add safeguard to prevent moss from eating your current operating system

[cameronbraid]

Only provide a default value for "root" global argument if the current system is identified as a serpent os.

Currently uses the MACHTYPE env for detection

Manually tested on a arch system :

> moss list installed
Error: args: Root directory is required, but not provided

And when we fake then env we get an expected error

> MACHTYPE=serpent moss list installed
Error: list: client: db: diesel connection: Unable to open the database file

[CLAassistant]

All committers have signed the CLA.

[Quackdoc]

Would it not be better to check /usr/lib/os-release ? I know MACHTYPE can sometimes change depending on shell.

also this seems like it would limit moss to working on serpent as the system package manager. perhaps there could be a better way of doing this. Could this be set via config or something?

[cameronbraid]

What about changing the default back to / and add an assertion that "$root/.moss" folder is present

[cameronbraid]

Although, this might suggest that a separate moss init command should be added as the only means to create a .moss installation... then all other commands could fail if the directory its not a valid installation

[ermo]

The idea of having a well thought out moss init feature that checks for the relevant preconditions etc. sounds compelling.

This migh also tie nicely into potentially setting up the proper minimum SELinux policy for /.moss and /usr in the future.