Right, for almost all uses of ec-backup we need to use the defaults since we explicitly look at the _path variables inside chef_fs.  Hence the commit message:

```
It seems that setting the various _path variables to nil prevents
them from being generated automatically from chef_repo_path.

We depend on their automatic generation.
```

I think though that your suggestion of the new Chef::Config.save and .restore will actually do everything we need for now.  I'm close to having a version that doesn't require global config mutation, so we won't have to live with this for too long.