-success = test (3.12)
  • check-success = test (3.13)

🟢 Changelog requirements

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• any of:
  • -title ~= ^feat
  • label = need changelog
  • label = skip changelog

🟢 Enforce conventional commit

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Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?:

🟢 🔎 Reviews

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• #changes-requested-reviews-by = 0
• #review-requested = 0
• #review-threads-unresolved = 0