If nvm is deactivated, display "none" or "system" instead of the system node version

nvm.sh

@@ -160,7 +160,15 @@ nvm_binary_available() {
 }
 
 nvm_ls_current() {
+  local NODE_PATH
+  NODE_PATH="$(which node)"
+  if [ $? -ne 0 ]; then
+    echo 'none'
+  elif nvm_tree_contains_path "$NVM_DIR" "$NODE_PATH"; then
     echo `node -v 2>/dev/null`
+  else
+    echo 'system'
+  fi
 }
 
 nvm_ls() {

test/fast/Running "nvm current" should display current nvm environment.

@@ -3,4 +3,8 @@
 die () { echo $@ ; exit 1; }
 
 . ../../nvm.sh
-[ "$(nvm current)" = "$(node -v)" ] || die "Failed to find current version"
+
+nvm deactivate 2>&1
+
+[ "$(nvm current)" = "system" ] || [ "$(nvm current)" = "none" ] || die '"nvm current" did not report "system" or "none" when deactivated'
+