Added change_repo_manager.sh

.github/change_repo_manager.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+#
+# Copyright 2020 The gRPC 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 -e
+
+if [ $# -lt 1 ];then
+  echo "Usage: $0 github-id"
+  exit 1
+fi
+
+echo "Change a repo manager to $0"
+
+BASE_PATH=$(dirname $0)
+
+for file in bug_report.md cleanup_request.md feature_request.md question.md
+do
+	sed -i -E "s/assignees: ([a-zA-Z0-9-]+)/assignees: $1/" $BASE_PATH/ISSUE_TEMPLATE/$file
+done
+
+sed -i -E "s/^@([a-zA-Z0-9-]+)/@$1/" $BASE_PATH/pull_request_template.md
+
+echo "Done"