github actions: Trigger clk-rebase workflow when stable branches are updated

Use repository_dispatch to trigger clk-rebase.yml only when sync.yml
actually pushes updates to stable_* branches.

Author: bmastbergen

.github/workflows/clk-rebase.yml

@@ -1,9 +1,11 @@
 name: CLK Rebase
 on:
   workflow_dispatch:
+  repository_dispatch:
+    types:
+      - stable-branch-updated
   push:
     branches:
-      - stable_6.*.y
       - clk-rebase-ga
 
 jobs:
@@ -14,10 +16,9 @@ jobs:
       options: --cpus 8 --privileged
     env:
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      # For push events, use the branch that triggered the workflow
-      # For manual dispatch, default to stable_6.12.y
-      #STABLE_TRACKING_BRANCH: ${{ github.ref_name || 'stable_6.12.y' }}
-      STABLE_TRACKING_BRANCH: ${{ 'stable_6.12.y' }}
+      # For repository_dispatch events, use the branch from the payload
+      # For push/manual dispatch to clk-rebase-ga or workflow_dispatch, default to stable_6.18.y
+      STABLE_TRACKING_BRANCH: ${{ github.event.client_payload.branch || (startsWith(github.ref_name, 'stable_') && github.ref_name) || 'stable_6.18.y' }}
     steps:
       - name: Set version variables
         run: |

.github/workflows/sync.yml

@@ -54,7 +54,30 @@ jobs:
 
           git remote add upstream ${REMOTE}
           git fetch upstream --tags --quiet
+
+          # Check if rebase will make changes
+          BEFORE_SHA=$(git rev-parse HEAD)
           git rebase upstream/${REMOTE_BRANCH}
-          git push origin --follow-tags
+          AFTER_SHA=$(git rev-parse HEAD)
+
+          if [ "$BEFORE_SHA" != "$AFTER_SHA" ]; then
+            echo "Changes detected, pushing..."
+            git push origin --follow-tags
+            echo "CHANGES_PUSHED=true" >> $GITHUB_ENV
+          else
+            echo "No changes to push"
+            echo "CHANGES_PUSHED=false" >> $GITHUB_ENV
+          fi
+
+      - name: Trigger CLK rebase workflow
+        if: env.CHANGES_PUSHED == 'true' && startsWith(matrix.branch, 'stable_')
+        run: |
+          curl -L \
+            -X POST \
+            -H "Accept: application/vnd.github+json" \
+            -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            https://api.github.com/repos/${{ github.repository }}/dispatches \
+            -d "{\"event_type\":\"stable-branch-updated\",\"client_payload\":{\"branch\":\"${{ matrix.branch }}\"}}"