plugin_update_command() {
  if [ "$#" -ne 1 ]; then
    display_error "usage: asdf plugin-update {<name> | --all}"
    exit 1
  fi

  local plugin_name=$1
  if [ "$plugin_name" = "--all" ]; then
    for dir in $(asdf_dir)/plugins/*; do
      echo "Updating $(basename $dir)..."
      (cd "$dir" && git pull)
    done
  else
    local plugin_path=$(get_plugin_path $plugin_name)
    check_if_plugin_exists $plugin_name
    echo "Updating $plugin_name..."
    (cd $plugin_path; git pull)
  fi
}