Add test to check if bazel subdirectory was modified

tools/jenkins/run_bazel_full.sh

@@ -20,4 +20,6 @@ set -ex -o igncr || set -ex
 
 export DOCKERFILE_DIR=tools/dockerfile/test/bazel
 export DOCKER_RUN_SCRIPT=tools/jenkins/run_bazel_full_in_docker.sh
+# Warn PR author if they make a change to the bazel directory
+tools/run_tests/python_utils/check_bazel_dir.py
 exec tools/run_tests/dockerize/build_and_run_docker.sh

tools/run_tests/python_utils/check_bazel_dir.py

+#!/usr/bin/env python
+# Copyright 2017 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.
+
+"""This sends out a warning if any changes to the bazel dir are made."""
+
+from __future__ import print_function
+from subprocess import check_output
+
+import comment_on_pr
+import os
+
+_WARNING_MESSAGE = 'WARNING: You are making changes in the Bazel subdirectory. ' \
+                   'Please get explicit approval from @nicolasnoble before merging.'
+
+
+def _get_changed_files(base_branch):
+  """
+  Get list of changed files between current branch and base of target merge branch
+  """
+  # Get file changes between branch and merge-base of specified branch
+  base_commit = check_output(["git", "merge-base", base_branch, "HEAD"]).rstrip()
+  return check_output(["git", "diff", base_commit, "--name-only"]).splitlines()
+
+
+# ghprbTargetBranch environment variable only available during a Jenkins PR tests
+if 'ghprbTargetBranch' in os.environ:
+  changed_files = _get_changed_files('origin/%s' % os.environ['ghprbTargetBranch'])
+  if any(file.startswith('bazel/') for file in changed_files):
+    comment_on_pr.comment_on_pr(_WARNING_MESSAGE)