booststrap/apply scripts are failing if they sylva-core is not a git repository.

Summary

In a downstream deployment of sylva based on OCI artificats, we only need a subset of sylva-core project content. In that case it may not be a valid git repository.

In that case ensure_source function will fail to determine SYLVA_CORE_COMMIT and exit here without passing the input manifests through.

The deployment will fail with following error:

📜 Update sylva-units Helm release and associated resources
[INFO] Unable to determine current commit. Make sure to use OCI artifacts for deployment
error: no objects passed to apply

Whereas it is not relevant to determine SYLVA_CORE_COMMIT