universal installer behavior

[dherman]

What things should all installers do universally?

• Create the appropriate directories
• Find existing Node installs and gracefully supersede them with shims
• Find existing global Node packages and gracefully supersede them with shims

What are the differences across OSes?

• On Windows, Notion needs to be installed as a shared install instead of a per-user install because of the backwards precedence of Windows environment variables (system variables supersede user variables).
• In Unix, Notion needs to be installed as a user install because many users don't have administrative privileges.