Fix benchmark PR workflow

Author: pflooky

.github/workflows/benchmark.yml

@@ -29,19 +29,32 @@ jobs:
       (github.event.workflow_run.conclusion == 'success' &&
        github.event.workflow_run.event == 'push')
     steps:
-      - name: Get branch name
+      - name: Get branch and checkout ref
         id: branch
         run: |
           if [ "${{ github.event_name }}" == "workflow_dispatch" ]; then
-            echo "name=${{ github.ref_name }}" >> $GITHUB_OUTPUT
+            # For manual trigger, use the current branch for both
+            echo "base_branch=${{ github.ref_name }}" >> $GITHUB_OUTPUT
+            echo "checkout_ref=${{ github.ref_name }}" >> $GITHUB_OUTPUT
           else
-            echo "name=${{ github.event.workflow_run.head_branch }}" >> $GITHUB_OUTPUT
+            # For workflow_run trigger, get the head branch
+            head_branch="${{ github.event.workflow_run.head_branch }}"
+            # If the head_branch looks like a tag (matches semantic version pattern),
+            # use main as the base branch for the PR but checkout from main
+            if [[ "$head_branch" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+              echo "Detected tag: $head_branch, using 'main' as base branch"
+              echo "base_branch=main" >> $GITHUB_OUTPUT
+              echo "checkout_ref=main" >> $GITHUB_OUTPUT
+            else
+              echo "base_branch=$head_branch" >> $GITHUB_OUTPUT
+              echo "checkout_ref=$head_branch" >> $GITHUB_OUTPUT
+            fi
           fi
       - name: Checkout monorepo
         uses: actions/checkout@v4
         with:
           # Checkout the branch, not the commit, to avoid detached HEAD
-          ref: ${{ steps.branch.outputs.name }}
+          ref: ${{ steps.branch.outputs.checkout_ref }}
           fetch-depth: 2
       - name: Determine version to benchmark
         id: benchmark_version
@@ -122,5 +135,5 @@ jobs:
 
             Triggered by: ${{ github.event_name }}
           branch: benchmark-results-${{ steps.benchmark_version.outputs.value }}
-          base: ${{ steps.branch.outputs.name }}
+          base: ${{ steps.branch.outputs.base_branch }}
           commit-message: Add benchmark results for version ${{ steps.benchmark_version.outputs.value }}