Automatic cherry-pick script (#339)

* Automatic cherry-pick script

* switch from alamb to apache

* autopep8

* flake8

* add rat

* tweaks

* Add some docs to the README

dev/release/README.md

@@ -234,3 +234,31 @@ following commands
 (cd parquet && cargo publish)
 (cd parquet_derive && cargo publish)
 ```
+
+# Backporting
+
+As of now, the plan for backporting to `active_release` is to do so semi-manually.
+
+Step 1: Pick the commit to cherry-pick
+
+Step 2: Create cherry-pick PR to active_release
+
+Step 3a: If CI passes, merge cherry-pick PR
+
+Step 3b: If CI doesn't pass or some other changes are needed, the PR should be reviewed / approved as normal prior to merge
+
+
+
+For example, to backport `b2de5446cc1e45a0559fb39039d0545df1ac0d26` to active_release use the folliwing
+
+```shell
+git clone [email protected]:apache/arrow-rs.git /tmp/arrow-rs
+
+ARROW_GITHUB_API_TOKEN=$ARROW_GITHUB_API_TOKEN CHECKOUT_ROOT=/tmp/arrow-rs CHERRY_PICK_SHA=b2de5446cc1e45a0559fb39039d0545df1ac0d26 python3 dev/release/cherry-pick-pr.py
+```
+
+## Rationale for creating PRs:
+1. PRs are a natural place to run the CI tests to make sure there are no logical conflicts
+2. PRs offer a place for the original author / committers to comment and say it should/should not be backported.
+3. PRs offer a way to make cleanups / fixups and approve (if needed) for non cherry pick PRs
+4. There is an additional control / review when the candidate release is created

dev/release/cherry-pick-pr.py

@@ -0,0 +1,147 @@
+#!/usr/bin/python3
+##############################################################################
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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 script is designed to create a cherry pick PR to a target branch
+#
+# Usage: python3 cherry_pick_pr.py
+#
+# To test locally:
+#
+# git clone [email protected]:apache/arrow-rs.git /tmp/arrow-rs
+#
+# pip3 install PyGithub
+# ARROW_GITHUB_API_TOKEN=<..>
+#     CHECKOUT_ROOT=<path>
+#     CHERRY_PICK_SHA=<sha> python3 cherry-pick-pr.py
+#
+import os
+import sys
+import six
+import subprocess
+
+from pathlib import Path
+
+TARGET_BRANCH = 'active_release'
+TARGET_REPO = 'apache/arrow-rs'
+
+p = Path(__file__)
+
+# Use github workspace if specified
+repo_root = os.environ.get("CHECKOUT_ROOT")
+if repo_root is None:
+    print("arrow-rs checkout must be supplied in CHECKOUT_ROOT environment")
+    sys.exit(1)
+
+print("Using checkout in {}".format(repo_root))
+
+token = os.environ.get('ARROW_GITHUB_API_TOKEN', None)
+if token is None:
+    print("GITHUB token must be supplied in ARROW_GITHUB_API_TOKEN environmet")
+    sys.exit(1)
+
+new_sha = os.environ.get('CHERRY_PICK_SHA', None)
+if new_sha is None:
+    print("SHA to cherry pick must be supplied in CHERRY_PICK_SHA environment")
+    sys.exit(1)
+
+
+# from merge_pr.py from arrow repo
+def run_cmd(cmd):
+    if isinstance(cmd, six.string_types):
+        cmd = cmd.split(' ')
+    try:
+        output = subprocess.check_output(cmd)
+    except subprocess.CalledProcessError as e:
+        # this avoids hiding the stdout / stderr of failed processes
+        print('Command failed: %s' % cmd)
+        print('With output:')
+        print('--------------')
+        print(e.output)
+        print('--------------')
+        raise e
+
+    if isinstance(output, six.binary_type):
+        output = output.decode('utf-8')
+
+    return output
+
+
+os.chdir(repo_root)
+new_sha_short = run_cmd("git rev-parse --short {}".format(new_sha)).strip()
+new_branch = 'cherry_pick_{}'.format(new_sha_short)
+
+
+def make_cherry_pick():
+    if os.environ.get('GITHUB_SHA', None) is not None:
+        print("Running on github runner, setting email/username")
+        run_cmd(['git', 'config', 'user.email', '[email protected]'])
+        run_cmd(['git', 'config', 'user.name', 'Arrow-RS Automation'])
+
+    #
+    # Create a new branch from active_release
+    # and cherry pick to there.
+    #
+
+    print("Creating cherry pick from {} to {}".format(
+        new_sha_short, new_branch
+    ))
+
+    # The following tortured dance is required due to how the github
+    # actions/checkout works (it doesn't pull other branches and pulls
+    # only one commit back)
+
+    # pull 10 commits back so we can get the proper cherry pick
+    # (probably only need 2 but 10 must be better, right?)
+    run_cmd(['git', 'fetch', '--depth', '10', 'origin', 'master'])
+    run_cmd(['git', 'fetch', 'origin', 'active_release'])
+    run_cmd(['git', 'checkout', '-b', new_branch])
+    run_cmd(['git', 'reset', '--hard', 'origin/active_release'])
+    run_cmd(['git', 'cherry-pick', new_sha])
+    run_cmd(['git', 'push', '-u', 'origin', new_branch])
+
+
+def make_cherry_pick_pr():
+    from github import Github
+    g = Github(token)
+    repo = g.get_repo(TARGET_REPO)
+
+    # Default titles
+    new_title = 'Cherry pick {} to active_release'.format(new_sha)
+    new_commit_message = 'Automatic cherry-pick of {}\n'.format(new_sha)
+
+    # try and get info from github api
+    commit = repo.get_commit(new_sha)
+    for orig_pull in commit.get_pulls():
+        new_commit_message += '* Originally appeared in {}: {}\n'.format(
+            orig_pull.html_url, orig_pull.title)
+        new_title = 'Cherry pick {} to active_release'.format(orig_pull.title)
+
+    pr = repo.create_pull(title=new_title,
+                          body=new_commit_message,
+                          base='refs/heads/active_release',
+                          head='refs/heads/{}'.format(new_branch),
+                          maintainer_can_modify=True
+                          )
+
+    print('Created PR {}'.format(pr.html_url))
+
+
+make_cherry_pick()
+make_cherry_pick_pr()