I think it is bad for these reasons when `tests/` contains a mix of
functional and integration tests
- Concepts is harder to understand, the documentation makes a good
unit vs functional vs integration distinction, but when the
integration tests are just two subdirs within `tests/` this is not
clear.
- Source filtering in the `flake.nix` is more complex. We need to
filter out some of the dirs from `tests/`, rather than simply pick
the dirs we want and take all of them. This is a good sign the
structure of what we are trying to do is not matching the structure
of the files.
With this change we have a clean:
```shell-session
$ git show 'HEAD:tests'
tree HEAD:tests
functional/
installer/
nixos/
```
This is requires if you have attribute names with dots in them. So
you can now say:
$ nix-instantiate '<nixos>' -A 'config.systemd.units."postgresql.service".text' --eval-only
Fixes#151.
sure that it works as expected when you pass it a derivation. That
is, we have to make sure that all build-time dependencies are built,
and that they are all in the input closure (otherwise remote builds
might fail, for example). This is ensured at instantiation time by
adding all derivations and their sources to inputDrvs and inputSrcs.
