github actions: compare test results only against merged PRs

Previously the workflow compared test results against any successful run
targeting the same base branch. This could include experimental branches
that were never merged or PRs that were later rejected.

Now the comparison logic checks if each candidate run's PR was actually
merged before using it as a baseline. This ensures comparisons are made
against stable, merged code that made it into the base branch.

The workflow still falls back gracefully if no merged PRs are found
(comparison is skipped but PR creation proceeds).

Author: bmastbergen

.github/workflows/kernel-build-and-test-multiarch.yml

@@ -373,7 +373,7 @@ jobs:
         echo "base_branch=$BASE_BRANCH" >> $GITHUB_OUTPUT
         echo "Base branch for comparison: $BASE_BRANCH"
 
-    - name: Download baseline kselftest logs from last successful run targeting same base
+    - name: Download baseline kselftest logs from last merged PR targeting same base
       if: steps.base_branch.outputs.base_branch != ''
       env:
         GH_TOKEN: ${{ steps.generate_token_compare.outputs.token }}
@@ -382,11 +382,11 @@ jobs:
         BASE_BRANCH="${{ steps.base_branch.outputs.base_branch }}"
         CURRENT_RUN_ID="${{ github.run_id }}"
 
-        echo "Searching for baseline from last successful run targeting base branch: $BASE_BRANCH"
+        echo "Searching for baseline from last merged PR targeting base branch: $BASE_BRANCH"
         echo "Current run ID: $CURRENT_RUN_ID (will be excluded from search)"
 
         # Get last 50 successful workflow runs (cast a wider net to find PRs targeting this base)
-        # We need to check each run to see if it targets the same base branch
+        # We need to check each run to see if it targets the same base branch AND was merged
         SUCCESSFUL_RUNS=$(gh run list \
           --workflow kernel-build-and-test-multiarch.yml \
           --status success \
@@ -417,36 +417,51 @@ jobs:
 
           # Check if this run targets the same base branch
           if [ "$EXTRACTED_BASE" = "$BASE_BRANCH" ]; then
-            echo "Found candidate run $RUN_ID from branch $HEAD_BRANCH (targets: $BASE_BRANCH)"
-
-            # Get the most recent artifact with this name (in case of reruns/duplicates)
-            # gh run download always picks the first artifact, which may be from an incomplete run
-            ARTIFACT_ID=$(gh api "repos/${{ github.repository }}/actions/runs/$RUN_ID/artifacts" \
-              --jq ".artifacts[] | select(.name == \"kselftest-logs-${{ matrix.arch }}\" and .expired == false) | .id" \
-              | tail -1)
-
-            if [ -n "$ARTIFACT_ID" ]; then
-              echo "Downloading artifact ID $ARTIFACT_ID (most recent with name kselftest-logs-${{ matrix.arch }})"
-              mkdir -p output-previous
-              if gh api "repos/${{ github.repository }}/actions/artifacts/$ARTIFACT_ID/zip" > /tmp/baseline-artifact.zip 2>/dev/null && \
-                 unzip -q /tmp/baseline-artifact.zip -d output-previous 2>/dev/null; then
-                echo "Successfully downloaded baseline from run $RUN_ID (branch: $HEAD_BRANCH, created: $CREATED_AT)"
-                rm -f /tmp/baseline-artifact.zip
-                echo "BASELINE_RUN_ID=$RUN_ID" >> $GITHUB_ENV
-                echo "BASELINE_BRANCH=$HEAD_BRANCH" >> $GITHUB_ENV
-                exit 0
+            # Check if the PR from this branch was merged and actually targets the expected base branch
+            PR_INFO=$(gh pr list --head "$HEAD_BRANCH" --base "$BASE_BRANCH" --state merged --json number,mergedAt,baseRefName --jq '.[0]' 2>/dev/null || echo "")
+
+            if [ -n "$PR_INFO" ] && [ "$PR_INFO" != "null" ]; then
+              BASE_REF=$(echo "$PR_INFO" | jq -r '.baseRefName')
+              if [ -z "$BASE_REF" ] || [ "$BASE_REF" = "null" ] || [ "$BASE_REF" != "$BASE_BRANCH" ]; then
+                echo "Merged PR for branch $HEAD_BRANCH does not target expected base $BASE_BRANCH (actual base: ${BASE_REF:-unknown}), skipping run $RUN_ID"
+                continue
+              fi
+
+              PR_NUMBER=$(echo "$PR_INFO" | jq -r '.number')
+              MERGED_AT=$(echo "$PR_INFO" | jq -r '.mergedAt')
+              echo "Found merged PR #$PR_NUMBER from branch $HEAD_BRANCH (merged: $MERGED_AT, targets: $BASE_REF)"
+
+              # Get the most recent artifact with this name (in case of reruns/duplicates)
+              ARTIFACT_ID=$(gh api "repos/${{ github.repository }}/actions/runs/$RUN_ID/artifacts" \
+                --jq ".artifacts[] | select(.name == \"kselftest-logs-${{ matrix.arch }}\" and .expired == false) | .id" \
+                | tail -1)
+
+              if [ -n "$ARTIFACT_ID" ]; then
+                echo "Downloading artifact ID $ARTIFACT_ID (most recent with name kselftest-logs-${{ matrix.arch }})"
+                mkdir -p output-previous
+                if gh api "repos/${{ github.repository }}/actions/artifacts/$ARTIFACT_ID/zip" > /tmp/baseline-artifact.zip 2>/dev/null && \
+                   unzip -q /tmp/baseline-artifact.zip -d output-previous 2>/dev/null; then
+                  echo "Successfully downloaded baseline from merged PR #$PR_NUMBER (run $RUN_ID, branch: $HEAD_BRANCH)"
+                  rm -f /tmp/baseline-artifact.zip
+                  echo "BASELINE_RUN_ID=$RUN_ID" >> $GITHUB_ENV
+                  echo "BASELINE_BRANCH=$HEAD_BRANCH" >> $GITHUB_ENV
+                  echo "BASELINE_PR=$PR_NUMBER" >> $GITHUB_ENV
+                  exit 0
+                else
+                  echo "Failed to download or extract artifact $ARTIFACT_ID"
+                  rm -f /tmp/baseline-artifact.zip
+                fi
               else
-                echo "Failed to download or extract artifact $ARTIFACT_ID"
-                rm -f /tmp/baseline-artifact.zip
+                echo "Run $RUN_ID has no kselftest artifacts for ${{ matrix.arch }} or they expired"
               fi
             else
-              echo "Run $RUN_ID has no kselftest artifacts for ${{ matrix.arch }} or they expired"
+              echo "Branch $HEAD_BRANCH was not merged, skipping run $RUN_ID"
             fi
           fi
         done < <(echo "$SUCCESSFUL_RUNS" | jq -c '.[]')
 
-        echo "::warning::No baseline test results found in recent successful runs targeting $BASE_BRANCH"
-        echo "::notice::This may be the first run targeting this base branch, or artifacts have expired (7-day retention)"
+        echo "::warning::No baseline test results found from merged PRs targeting $BASE_BRANCH"
+        echo "::notice::This may be the first merged PR targeting this base branch, or artifacts have expired (7-day retention)"
       continue-on-error: true
       timeout-minutes: 3