Update base commit of code coverage (#8316)

The code coverage is comparing a merge commit to the common commit of a PR and the target branch. This will involve changes between this common commit and the latest commit of the target branch. This update will switch the common commit of the PR to the latest commit on the target branch.

Author: granluo

.github/workflows/test_coverage.yml

@@ -39,7 +39,7 @@ jobs:
           pr_branch: ${{ github.event.pull_request.head.ref }}
         run: |
           if [ ! -z "${{ env.METRICS_SERVICE_SECRET }}"  ]; then
-          ./scripts/code_coverage_report/get_updated_files.sh
+            ./scripts/code_coverage_report/get_updated_files.sh
           fi
 
   pod-lib-lint-abtesting:
@@ -282,13 +282,12 @@ jobs:
       - name: Compare Diff and Post a Report
         if: github.event.pull_request.merged != true && github.event.action != 'closed' && env.METRICS_SERVICE_SECRET != ''
         env:
-          base_commit: ${{ needs.check.outputs.base_commit }}
+          base_commit: ${{ ${{ github.event.pull_request.base.sha }} }}
         run: |
           # Get Head commit of the branch, instead of a merge commit created by actions/checkout.
-          GITHUB_SHA=$(cat $GITHUB_EVENT_PATH | jq -r .pull_request.head.sha)
           if [ -d "${{steps.download.outputs.download-path}}" ]; then
-          cd scripts/code_coverage_report/generate_code_coverage_report
-          swift run CoverageReportGenerator --presubmit "firebase/firebase-ios-sdk" --head-commit "${GITHUB_SHA}" --token $(gcloud auth print-identity-token) --xcresult-dir "/Users/runner/test/codecoverage" --log-link "https://github.com/firebase/firebase-ios-sdk/actions/runs/${GITHUB_RUN_ID}" --pull-request-num ${{github.event.pull_request.number}} --base-commit "$base_commit"
+            cd scripts/code_coverage_report/generate_code_coverage_report
+            swift run CoverageReportGenerator --presubmit "firebase/firebase-ios-sdk" --head-commit "${GITHUB_SHA}" --token $(gcloud auth print-identity-token) --xcresult-dir "/Users/runner/test/codecoverage" --log-link "https://github.com/firebase/firebase-ios-sdk/actions/runs/${GITHUB_RUN_ID}" --pull-request-num ${{github.event.pull_request.number}} --base-commit "$base_commit"
           fi
       - name: Incremental Code Coverage
         if: github.event.pull_request.merged != true && github.event.action != 'closed'
@@ -319,6 +318,6 @@ jobs:
         if: github.event.pull_request.merged && env.METRICS_SERVICE_SECRET != ''
         run: |
           if [ -d "${{steps.download.outputs.download-path}}" ]; then
-          cd scripts/code_coverage_report/generate_code_coverage_report
-          swift run CoverageReportGenerator --merge "firebase/firebase-ios-sdk" --head-commit "${GITHUB_SHA}" --token $(gcloud auth print-identity-token) --xcresult-dir "/Users/runner/test/codecoverage" --log-link "https://github.com/firebase/firebase-ios-sdk/actions/runs/${GITHUB_RUN_ID}" --source-branch "${{ github.base_ref }}"
+            cd scripts/code_coverage_report/generate_code_coverage_report
+            swift run CoverageReportGenerator --merge "firebase/firebase-ios-sdk" --head-commit "${GITHUB_SHA}" --token $(gcloud auth print-identity-token) --xcresult-dir "/Users/runner/test/codecoverage" --log-link "https://github.com/firebase/firebase-ios-sdk/actions/runs/${GITHUB_RUN_ID}" --source-branch "${{ github.base_ref }}"
           fi