use COVERALLS_GIT_BRANCH like documented in their npm package readme

erdii · erdii · commit 81ab0667af6d · 2020-06-06T20:15:56.000+02:00
- example from https://www.npmjs.com/package/coveralls
diff --git a/.github/workflows/node.js.yml b/.github/workflows/node.js.yml
@@ -36,5 +36,5 @@ jobs:
         COVERALLS_REPO_TOKEN: ${{ secrets.COVERALLS_REPO_TOKEN }}
         COVERALLS_SERVICE_NAME: "gh-actions"
         COVERALLS_SERVICE_NUMBER: "${{ github.run_id }}:${{ github.run_number }}"
-        COVERALLS_GIT_BRANCH: ${{ steps.extract_branch.outputs.branch }}
+        COVERALLS_GIT_BRANCH: ${{ github.ref }}
         COVERALLS_PARALLEL: "true"
