$_
nvm.sh
nvm.sh uses `NVM_SCRIPT_SOURCE="$_"` to detect its source location. Adding `: nvm.sh` before each source line ensures `$_` is set correctly, preventing breakage when the previous command (e.g., `set -ex`) overwrites it.
nvm install -s
- add `nvm_use_if_needed` - add `nvm_install_npm_if_needed`