oh-my-zsh/plugins/bundler/bundler.plugin.zsh

alias be="bundle exec"
alias bl="bundle list"
alias bp="bundle package"
alias bo="bundle open"
alias bu="bundle update"
alias bi="bundle_install"

bundled_commands=(
  annotate
  cap
  capify
  cucumber
  foodcritic
  guard
  irb
  jekyll
  kitchen
  knife
  middleman
  nanoc
  pry
  puma
  rackup
  rainbows
  rake
  rspec
  shotgun
  sidekiq
  spec
  spork
  spring
  strainer
  tailor
  taps
  thin
  thor
  unicorn
  unicorn_rails
)

# Remove $UNBUNDLED_COMMANDS from the bundled_commands list
for cmd in $UNBUNDLED_COMMANDS; do
  bundled_commands=(${bundled_commands#$cmd});
done

# Add $BUNDLED_COMMANDS to the bundled_commands list
for cmd in $BUNDLED_COMMANDS; do
  bundled_commands+=($cmd);
done

## Functions

bundle_install() {
  if _bundler-installed && _within-bundled-project; then
    local bundler_version=`bundle version | cut -d' ' -f3`
    if [[ $bundler_version > '1.4.0' || $bundler_version = '1.4.0' ]]; then
      if [[ "$OSTYPE" = darwin* ]]
      then
        local cores_num="$(sysctl hw.ncpu | awk '{print $2}')"
      else
        local cores_num="$(nproc)"
      fi
      bundle install --jobs=$cores_num $@
    else
      bundle install $@
    fi
  else
    echo "Can't 'bundle install' outside a bundled project"
  fi
}

_bundler-installed() {
  which bundle > /dev/null 2>&1
}

_within-bundled-project() {
  local check_dir="$PWD"
  while [ "$check_dir" != "/" ]; do
    [ -f "$check_dir/Gemfile" ] && return
    check_dir="$(dirname $check_dir)"
  done
  false
}

_binstubbed() {
  [ -f "./bin/${1}" ]
}

_run-with-bundler() {
  if _bundler-installed && _within-bundled-project; then
    if _binstubbed $1; then
      ./bin/$@
    else
      bundle exec $@
    fi
  else
    $@
  fi
}

## Main program
for cmd in $bundled_commands; do
  eval "function unbundled_$cmd () { $cmd \$@ }"
  eval "function bundled_$cmd () { _run-with-bundler $cmd \$@}"
  alias $cmd=bundled_$cmd

  if which _$cmd > /dev/null 2>&1; then
    compdef _$cmd bundled_$cmd=$cmd
  fi
done