Custom backport script for grpc repos

backport.sh

#!/usr/bin/env bash
# Copyright 2020 The 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.

set -e

display_usage() {
  cat <<EOF >/dev/stderr
Usage: $0 REPO PR MINOR_VERSIONS

EXAMPLES:
$0 grpc-go 5434 47 46 45
$0 grpc 5434 47
$0 grpc-java 5434 {47..38}
$0 grpc-node 2208 5 6 7
EOF
  exit 1
}

urlencode() {
  python3 -c "import urllib.parse, sys; print(urllib.parse.quote(sys.argv[1]))" "$*"
}

main() {
  if (( $# < 3 )); then
    display_usage
  fi

  readonly repo="$1"
  readonly pr="$2"
  readonly labels="${LABELS:-}"
  shift 2
  readonly minors="$@"
  readonly owner="$(git remote get-url origin | sed -E "s#.*[:/]([a-zA-Z0-9-]+)/${repo}.*#\1#")"

  readonly pr_metadata="$(curl -sSf -H "Accept: application/vnd.github.v3+json" "https://api.github.com/repos/grpc/${repo}/pulls/$pr")"
  readonly assignee="$(echo "$pr_metadata" | jq -r '.assignee.login')"
  readonly commits="$(echo "$pr_metadata" | jq -r '.merge_commit_sha')"
  readonly branch_id="$(echo "$pr_metadata" | jq -r '.head.ref')"
  readonly title="$(echo "$pr_metadata" | jq -r '.title')"
  readonly body="$(echo "$pr_metadata" | jq -r '.body')"

  cat <<EOT
PR: https://github.com/grpc/${repo}/pull/$pr
Versions: ${minors}
Commits: ${commits}
Branch id: ${branch_id}
Repo: ${owner}
Assignee: ${assignee}
Labels: ${labels}
EOT

  read -n 1 -p "Continue? (y/N) " answer
  if [ "$answer" != "${answer#[Yy]}" ] ;then
    echo
  else
    echo
    echo "Exit"
    exit 1
  fi

  git fetch upstream
  readonly orig_branch="$(git rev-parse --abbrev-ref HEAD)"
  local pick_result
  local backport_branch
  local arg_title
  local arg_body
  local version_tag
  local url

  for minor in $minors; do
    backport_branch="backport-1.$minor-${branch_id}"
    if [[ "${repo}" == "grpc-node" ]]; then
      version_tag="@grpc/grpc-js@1.${minor}.x"
    else
      version_tag="v1.${minor}.x"
    fi
    git checkout -b "${backport_branch}" "upstream/${version_tag}"
    pick_result=0
    git cherry-pick --rerere-autoupdate -m 1 $commits || pick_result=$?
    if [[ $pick_result -ne 0 ]]; then
      read -n 1 -p "Conflict detected. Resolve manually in another shell. Resolved? (y/N) " answer
      if [ "$answer" != "${answer#[Yy]}" ] ;then
        echo
        echo "Continuing..."
      else
        echo
        echo "Aborting. Cleaning up..."
        git checkout -f "${orig_branch}"
        git branch -D "${backport_branch}"
        exit 1
      fi
    fi
    git push --set-upstream origin "${backport_branch}"

    arg_title="${title} (${version_tag} backport)"
    arg_body=$(cat <<EOT
Backport of #${pr} to ${version_tag}.
---
${body}
EOT
)
    # https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/using-query-parameters-to-create-a-pull-request
    url="https://github.com/grpc/${repo}/compare"
    url="${url}/$(urlencode "${version_tag}")...${owner}:${backport_branch}?quick_pull=1"
    url="${url}&title=$(urlencode "${arg_title}")"
    url="${url}&body=$(urlencode "${arg_body}")"
    if [[ "${assignee}" != "null" ]]; then
      url="${url}&assignees=${assignee}"
    fi
    if [[ -n "${labels}" ]]; then
      url="${url}&labels=$(urlencode "${labels}")"
    fi

    echo
    echo
    echo ------------------------------------------------------
    echo "${url}"
    echo ------------------------------------------------------
    echo
    echo
  done
  git checkout "${orig_branch}"
}

main "$@"