swarm-controller: render, lock and commit internal/meta

A new update_meta node renders internal/meta's flake.nix with
hive-meta-flake, the renderer hive-c0re uses: hyperhive pinned to its
forge main, each custom agent a hive places pinned to its agent-configs
main, all over https, and the swarm-wide values from
SWARM_CONTROLLER_META_FLAKE (set by swarm-controller.nix from
services.hyperhive.swarm.*). The swarm builder locks it, and the
controller commits flake.nix and flake.lock in one commit and gives
every hive's forge account read on the repo. A render equal to the
committed flake.nix sends no lock and commits nothing.

It runs at start, when hyperhive's main moves, before the deploy of a
merged config PR and before the first deploy of a new agent; those
deploys now wait for it. agent_web_port moves into hive-meta-flake so
both callers compute the same port; hive-c0re re-exports it.

On deploy: internal/meta appears on the forge and follows every merge.
No hive builds from it yet.

Refs #4857

swarm-controller/src/forge/meta_repo.rs

@@ -0,0 +1,77 @@
+//! `internal/meta` on the forge: the repo the swarm meta flake is committed to
+//! (`crate::meta_flake`), and the read grant each hive's account holds on it.
+
+use anyhow::{Context, Result};
+use base64::Engine as _;
+use forgejo_api::structs::{
+    AddCollaboratorOptionPermission, ChangeFileOperation, ChangeFileOperationOperation,
+    ChangeFilesOptions,
+};
+
+use super::objects::SHARED_ORG;
+use super::{Client, DefaultBranchFiles};
+use crate::meta_flake::{META_REPO, MetaFile, MetaForge};
+
+impl MetaForge for Client {
+    async fn head_files(
+        &self,
+        owner: &str,
+        repo: &str,
+        paths: &[&str],
+    ) -> Result<Option<DefaultBranchFiles>> {
+        self.default_branch_files(owner, repo, paths).await
+    }
+
+    async fn ensure_meta_repo(&self) -> Result<()> {
+        self.create_shared_repo(SHARED_ORG, META_REPO, true).await
+    }
+
+    async fn grant_meta_read(&self, login: &str) -> Result<()> {
+        self.add_collaborator_to(
+            SHARED_ORG,
+            META_REPO,
+            login,
+            AddCollaboratorOptionPermission::Read,
+        )
+        .await
+    }
+
+    async fn commit_meta(&self, message: &str, files: Vec<MetaFile>) -> Result<()> {
+        let ops: Vec<ChangeFileOperation> = files
+            .into_iter()
+            .map(|f| ChangeFileOperation {
+                content: Some(base64::engine::general_purpose::STANDARD.encode(f.bytes)),
+                from_path: None,
+                operation: if f.sha.is_some() {
+                    ChangeFileOperationOperation::Update
+                } else {
+                    ChangeFileOperationOperation::Create
+                },
+                path: f.path.to_owned(),
+                sha: f.sha,
+            })
+            .collect();
+        self.api
+            .call(|api| {
+                api.repo_change_files(
+                    SHARED_ORG,
+                    META_REPO,
+                    ChangeFilesOptions {
+                        author: None,
+                        branch: None,
+                        committer: None,
+                        dates: None,
+                        files: ops.clone(),
+                        force_overwrite_new_branch: None,
+                        message: Some(message.to_owned()),
+                        new_branch: None,
+                        signoff: None,
+                    },
+                )
+                .into_future()
+            })
+            .await
+            .with_context(|| format!("commit to {SHARED_ORG}/{META_REPO}"))?;
+        Ok(())
+    }
+}