fix(ci-insights): Use GITHUB_HEAD_REF instead of GITHUB_REF_NAME (#355)

`GITHUB_REF_NAME` contains `<pr_number>/merge` in pull request contexts instead
of the original branch name. `GITHUB_HEAD_REF` provides the actual source
branch name for pull requests. See: github/docs#15319

Since `GITHUB_HEAD_REF` is only set for PR events, we fall back to
`GITHUB_REF_NAME` o ensure branch detection keeps working in all contexts.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: remyduthu

pytest_mergify/resources/github_actions.py

@@ -26,6 +26,13 @@ def _get_repository_url() -> typing.Optional[str]:
     return None
 
 
+def _get_head_ref_name() -> typing.Optional[str]:
+    # `GITHUB_HEAD_REF` contains the actual branch name for PRs, while
+    # `GITHUB_REF_NAME` contains `<pr_number>/merge`. However, `GITHUB_HEAD_REF`
+    # is only set for PR events, so we fall back to `GITHUB_REF_NAME`.
+    return os.getenv("GITHUB_HEAD_REF") or os.getenv("GITHUB_REF_NAME")
+
+
 class GitHubActionsResourceDetector(ResourceDetector):
     """Detects OpenTelemetry Resource attributes for GitHub Actions."""
 
@@ -35,7 +42,7 @@ class GitHubActionsResourceDetector(ResourceDetector):
         cicd_attributes.CICD_PIPELINE_RUN_ID: (int, "GITHUB_RUN_ID"),
         "cicd.pipeline.run.attempt": (int, "GITHUB_RUN_ATTEMPT"),
         "cicd.pipeline.runner.name": (str, "RUNNER_NAME"),
-        vcs_attributes.VCS_REF_HEAD_NAME: (str, "GITHUB_REF_NAME"),
+        vcs_attributes.VCS_REF_HEAD_NAME: (str, _get_head_ref_name),
         vcs_attributes.VCS_REF_HEAD_TYPE: (str, "GITHUB_REF_TYPE"),
         vcs_attributes.VCS_REF_BASE_NAME: (str, "GITHUB_BASE_REF"),
         "vcs.repository.name": (str, "GITHUB_REPOSITORY"),

tests/test_ci_insights.py

@@ -27,12 +27,13 @@ def _set_test_environment(
     monkeypatch.setenv("MERGIFY_TOKEN", "my_token")
 
     if mode == "unhealthy":
-        # Simulate absence of a PR context: without `GITHUB_BASE_REF` and
-        # `GITHUB_REF_NAME` `MergifyCIInsights.branch_name` can't be derived,
+        # Simulate absence of a PR context: without `GITHUB_BASE_REF` and branch
+        # ref variables, `MergifyCIInsights.branch_name` can't be derived,
         # forcing the flaky detector to fall back to `unhealthy` mode. This
         # explicitly exercises the fallback path used when no PR metadata is
         # available.
         monkeypatch.delenv("GITHUB_BASE_REF", raising=False)
+        monkeypatch.delenv("GITHUB_HEAD_REF", raising=False)
         monkeypatch.delenv("GITHUB_REF_NAME", raising=False)
 
 

tests/test_resources.py

@@ -5,6 +5,7 @@
 import pytest
 
 from pytest_mergify import utils
+from pytest_mergify.resources import github_actions
 from tests import conftest
 
 
@@ -78,6 +79,32 @@ def test_span_github_actions(
     )
 
 
+@pytest.mark.parametrize(
+    ("head_ref", "ref_name", "expected"),
+    [
+        pytest.param("feature-branch", "123/merge", "feature-branch", id="PR context"),
+        pytest.param(None, "main", "main", id="Without `GITHUB_REF_NAME`"),
+        pytest.param("", "main", "main", id="Empty `GITHUB_REF_NAME`"),
+        pytest.param(None, None, None, id="Without any variable"),
+    ],
+)
+def test_get_head_ref_name(
+    monkeypatch: pytest.MonkeyPatch,
+    head_ref: typing.Optional[str],
+    ref_name: typing.Optional[str],
+    expected: typing.Optional[str],
+) -> None:
+    monkeypatch.delenv("GITHUB_HEAD_REF", raising=False)
+    monkeypatch.delenv("GITHUB_REF_NAME", raising=False)
+
+    if head_ref:
+        monkeypatch.setenv("GITHUB_HEAD_REF", head_ref)
+    if ref_name:
+        monkeypatch.setenv("GITHUB_REF_NAME", ref_name)
+
+    assert github_actions._get_head_ref_name() == expected
+
+
 @mock.patch("pytest_mergify.utils.git", return_value=None)
 def test_span_jenkins(
     git: mock.Mock,