guet set runs in non-git folders

[chiptopher]

Bug report

Calling guet set from folder that isn't a git project still succeeds.

Actual behavior?

In /path/to/projectA calling guet set cb will add cb,1579969290283,/path/to/projectA/.git even though no /path/to/projectA/.git folder exists.

Expected behavior?

An error method should appear that says something to the effect of git not initialized in this directory., similar to how it does for running guet start in a non-git initialized directory.