fix(#1060): dynamic meta commit message from staged files; skip commit on no-op

hive-c0re/src/meta.rs

@@ -90,7 +90,7 @@ pub async fn sync_agents(
     // only fills in missing entries. Idempotent; when nothing changed
     // the file isn't touched.
     let agent_names: Vec<String> = agents.iter().map(|a| a.name.clone()).collect();
-    let topology_changed = crate::topology::reconcile(&agent_names)
+    crate::topology::reconcile(&agent_names)
         .with_context(|| format!("reconcile {}", crate::topology::topology_path().display()))?;
 
     // Refresh /var/lib/hyperhive/agent-ports.json so the hive-gateway
@@ -168,12 +168,35 @@ pub async fn sync_agents(
     if std::path::Path::new(&dir).join("flake.lock").exists() {
         git(&dir, &["add", "flake.lock"]).await?;
     }
+    // Build the commit message from what's actually staged so it
+    // reflects reality — and skip the commit entirely when nothing
+    // changed (avoids "nothing to commit" errors on redundant syncs).
+    let staged = git_staged_names(&dir).await?;
+    if staged.is_empty() {
+        return Ok(());
+    }
     let msg = if initial {
         format!("seed meta from {} agent(s)", agents.len())
-    } else if topology_changed {
-        "regenerate meta flake + topology".to_owned()
     } else {
-        "regenerate meta flake".to_owned()
+        // Compose a message that names every file that actually changed,
+        // mapping the on-disk filename to a short human label.
+        let labels: Vec<&str> = staged
+            .iter()
+            .filter_map(|f| match f.as_str() {
+                "flake.nix" => Some("flake"),
+                "flake.lock" => Some("lock"),
+                "topology.json" => Some("topology"),
+                "capabilities.json" => Some("capabilities"),
+                "tool-groups.json" => Some("tool-groups"),
+                "roles.json" => Some("roles"),
+                _ => None,
+            })
+            .collect();
+        if labels.is_empty() {
+            "meta: update".to_owned()
+        } else {
+            format!("meta: update {}", labels.join(", "))
+        }
     };
     git_commit(&dir, &msg).await?;
     Ok(())
@@ -625,6 +648,44 @@ async fn git_is_clean(dir: &Path) -> Result<bool> {
     Ok(out.stdout.iter().all(u8::is_ascii_whitespace))
 }
 
+/// Return the list of file names that are currently staged (index differs
+/// from HEAD). On the initial commit (`HEAD` doesn't exist yet) falls back
+/// to `git diff --cached --name-only HEAD` failing gracefully by using
+/// `git status --porcelain` and collecting the `A ` / `M ` prefix lines.
+async fn git_staged_names(dir: &Path) -> Result<Vec<String>> {
+    // `--diff-filter=ACM` skips deleted entries — we only care about
+    // additions and modifications for message-building purposes.
+    let out = lifecycle::git_command()
+        .current_dir(dir)
+        .args(["diff", "--cached", "--name-only", "--diff-filter=ACM"])
+        .output()
+        .await
+        .with_context(|| format!("git diff --cached in {}", dir.display()))?;
+    if out.status.success() {
+        let names = String::from_utf8_lossy(&out.stdout)
+            .lines()
+            .map(str::trim)
+            .filter(|l| !l.is_empty())
+            .map(ToOwned::to_owned)
+            .collect();
+        return Ok(names);
+    }
+    // Fallback for initial commit (no HEAD yet): parse `git status --porcelain`.
+    let st = lifecycle::git_command()
+        .current_dir(dir)
+        .args(["status", "--porcelain"])
+        .output()
+        .await
+        .with_context(|| format!("git status in {}", dir.display()))?;
+    let names = String::from_utf8_lossy(&st.stdout)
+        .lines()
+        .filter(|l| l.starts_with("A ") || l.starts_with("M "))
+        .filter_map(|l| l.get(3..))
+        .map(ToOwned::to_owned)
+        .collect();
+    Ok(names)
+}
+
 async fn git(dir: &Path, args: &[&str]) -> Result<()> {
     let out = lifecycle::git_command()
         .current_dir(dir)