read the running rev and the hyperhive flake from /etc files, not the unit

swarm-builder/src/nix_build.rs

@@ -18,6 +18,7 @@ use std::path::PathBuf;
 use std::process::Stdio;
 use std::time::Duration;
 
+use crate::hyperhive_flake::HyperhiveFlake;
 use hive_types::NixBuilds;
 use swarm_wire::builder::{
     BuildAgent, BuildFromMeta, FromMetaReply, LockMeta, LockReply, META_REPO_PATH, Reply,
@@ -46,8 +47,8 @@ pub struct Builder {
     pub nix: PathBuf,
     /// The check flake's directory in the store.
     pub check_flake: String,
-    /// The hyperhive source this host was deployed from.
-    pub hyperhive: String,
+    /// The hyperhive source this host was deployed from, read for each build.
+    pub hyperhive: HyperhiveFlake,
     /// The nixpkgs source this host was deployed from.
     pub nixpkgs: String,
     /// `https://<forge>`, with no trailing slash and no path.
@@ -159,7 +160,7 @@ impl Builder {
             format!("{}#check", self.check_flake),
             "--override-input".to_owned(),
             "hyperhive".to_owned(),
-            self.hyperhive.clone(),
+            self.hyperhive.current(),
             "--override-input".to_owned(),
             "nixpkgs".to_owned(),
             self.nixpkgs.clone(),
@@ -525,7 +526,7 @@ mod tests {
     fn builder() -> Builder {
         Builder {
             check_flake: "/nix/store/c-check".to_owned(),
-            hyperhive: "/nix/store/h-source".to_owned(),
+            hyperhive: HyperhiveFlake::fixed("/nix/store/h-source"),
             nixpkgs: "/nix/store/n-source".to_owned(),
             forge_url: "https://forge.example".to_owned(),
             config_org: "agent-configs".to_owned(),