chore(ci_visibility): fix github actions pr base sha

[gnufede]

PR by Bits
View session in Datadog

Comment @DataDog to request changes

Feedback (especially what can be better) welcome in #code-gen-aka-bits-dev-feedback!

---

Description

• Update GitHub Actions CI metadata to capture PR base branch head SHA separately and compute merge-base SHA for PR diffs (SDTEST-2356)
• Add GitHub Actions PR tags for base/head commit details and adjust test coverage for the new metadata

Testing

• Not run (hatch run lint:fmt -- ddtrace/ext/git.py ddtrace/ext/ci.py ddtrace/testing/internal/git.py ddtrace/testing/internal/ci.py tests/tracer/test_ci.py tests/testing/internal/test_env_tags.py failed: network resolution error while creating hatch environment)

Risks

• Low (metadata tag changes for GitHub Actions PRs)

Additional Notes

• Formatting could not be verified because hatch attempted to download a Python distribution and failed without network access

[datadog-datadog-prod-us1]

[View session in Datadog]

Bits Dev status: ✅ Done

CI Auto-fix: Enabled | Disable

Comment @DataDog to request changes

[cit-pr-commenter-54b7da]

Codeowners resolved as

releasenotes/notes/fix-gh-actions-pr-base-sha-90b1e2f89d0d6f3a.yaml     @DataDog/apm-python