[Refactor] `bash_completion`: Improve coding style

bash_completion

@@ -6,17 +6,15 @@ if ! command -v nvm &> /dev/null; then
   return
 fi
 
-__nvm_generate_completion()
-{
+__nvm_generate_completion() {
   declare current_word
   current_word="${COMP_WORDS[COMP_CWORD]}"
   # shellcheck disable=SC2207
-  COMPREPLY=($(compgen -W "$1" -- "$current_word"))
+  COMPREPLY=($(compgen -W "$1" -- "${current_word}"))
   return 0
 }
 
-__nvm_commands ()
-{
+__nvm_commands() {
   declare current_word
   declare command
 
@@ -41,44 +39,39 @@ __nvm_commands ()
 
     case "${current_word}" in
       -*) __nvm_options ;;
-      *)      __nvm_generate_completion "$COMMANDS" ;;
+      *) __nvm_generate_completion "${COMMANDS}" ;;
     esac
 
   fi
 }
 
-__nvm_options ()
-{
+__nvm_options() {
   OPTIONS=''
-  __nvm_generate_completion "$OPTIONS"
+  __nvm_generate_completion "${OPTIONS}"
 }
 
-__nvm_installed_nodes ()
-{
+__nvm_installed_nodes() {
   __nvm_generate_completion "$(nvm_ls) $(__nvm_aliases)"
 }
 
-__nvm_aliases ()
-{
+__nvm_aliases() {
   declare aliases
   aliases=""
-  if [ -d "$NVM_DIR/alias" ]; then
-    aliases="$(cd "$NVM_DIR/alias" && command find "$PWD" -type f | command sed "s:$PWD/::")"
+  if [ -d "${NVM_DIR}/alias" ]; then
+    aliases="$(cd "${NVM_DIR}/alias" && command find "${PWD}" -type f | command sed "s:${PWD}/::")"
   fi
   echo "${aliases} node stable unstable iojs"
 }
 
-__nvm_alias ()
-{
+__nvm_alias() {
   __nvm_generate_completion "$(__nvm_aliases)"
 }
 
-__nvm ()
-{
+__nvm() {
   declare previous_word
   previous_word="${COMP_WORDS[COMP_CWORD - 1]}"
 
-  case "$previous_word" in
+  case "${previous_word}" in
     use | run | exec | ls | list | uninstall) __nvm_installed_nodes ;;
     alias | unalias) __nvm_alias ;;
     *) __nvm_commands ;;