feat: add reusable verify-boilerplate composite action

.github/actions/verify-boilerplate/action.yml

@@ -0,0 +1,74 @@
+# Copyright The Kubeflow Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Verify Boilerplate Headers
+description: >
+  Verify that every source file carries the required Apache 2.0 copyright
+  header. Wraps hack/boilerplate/boilerplate.py from kubeflow/testing so
+  callers never need to vendor the script.
+
+inputs:
+  base-ref:
+    description: >
+      Base branch for new-file detection. Defaults to the pull-request base
+      branch (github.base_ref) so only changed/new files are flagged for
+      year-less header enforcement.
+    required: false
+    default: ""
+  boilerplate-dir:
+    description: >
+      Directory containing boilerplate template files (boilerplate.*.txt).
+      Leave empty to use the templates shipped with kubeflow/testing.
+    required: false
+    default: ""
+  python-version:
+    description: Python version to use.
+    required: false
+    default: "3.12"
+
+runs:
+  using: composite
+  steps:
+    - name: Set up Python
+      uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+      with:
+        python-version: ${{ inputs.python-version }}
+
+    - name: Checkout kubeflow/testing
+      uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      with:
+        repository: kubeflow/testing
+        path: .kubeflow-testing
+        sparse-checkout: hack/boilerplate
+
+    - name: Run boilerplate check
+      shell: bash
+      env:
+        BASE_REF: ${{ inputs.base-ref || github.base_ref || 'master' }}
+        BOILERPLATE_DIR: ${{ inputs.boilerplate-dir }}
+      run: |
+        ARGS=("--base-ref" "${BASE_REF}")
+
+        if [[ -n "${BOILERPLATE_DIR}" ]]; then
+          ARGS+=("--boilerplate-dir" "${BOILERPLATE_DIR}")
+        else
+          ARGS+=("--boilerplate-dir" ".kubeflow-testing/hack/boilerplate")
+        fi
+
+        python .kubeflow-testing/hack/boilerplate/boilerplate.py "${ARGS[@]}"
+
+    - name: Cleanup
+      if: always()
+      shell: bash
+      run: rm -rf .kubeflow-testing