recovering from interrupted setup

[phoddie]

Installing can be interrupted, so xs-dev should recover gracefully to avoid leaving the installation in a bad state. Installs are even somewhat likely to be interrupted because some of them take a while to execute (lots to download, for example).

I experimented with this on macOS by hitting Control-C to interrupt the Moddable SDK and ESP8266 setup. If the Moddable SDK setup is interrupted, it seems to always leave behind a /moddable directory. which is enough to cause later attempt to xs-dev setup to fail to complete a real setup. The ESP8266 seems to recover better, but it does leave a partial installation.

For setup, maybe it is best to remove all the bits of the setup fails for some reason? That won't work for update though. I'm not sure what best practices are here.

The good news is that xs-dev teardown does get back to a safe state so setup can proceed again. But, that's only an option once the developer understands that they have a partial install that needs to be cleaned up before proceeding.