This reverts commit 02c35ea9df.
Reason for revert: this code path is also used for `Input::getRev()`, i.e. flakes VCS revision validation, which, in the case of Git, are using SHA1.
As a result, this cause too much noise due to SHA1 revisions in Flakes.
Change-Id: I8064c1ebc26e4e83b627f0803a7a9ba56cfe1f37
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/
```
(cherry picked from commit 68c81c737571794f7246db53fb4774e94fcf4b7e)