Apply workaround from actions/toolkit#1264 to find workflow ref

.github/workflows/assemble_multiarch_image.yaml

@@ -21,23 +21,37 @@ jobs:
     name: Create Mulitarch Manifest
     runs-on: ubuntu-22.04
     steps:
-    - name: Get Workflow Reference
-      id: workflow-ref
+    - name: Checkout calling repository
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 1
+
+    - name: Get workflow reference
+      id: workflows-ref
       run: |
-        if [ -n "${{ github.workflow_ref }}" ]; then
-          IFS='@' read -r WORKFLOW_REPO WORKFLOW_REF << ${{ github.workflow_ref }}
-          echo "WORKFLOW_REPO=$WORKFLOW_REPO" >> $GITHUB_ENV
-          echo "WORKFLOW_REF=$WORKFLOW_REF" >> $GITHUB_ENV
-        fi
-    - uses: actions/checkout@v4.1.1
+        workflow_ref=${{ github.workflow_ref }}
+        repository="${{ github.repository }}/"
+        repo_ref="@${{ github.ref }}"
+        workflow_path=${workflow_ref#"$repository"}
+        workflow_path=${workflow_path%"$repo_ref"}
+
+        ref=$(cat ${workflow_path} | grep assemble_multiarch_image | cut -d"@" -f2)
+        echo "ref=${ref}" >> ${GITHUB_OUTPUT}
+
+    - name: Checkout workflows
+      uses: actions/checkout@v4
       with:
-        repository: ${{ env.WORKFLOW_REPO || github.repository }}
-        ref: ${{ env.WORKFLOW_REF }}
+        repository: canonical/k8s-workflows
+        ref: ${{ steps.workflows-ref.outputs.ref }}
+        path: workflows 
+        token: ${{ secrets.GITHUB_TOKEN }}
+
     - id: assemble-image-tags-js
       uses: juliangruber/read-file-action@v1
       with:
-        path: .github/files/assemble-image-tags.js
+        path: workflows/.github/files/assemble-image-tags.js
         trim: true
+
     - name: Assemble Image Tags
       id: assemble-image-tags
       uses: actions/github-script@v7.0.1
@@ -46,17 +60,20 @@ jobs:
           const rockMetas = JSON.parse(`${{ inputs.rock-metas }}`)
           ${{ steps.assemble-image-tags-js.outputs.content }}
           await main(rockMetas)
+
     - name: Login to Container Registry
       uses: docker/login-action@v3.0.0
       with:
         registry: ${{ inputs.registry }}
         username: ${{ github.actor }}
         password: ${{ secrets.GITHUB_TOKEN }}
+
     - id: create-and-push-manifest-js
       uses: juliangruber/read-file-action@v1
       with:
-        path: .github/files/create-and-push-manifest.js
+        path: workflows/.github/files/create-and-push-manifest.js
         trim: true
+
     - name: Create and Push Manifests
       id: create-and-push-manifest
       uses: actions/github-script@v7.0.1