Allow passing in an extra TUF manifest (#6595)

It's sometimes useful to be able to add extra artifacts to a TUF repo,
especially when testing hubris related changes. Add an option to releng
to take an extra manifest to be merged in.

dev-tools/releng/src/main.rs

@@ -147,6 +147,10 @@ struct Args {
     /// Build the helios OS image from local sources.
     #[clap(long)]
     helios_local: bool,
+
+    /// Extra manifest to be merged with the rest of the repo
+    #[clap(long)]
+    extra_manifest: Option<Utf8PathBuf>,
 }
 
 impl Args {
@@ -592,6 +596,7 @@ async fn main() -> Result<()> {
             args.output_dir.clone(),
             version,
             manifest,
+            args.extra_manifest,
         ),
     )
     .after("tuf-stamp")

dev-tools/releng/src/tuf.rs

@@ -33,6 +33,7 @@ pub(crate) async fn build_tuf_repo(
     output_dir: Utf8PathBuf,
     version: Version,
     package_manifest: Arc<Config>,
+    extra_manifest: Option<Utf8PathBuf>,
 ) -> Result<()> {
     // We currently go about this somewhat strangely; the old release
     // engineering process produced a Tufaceous manifest, and (the now very many
@@ -58,6 +59,14 @@ pub(crate) async fn build_tuf_repo(
         manifest.artifacts.entry(kind).or_default().extend(artifacts);
     }
 
+    if let Some(path) = extra_manifest {
+        let m = DeserializedManifest::from_path(&path)
+            .context("failed to open extra manifest")?;
+        for (kind, artifacts) in m.artifacts {
+            manifest.artifacts.entry(kind).or_default().extend(artifacts);
+        }
+    }
+
     // Add the OS images.
     manifest.artifacts.insert(
         KnownArtifactKind::Host,