Restrict the CLI to only root directories, passing the blake3 digest of
the root directory.
Usually we want to serve a directory, and we now have a `snix-castore
ingest` sucommand, and copying the output from that command is much less
effort than constructing a proto message.
More advanced usecases can still use the get_root_node_contents library
function and pass in other nodes.
Change-Id: I66c2c0a15723b43b5b0cffc1c201391df57dd602
Reviewed-on: https://cl.snix.dev/c/snix/+/30321
Reviewed-by: Stefan Junker <mail@stefanjunker.de>
Tested-by: besadii
d1990c9a93