renderdiff: enable update goldens on commit merge (#8771)

test/renderdiff/src/commit_msg.py

@@ -0,0 +1,60 @@
+# Copyright (C) 2025 The Android Open Source Project
+#
+# 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 sys
+import re
+
+from utils import execute, ArgParseImpl
+
+RDIFF_UPDATE_GOLDEN_STR = 'RDIFF_BRANCH'
+
+def _parse_commit(commit_str):
+  commit, author, date, _, title, *desc = commit_str.split('\n')
+  commit = commit.split(' ')[1]
+  title = title.strip()
+
+  desc = [l.strip() for l in desc[1:]]
+  while len(desc) > 0 and len(desc[0]) == 0:
+    desc = desc[1:]
+
+  return (
+    commit,
+    title,
+    desc
+  )
+
+if __name__ == "__main__":
+  RE_STR = rf"{RDIFF_UPDATE_GOLDEN_STR}(?:S)?=[\[]?([a-zA-Z0-9,\s\-\/]+)[\]]?"
+
+  parser = ArgParseImpl()
+  parser.add_argument('--file', help='A file containing the commit message')
+  args, _ = parser.parse_known_args(sys.argv[1:])
+
+  if not args.file:
+    msg = sys.stdin.read()
+  else:
+    with open(args.file, 'r') as f:
+      msg = f.read()
+
+  to_update = []
+  commit, title, description = _parse_commit(msg)
+  for line in description:
+    m = re.match(RE_STR, line)
+    if not m:
+      continue
+    print(m.group(1))
+    exit(0)
+
+  # Always default to the main branch
+  print('main')