Auto set automerge HEAD and BASE

Signed-off-by: Peixin Li <[email protected]>

.github/workflows/auto-merge.yml

@@ -18,25 +18,57 @@ name: auto-merge HEAD to BASE
 on:
   pull_request_target:
     branches:
-      - branch-24.08
+      - branch-*
     types: [closed]
 
-env:
-  HEAD: branch-24.08
-  BASE: branch-24.10
-
 jobs:
-  auto-merge:
+  auto-merge: # TODO: use spark-rapids-common shared action when available
     if: github.event.pull_request.merged == true
     runs-on: ubuntu-latest
 
     steps:
+      - name: set HEAD ENV
+        run: echo "HEAD=${{ github.event.pull_request.base.ref }}" >> $GITHUB_ENV
+
+      - name: Generate target branch
+        run: |
+          current_branch="${{ env.HEAD }}"
+          version=${current_branch#branch-}
+
+          IFS='.' read -r -a parts <<< "$version"
+          year=${parts[0]}
+          month=${parts[1]}
+          month=$((10#$month + 2))
+          if [ $month -gt 12 ]; then
+            month=$((month - 12))
+            year=$((year + 1))
+          fi
+
+          next_release=$(printf "%02d.%02d" $year $month)
+          echo "Next release is $next_release"
+          echo "BASE=branch-$next_release" >> $GITHUB_ENV
+
+      - name: Check if target branch exists
+        run: |
+          CODE=$(curl -s -o /dev/null -w "%{http_code}" -H "Authorization: token ${{ secrets.AUTOMERGE_TOKEN }}" \
+            https://api.github.com/repos/${{ github.repository }}/branches/${{ env.BASE }})
+          echo "Response code: $CODE..."
+
+          if [ $CODE -eq 200 ]; then
+            echo "branch_exists=true" >> $GITHUB_ENV
+          else
+            echo "branch_exists=false" >> $GITHUB_ENV
+            echo "Failed to find ${{ env.BASE }}. Skip auto-merge..."
+          fi
+
       - uses: actions/checkout@v4
+        if: env.branch_exists == 'true'
         with:
           ref: ${{ env.HEAD }} # force to fetch from latest upstream instead of PR ref
           token: ${{ secrets.AUTOMERGE_TOKEN }} # workaround auto-merge token to avoid GITHUB_TOKEN insufficient permission
 
       - name: push intermediate branch for auto-merge
+        if: env.branch_exists == 'true'
         run: |
           git config user.name "spark-rapids automation"
           git config user.email "[email protected] "
@@ -55,6 +87,7 @@ jobs:
           FILE_USE_BASE: thirdparty/cudf thirdparty/cudf-pins
 
       - name: auto-merge job
+        if: env.branch_exists == 'true'
         uses: ./.github/workflows/action-helper
         with:
           operator: auto-merge
@@ -64,4 +97,3 @@ jobs:
           HEAD: bot-auto-merge-${{ env.HEAD }}
           BASE: ${{ env.BASE }}
           TOKEN: ${{ secrets.AUTOMERGE_TOKEN }}
-