Purpose for this repo?

I only see one potential use case for this repo, but it doesn't seem to be used for it. Therefore I wonder if there are other use cases for this repo?

### The one (unused) use case I know about

From clues gleaned from the [curator README](https://github.com/commercialhaskell/curator/blob/master/README.md#basic-workflow), it sounds like the curator workflow was designed such that curators could "edit `constraints.yaml` to make tweaks to the build plan".

*If* curators did modify constraints.yaml, it would make sense to record the final product, which is what I suppose this repo is for.

However, currently curation is automated, and there is [no manual gap](https://github.com/commercialhaskell/stackage/blob/master/automated/build.sh#L120) between generating constraints.yaml and moving immediately to generating snapshot.yaml (via snapshot-incomplete.yaml):

```bash
docker run $ARGS_PREBUILD $IMAGE /bin/bash -c \
"curator constraints --target $TARGET && \
curator snapshot-incomplete --target $TARGET && \
curator snapshot"
```

Thus I wonder if we still need to write constraints.yaml to this repo. Does anybody else use it for anything? Do curators do anything interesting with constraints.yaml manually?