Restore add-boilerplate script

Author: cardil

hack/add-boilerplate.sh

@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+
+# Copyright 2019 The Knative 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.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+# shellcheck disable=SC1090
+source "$(GOFLAGS='-mod=mod' go run knative.dev/hack/cmd/script codegen-library.sh)"
+
+USAGE=$(cat <<EOF
+Add boilerplate.<ext>.txt to all .<ext> files missing it in a directory.
+
+Usage: (from repository root)
+       ./hack/boilerplate/add-boilerplate.sh <ext> <DIR>
+
+Example: (from repository root)
+         ./hack/boilerplate/add-boilerplate.sh go cmd
+
+As of now, only .go files are supported.
+EOF
+)
+
+if [ -z "${1:-}" ] || [ -z "${2:-}" ]; then
+  error Invalid arguments
+  echo "${USAGE}" 1>&2
+  exit 1
+fi
+
+if ! [[ "$1" = "go" ]]; then
+  error Unsupported file extension
+  echo "${USAGE}" 1>&2
+  exit 2
+fi
+
+cnt=0
+while read -r file; do
+  if grep -q -E "^Copyright [[:digit:]]+ The Knative Authors$" "$file"; then
+    continue
+  fi
+  cat "$(boilerplate)" > "$file".bck
+  echo '' >> "$file".bck
+  cat "$file" >> "$file".bck
+  mv "$file".bck "$file"
+  log License added to "$file"
+  cnt=$(( cnt + 1))
+done < <(find "$2" -type f -name "*.$1")
+
+log License added to $cnt files