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
  fontello
  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