[CI] Adds license headers check in GH Actions

Author: picandocodigo

.github/check-license-headers.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+# Check that source code files in this repo have the appropriate license
+# header.
+
+if [ "$TRACE" != "" ]; then
+    export PS4='${BASH_SOURCE}:${LINENO}: ${FUNCNAME[0]:+${FUNCNAME[0]}(): }'
+    set -o xtrace
+fi
+set -o errexit
+set -o pipefail
+
+TOP=$(cd "$(dirname "$0")/.." >/dev/null && pwd)
+LICENSE=$(cat .github/license-header.txt)
+
+function check_license_header {
+    local f
+    f=$1
+    if ! grep -Fxq "$LICENSE" "$f"; then
+        echo "check-license-headers: error: '$f' does not have required license header"
+        return 1
+    else
+        return 0
+    fi
+}
+
+
+cd "$TOP"
+nErrors=0
+for f in $(git ls-files | grep -E '\.rb|Rakefile|\.rake|\.erb|Gemfile'); do
+    if ! check_license_header $f; then
+        nErrors=$((nErrors+1))
+    fi
+done
+
+if [[ $nErrors -eq 0 ]]; then
+    exit 0
+else
+    exit 1
+fi

.github/license-header.txt

@@ -0,0 +1,16 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. 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
+#
+#   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.

.github/workflows/license.yml

@@ -0,0 +1,10 @@
+name: License headers
+on: [pull_request]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Check license headers
+      run: |
+        ./.github/check-license-headers.sh