Relnotes python script

scripts/release/relnotes.py

@@ -0,0 +1,101 @@
+# Copyright 2022 The Bazel 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 re
+import requests
+import subprocess
+
+
+def get_last_release():
+  """Discovers the last stable release name from GitHub."""
+  response = requests.get('https://github.com/bazelbuild/bazel/releases/latest')
+  return response.url.split("/")[-1]
+
+
+def git(*args):
+  """Runs git as a subprocess, and returns its stdout as a list of lines."""
+  return subprocess.check_output(["git"] + list(args)).decode(
+    "utf-8").strip().split("\n")
+
+
+def extract_relnotes(commit_message_lines):
+  """Extracts relnotes from a commit message (passed in as a list of lines)."""
+  relnote_lines = []
+  in_relnote = False
+  for line in commit_message_lines:
+    if line == "" or line.startswith("PiperOrigin-RevId:"):
+      in_relnote = False
+    m = re.match(r"^RELNOTES(?:\[(INC|NEW)\])?:", line)
+    if m is not None:
+      in_relnote = True
+      line = line[len(m[0]):]
+      if m[1] == "INC":
+        line = "**[Incompatible]** " + line.strip()
+    line = line.strip()
+    if in_relnote and line != "":
+      relnote_lines.append(line)
+  relnote = " ".join(relnote_lines)
+  relnote_lower = relnote.strip().lower().rstrip(".")
+  if relnote_lower == "n/a" or relnote_lower == "none":
+    return None
+  return relnote
+
+
+def get_relnotes_between(base, head):
+  """Gets all relnotes for commits between `base` and `head`."""
+  commits = git("rev-list", f"{base}..{head}", "--grep=RELNOTES")
+  relnotes = []
+  rolled_back_commits = set()
+  # We go in reverse-chronological order, so that we can identify rollback
+  # commits and ignore the rolled-back commits.
+  for commit in commits:
+    if commit in rolled_back_commits:
+      continue
+    lines = git("show", "-s", commit, "--pretty=format:%B")
+    m = re.match(r"^Automated rollback of commit ([\dA-Fa-f]+)", lines[0])
+    if m is not None:
+      rolled_back_commits.add(m[1])
+      # The rollback commit itself is also skipped.
+      continue
+    relnote = extract_relnotes(lines)
+    if relnote is not None:
+      relnotes.append(relnote)
+  return relnotes
+
+
+if __name__ == "__main__":
+  # Get the last stable release.
+  last_release = get_last_release()
+  print("last_release is", last_release)
+  git("fetch", "origin", f"refs/tags/{last_release}:refs/tags/{last_release}")
+
+  # Assuming HEAD is on the current (to-be-released) release, find the merge
+  # base with the last release so that we know which commits to generate notes
+  # for.
+  merge_base = git("merge-base", "HEAD", last_release)[0]
+  print("merge base with", last_release, "is", merge_base)
+
+  # Generate notes for all commits from last branch cut to HEAD, but filter out
+  # any identical notes from the previous release branch.
+  cur_release_relnotes = get_relnotes_between(merge_base, "HEAD")
+  last_release_relnotes = set(get_relnotes_between(merge_base, last_release))
+  filtered_relnotes = [note for note in cur_release_relnotes
+                       if note not in last_release_relnotes]
+
+  # Reverse so that the notes are in chronological order.
+  filtered_relnotes.reverse()
+  print()
+  print()
+  for note in filtered_relnotes:
+    print("*", note)