✨ Automatically use .nvmrc

Add function to automatically install if applicable, and use the version
of Node.js specified by the .nvmrc, when entering directories with one
available.

node/nvm.zsh

@@ -2,3 +2,31 @@
 
 export NVM_COMPLETION=true
 source ~/.zsh-plugins/zsh-nvm/zsh-nvm.plugin.zsh
+
+# Call nvm use automatically whenever a directory containing .nvmrc is entered.
+autoload -U add-zsh-hook
+
+function load-nvmrc()
+{
+  local nvmrc_path
+  nvmrc_path="$(nvm_find_nvmrc)"
+
+  if [[ -n "$nvmrc_path" ]]; then
+    local nvmrc_node_version
+    nvmrc_node_version=$(nvm version "$(cat "${nvmrc_path}")")
+
+    if [[ "$nvmrc_node_version" == "N/A" ]]; then
+      nvm install
+    elif [[ "$nvmrc_node_version" != "$(nvm version)" ]]; then
+      nvm use
+    fi
+
+  elif [[ -n "$(PWD=$OLDPWD nvm_find_nvmrc)" ]] \
+    && [[ "$(nvm version)" != "$(nvm version default)" ]]; then
+    echo "Reverting to nvm default version"
+    nvm use default
+  fi
+}
+
+add-zsh-hook chpwd load-nvmrc
+load-nvmrc