feat: export head sha (#52)

pytest_mergify/resources/github_actions.py

@@ -1,4 +1,6 @@
 import os
+import pathlib
+import json
 
 from opentelemetry.sdk.resources import Resource, ResourceDetector
 
@@ -11,6 +13,18 @@
 class GitHubActionsResourceDetector(ResourceDetector):
     """Detects OpenTelemetry Resource attributes for GitHub Actions."""
 
+    @staticmethod
+    def get_github_actions_head_sha() -> str | None:
+        if os.getenv("GITHUB_EVENT_NAME") == "pull_request":
+            # NOTE: we want the head sha of the pull request
+            event_raw_path = os.getenv("GITHUB_EVENT_PATH")
+            if event_raw_path and (
+                (event_path := pathlib.Path(event_raw_path)).is_file()
+            ):
+                event = json.loads(event_path.read_bytes())
+                return str(event["pull_request"]["head"]["sha"])
+        return os.getenv("GITHUB_SHA")
+
     OPENTELEMETRY_GHA_MAPPING = {
         cicd_attributes.CICD_PIPELINE_NAME: "GITHUB_JOB",
         cicd_attributes.CICD_PIPELINE_RUN_ID: "GITHUB_RUN_ID",
@@ -33,6 +47,10 @@ def detect(self) -> Resource:
                 os.environ["GITHUB_SERVER_URL"] + "/" + os.environ["GITHUB_REPOSITORY"]
             )
 
+        head_sha = self.get_github_actions_head_sha()
+        if head_sha is not None:
+            attributes[vcs_attributes.VCS_REF_HEAD_REVISION] = head_sha
+
         for attribute_name, envvar in self.OPENTELEMETRY_GHA_MAPPING.items():
             if envvar in os.environ:
                 attributes[attribute_name] = os.environ[envvar]