chore: import upstream snapshot with attribution

tools/diff_api.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# 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.
+
+import difflib
+import sys
+
+with open(sys.argv[1], 'r') as f:
+    origin = f.read()
+    origin = origin.splitlines()
+
+with open(sys.argv[2], 'r') as f:
+    new = f.read()
+    new = new.splitlines()
+
+differ = difflib.Differ()
+result = differ.compare(origin, new)
+
+error = False
+diffs = []
+for each_diff in result:
+    if each_diff[0] in ['-', '?']:  # delete or change API is not allowed
+        error = True
+    elif each_diff[0] == '+':
+        error = True
+
+    if each_diff[0] != ' ':
+        diffs.append(each_diff)
+'''
+If you modify/add/delete the API files, including code and comment,
+please follow these steps in order to pass the CI:
+
+  1. cd ${paddle_path}, compile paddle;
+  2. pip install build/python/dist/(build whl package);
+  3. run "python tools/print_signatures.py paddle.base> paddle/fluid/API.spec"
+'''
+if error:
+    print('API Difference is: ')
+    for each_diff in diffs:
+        print(each_diff)