beam_merge_pr.sh

#!/bin/bash

# This is a utility script to merge pull requests into Apache Beam
# repositories. It supports both repositories, source and website.
#
# Usage:
#    merge_pr.sh [repository] [branch] pull_request_number
#
# Where:
#    repository: { beam | beam-site }
#        Default: beam.
#    branch: { master | asf-site | any_other_branch }
#        Default: master or asf-site, depending on the repository.

# ******************************************************************************

# This function gets called to clean up temporary files and
# revert back to the original state.
function clean_up
{
  # Print final status message.
  echo "$1"

  # Optionally, clean up temporary state.
  read -r -p "Do you want to clean up temporary files? [y/N] " response
  if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]] ; then
    git branch -D "finish-pr-${PR_NUM}" >/dev/null 2>/dev/null || true
    rm -fr "${ROOT_DIR}"
  else
    echo "Temporary workspace left at: ${ROOT_DIR}"
  fi

  # Return back to the original directory.
  popd >/dev/null 2>/dev/null
  exit 0
}

TARGET_REMOTE=apache
SOURCE_REMOTE=github

# Argument parsing.
if [[ $# -eq 1 ]] ; then
  # One argument for pull request number; default others.
  REPOSITORY=beam
  TARGET_BRANCH=master
  PR_NUM=$1

elif [[ $# -eq 2 ]] ; then
  # Two arguments; attempt to figure out whether the user specified repository
  # or branch.
  if [[ "$1" = "beam" ]] ; then
    REPOSITORY=$1
    TARGET_BRANCH=master
    PR_NUM=$2
  elif [[ "$1" = "beam-site" ]] ; then
    REPOSITORY=$1
    TARGET_BRANCH=asf-site
    PR_NUM=$2
  else
    REPOSITORY=beam
    TARGET_BRANCH=$1
    PR_NUM=$2
  fi

elif [[ $# -eq 3 ]] ; then
  # All arguments provided.
  REPOSITORY=$1
  TARGET_BRANCH=$2
  PR_NUM=$3

else
  # Unexpected number of flags. Print usage information.
  echo "Usage: merge_pr.sh [repository] [branch] pull_request_number"
  echo ""
  echo "    repository: { beam | beam-site }"
  echo "        Default: beam."
  echo "    branch: { master | asf-site | any_other_branch }"
  echo "        Default: master or asf-site, depending on the repository."
  exit 1
fi

# Echo display what we are about to do.
echo "Attempting to merge pull request #${PR_NUM} to the branch " \
     "\"${TARGET_BRANCH}\" in the repository \"${REPOSITORY}\"."

# Create temporary directory for this work.
pushd . >/dev/null 2>/dev/null
ROOT_DIR=$(mktemp -d)
cd "$ROOT_DIR"

# Clone the repository and configure it.
git clone --single-branch -b "${TARGET_BRANCH}" \
    "https://github.com/apache/${REPOSITORY}.git" \
    || clean_up "ERROR: Failed to clone GitHub repository."
cd "${REPOSITORY}"

git remote add ${TARGET_REMOTE} \
    "https://git-wip-us.apache.org/repos/asf/${REPOSITORY}.git"
git remote rename origin ${SOURCE_REMOTE}
git config --local --add remote.${SOURCE_REMOTE}.fetch \
    "+refs/pull/*/head:refs/remotes/${SOURCE_REMOTE}/pr/*"

# Fetch everything to make sure we have the last state of the branch.
git fetch ${SOURCE_REMOTE} "pull/${PR_NUM}/head" \
    || clean_up "ERROR: Failed to fetch source pull request."
git fetch ${TARGET_REMOTE} "${TARGET_BRANCH}" \
    || clean_up "ERROR: Failed to fetch target branch."

# Checkout the pull request for merging
git checkout -b "finish-pr-${PR_NUM}" "${SOURCE_REMOTE}/pr/${PR_NUM}" \
    || clean_up "ERROR: Failed to checkout pull request number #${PR_NUM}."

# Infinite loop to iterate on the pull request.
while :
do
  # Rebase the pull request on the target branch.
  git rebase -i "${TARGET_REMOTE}/${TARGET_BRANCH}" \
      || clean_up "ERROR: Failed to rebase on top of " \
                  "${TARGET_REMOTE}/${TARGET_BRANCH}."

  # If the rebase included an interactive command (eg., edit) open a shell to
  # complete it
  while [ -d ".git/rebase-merge" -o -d ".git/rebase-apply" ]; do
    echo "Interactive rebase in progress. Starting a shell shell to finish."
    echo "To resume, complete the rebase and run \"exit\"."
    $SHELL -i

    if [ -d ".git/rebase-merge" -o -d ".git/rebase-apply" ]; then
      read -r -p "Rebase still in progress. Do you want to abort the rebase" \
        response
      if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]]; then
        git rebase --abort;
      fi
    fi
  done

  # Open 'gitk' to review the state of this branch.
  gitk

  # Ask the user whether we should proceed.
  read -r -p "Are you happy with how this branch looks? [y/N] " response
  if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]] ; then
    break
  fi
done

# If website repository, offer to regenerate the site.
if [[ "${REPOSITORY}" = "beam-site" ]] ; then
  read -r -p "Do you want to regenerate the website? [y/N] " \
      response
  if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]] ; then
    bundle exec jekyll build \
        || clean_up "ERROR: Building the website failed. Make sure your " \
             "environment is correctly set up for building the website."

    git add --all -- content
    git commit -m "Regenerate website" \
        || clean_up "ERROR: Couldn't commit the website."
  fi
fi

# At this point, we are happy how the pull request branch looks like.
# Merge it on the target branch.
git checkout "${TARGET_REMOTE}/${TARGET_BRANCH}" \
    || clean_up "ERROR: Failed to checkout target branch " \
         "\"${TARGET_REMOTE}/${TARGET_BRANCH}\"."

git merge --no-ff -m $"This closes #${PR_NUM}" "finish-pr-${PR_NUM}" \
    || clean_up "ERROR: Failed to merge local branch " \
         "\"finish-pr-${PR_NUM}\" to the target branch."

# Open 'gitk' to review the state of this branch.
gitk

# Run 'mvn clean verify', as one more final validation.
if [[ "${REPOSITORY}" = "beam" ]] ; then
  read -r -p "Do you want to skip running 'mvn clean verify' locally? [y/N] " \
      response
  if ! [[ $response =~ ^([yY][eE][sS]|[yY])$ ]] ; then
    mvn clean verify \
        || clean_up "ERROR: Maven test failed. Please fix it before pushing."
  fi
fi

# Ask the user whether we should proceed.
echo "CAUTION -- This is the point of no return! CAUTION!"
read -r -p "Do you want to push this branch? [y/N] " response
if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]] ; then
  git push ${TARGET_REMOTE} "HEAD:${TARGET_BRANCH}" \
      || clean_up "ERROR: Failed to push to \"${TARGET_REMOTE}\" remote.\n" \
            "Run \"git push ${TARGET_REMOTE} HEAD:${TARGET_BRANCH}\" to retry."
fi

clean_up "SUCCESS."