Enhance GitHub Actions workflow for benchmark results

- Updated permissions to allow opening pull requests in addition to pushing benchmark result branches.
- Modified the workflow to create a new branch for benchmark results and automatically open a pull request with a detailed summary of changes.
- Improved commit message generation based on the type of GitHub reference (tag or branch) to ensure clarity in versioning.
- Added checks to skip PR creation if there are no changes to commit, enhancing workflow efficiency.

Author: TKorr

.github/workflows/benchmarks.yml

@@ -23,7 +23,8 @@ env:
   RUST_BACKTRACE: 1
 
 permissions:
-  contents: write  # Needed to commit benchmark results
+  contents: write       # Needed to push benchmark result branches
+  pull-requests: write  # Needed to open PRs
 
 jobs:
   benchmark:
@@ -118,8 +119,25 @@ jobs:
           git config user.name "github-actions[bot]"
           git config user.email "github-actions[bot]@users.noreply.github.com"
 
-      - name: Commit and push results
+      - name: Commit results to a new branch and open PR
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
+          # Determine branch name and PR title
+          if [ "${{ github.ref_type }}" = "tag" ]; then
+            VERSION="${GITHUB_REF#refs/tags/}"
+            BRANCH="benchmark-results/${VERSION}"
+            PR_TITLE="benchmark: update results for ${VERSION}"
+            COMMIT_MSG="benchmark: update results for ${VERSION} [skip ci]"
+          else
+            BRANCH="benchmark-results/$(date -u +%Y-%m-%d)-${{ github.run_id }}"
+            PR_TITLE="benchmark: update results ($(date -u +%Y-%m-%d))"
+            COMMIT_MSG="benchmark: update results [skip ci]"
+          fi
+
+          # Create and switch to the new branch from the current HEAD
+          git checkout -b "$BRANCH"
+
           # Add generated files (force add since they're in .gitignore)
           git add -f docs/benchmarks/latest/
 
@@ -130,21 +148,36 @@ jobs:
 
           # Check if there are changes to commit
           if git diff --staged --quiet; then
-            echo "ℹ️ No changes to commit"
+            echo "ℹ️ No changes to commit — skipping PR creation"
             exit 0
           fi
 
-          # Create commit message
-          if [ "${{ github.ref_type }}" = "tag" ]; then
-            COMMIT_MSG="benchmark: update results for ${GITHUB_REF#refs/tags/} [skip ci]"
-          else
-            COMMIT_MSG="benchmark: update results [skip ci]"
-          fi
-
           git commit -m "$COMMIT_MSG"
-          git push
-
-          echo "✅ Pushed benchmark results"
+          git push origin "$BRANCH"
+          echo "✅ Pushed branch: $BRANCH"
+
+          # Determine base branch (main by default, or the tag's base branch)
+          BASE_BRANCH="${{ github.event.repository.default_branch }}"
+
+          # Open a PR
+          gh pr create \
+            --base "$BASE_BRANCH" \
+            --head "$BRANCH" \
+            --title "$PR_TITLE" \
+            --body "$(cat <<'EOF'
+          ## 📊 Benchmark Results
+
+          This PR was automatically generated by the [Benchmarks workflow](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}).
+
+          **Files updated:**
+          - `docs/benchmarks/latest/index.md`
+          - `docs/benchmarks/latest/charts.html`
+          - `docs/benchmarks/latest/results.json`
+
+          > ⚠️ **Note:** Benchmark results may vary on CI runners. For consistent measurements, use a dedicated benchmark machine.
+          EOF
+          )"
+          echo "✅ PR opened"
 
       - name: Create benchmark summary
         if: always()