Add revert command

zsh-nvm.plugin.zsh

@@ -46,6 +46,9 @@ _zsh_nvm_load() {
       'upgrade')
         _zsh_nvm_upgrade
         ;;
+      'revert')
+        _zsh_nvm_revert
+        ;;
       *)
         _zsh_nvm_nvm "$@"
         ;;
@@ -79,6 +82,27 @@ _zsh_nvm_upgrade() {
   fi
 }
 
+_zsh_nvm_previous_version() {
+  cat "$ZSH_NVM_DIR/previous_version" 2>/dev/null
+}
+
+_zsh_nvm_revert() {
+  local previous_version="$(_zsh_nvm_previous_version)"
+  if [[ $previous_version ]]; then
+    local installed_version=$(cd "$NVM_DIR" && git describe --tags)
+    if [[ "$installed_version" = "$previous_version" ]]; then
+      echo "Already reverted to $installed_version"
+      return
+    fi
+    echo "Installed version is $installed_version"
+    echo "Reverting to $previous_version..."
+    $(cd "$NVM_DIR" && git checkout "$previous_version")
+    _zsh_nvm_load
+  else
+    echo "No previous version found"
+  fi
+}
+
 # Install nvm if it isn't already installed
 [[ ! -f "$NVM_DIR/nvm.sh" ]] && _zsh_nvm_install