git-checkout-pr.sh - fetches a Git pull request from the remote and creates a local branch for it

git-checkout-pr.sh

#!/usr/bin/env bash
set -Eeuo pipefail

log() {
  echo -en '\033[1;32m'
  echo -n "$@"
  echo -e '\033[0m'
}

choice() {
  if [[ $# -gt 0 ]]; then
    # Use the first keyword as a serach keyword to minimize the list results
    SEARCH=$1
  else 
    SEARCH=''
  fi

  # gh pr list command always terminates with exit code 0 in a non-interactive
  # environment. As a workaround, we check whether its output is empty
  # to detect if the command was successful or not.
  PR_CHOICES="$(
    gh pr list --json number,title,author --limit 50 --search "is:open sort:updated-desc $SEARCH" |
    jq -r '.[] | "\u001b[1m#\(.number)\u001b[0m \(.title) \u001b[0;32m@\(.author.login)\u001b[0m"'
  )"
  if [[ -z "$PR_CHOICES" ]]; then
    echo 'Failed to list the pull requests.'
    echo 'Please make sure `gh` command is configured properly.'
    exec gh pr list
  fi

  PR_LENGTH="$(echo "$PR_CHOICES" | wc -l)"

  if [[ "$PR_LENGTH" =~ ^[[:space:]]*1[[:space:]]* ]]; then 
    # The gh pr list command found only one result.
    # Removing ANSI color codes from text
    PR_CHOICE=$(echo $PR_CHOICES | sed -e 's/\x1b\[[0-9;]*m//g')
  else 
    PR_CHOICE="$(
      echo -n "$PR_CHOICES" |
      fzf --ansi --prompt='Choose the pull request to check out: '
    )"
  fi

  if [[ "$PR_CHOICE" =~ (^#([0-9]+) ) ]]; then
    PR_ID="${BASH_REMATCH[2]}"
  else
    echo 'Failed to parse the choice:'
    echo
    echo "  $PR_CHOICE"
    echo
    exit 1
  fi
}

case $# in
0)
  choice
  ;;
1)
  if [[ $1 =~ ^[0=9]+$ ]]; then 
    PR_ID="$1"
  else
    choice $1
  fi
  ;;
*)
  echo "Usage: $0 [<pull request ID> or <search keyword>]" 1>&2
  exit 1
  ;;
esac

PR_INFO="$(gh pr view "$PR_ID" --json 'headRepositoryOwner,headRefName,url')"
PR_AUTHOR="$(echo "$PR_INFO" | jq -r '.headRepositoryOwner.login')"
PR_BRANCH="$(echo "$PR_INFO" | jq -r '.headRefName')"
PR_URL="$(echo "$PR_INFO" | jq -r '.url')"
LOCAL_BRANCH="pr-$PR_ID-$PR_AUTHOR-$PR_BRANCH"

PR_ID_HYPERLINK="$(echo -e "\033]8;;$PR_URL\007#$PR_ID\033]8;;\007")"
if git branch --list --format='%(refname:short)' | grep -qF "$LOCAL_BRANCH"; then
  if [[ "$(git branch --show-current)" == "$LOCAL_BRANCH" ]]; then
    echo "You are already on the branch $LOCAL_BRANCH for $PR_ID_HYPERLINK."
  else
    log "You already have the branch $LOCAL_BRANCH for $PR_ID_HYPERLINK; switching to the local branch .."
    git checkout "$LOCAL_BRANCH"
  fi
  exit 1
else
  log "Checking out the pull request $PR_ID_HYPERLINK into $LOCAL_BRANCH .."
  gh pr checkout "$PR_ID" -b "pr-$PR_ID-$PR_AUTHOR-$PR_BRANCH"
fi