[skip ci] add shell license helper

Author: jdaugherty

etc/bin/add-license-shell.groovy

@@ -0,0 +1,60 @@
+#!/usr/bin/env groovy
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you 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
+ *
+ *    https://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.
+ */
+import java.nio.file.*
+
+def ASF_MARKER = "Licensed to the Apache Software Foundation (ASF) under one"
+def HEADER = '''#
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you 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
+#
+#    https://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.
+#
+'''
+
+String targetPath = args && args[0] ? args[0] : '.'
+def root = Paths.get(targetPath).toRealPath()
+
+Files.walk(root)
+        .filter { path -> Files.isRegularFile(path) && path.toString().endsWith(".sh") }
+        .each { path ->
+            def text = path.toFile().getText("UTF-8")
+            if (!text.contains(ASF_MARKER)) {
+                println "📄 Adding ASF header to ${path}"
+                // Prepend header + existing content
+                path.toFile().withWriter("UTF-8") { writer ->
+                    writer << HEADER
+                    writer << text
+                }
+            }
+        }
+
+println "✅ Done."