refactor(tvix/derivation): make output hashes an Option<Hash> r/5589

This conveys better if an output of a Derivation is fixed-output or not,
and provides a Hash struct that can be used to store the algo and
digest.

In case it's not, this can simply be None. The serde field attributes
have been updated to still accept the same JSON.

We currently still store the hash algo and digest as strings, mostly
because the only thing populating it so far is the example JSONs.
We might want to update this, once actual Nix code populates this.

While updating write.rs, I pushed some of the Vec<String> to [&str]
conversions inline, and made it a Vec<&str>, because it was annoying to
juggle with.

Change-Id: Ia9cd0568fe179ac22a4a636237f22ab4ad92b95b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7746
Tested-by: BuildkiteCI
Reviewed-by: jrhahn <mail.jhahn@gmail.com>
Reviewed-by: tazjin <tazjin@tvl.su>

0 files changed, 0 insertions, 0 deletions