overlay config .git only when the source has one; record a failed start in the op output

hive-c0re/src/lifecycle/mod.rs

@@ -801,6 +801,21 @@ fn make_log_callback(
     }
 }
 
+/// Put a failed non-streaming op's error into its build-log row, which has no
+/// other output: `start` runs through `call`, not the streaming protocol. The
+/// error carries `nixos-container`'s stderr.
+fn record_failure(
+    logs: Option<&crate::build_logs::BuildLogs>,
+    log_id: Option<i64>,
+    err: &anyhow::Error,
+) {
+    if let (Some(h), Some(id)) = (logs, log_id) {
+        for line in format!("{err:#}").lines() {
+            h.append_stderr(id, line);
+        }
+    }
+}
+
 /// A `create` or `update` asked for without a closure. The
 /// public entry points take the closure, so this guards the string dispatch
 /// below only.
@@ -867,7 +882,13 @@ async fn priv_run_inner(
             }
             None => Err(missing_toplevel(kind, name)),
         },
-        "start" => crate::priv_client::start_container(name).await,
+        "start" => {
+            let started = crate::priv_client::start_container(name).await;
+            if let Err(e) = &started {
+                record_failure(logs.as_deref(), log_id, e);
+            }
+            started
+        }
         "stop" => crate::priv_client::stop_container(name).await,
         "kill" => crate::priv_client::kill_container(name).await,
         "destroy" => crate::priv_client::destroy_container(name).await,

hive-c0re/src/lifecycle/tests.rs

@@ -514,3 +514,20 @@ fn hive_facts_leave_unset_values_out() {
     assert_eq!(facts.egress_no_proxy, None);
     assert_eq!(facts.name, None);
 }
+
+/// A failed `start` leaves its error in the op's build-log row; without it the
+/// row is empty. A missing row id records nothing and does not panic.
+#[test]
+fn a_failed_start_puts_its_error_in_the_op_output() {
+    let dir = tempfile::tempdir().expect("tempdir");
+    let logs = crate::build_logs::BuildLogs::open(dir.path()).expect("open");
+    let id = logs
+        .start("updo", "start", "nixos-container start h-updo", None)
+        .expect("start");
+    let err = anyhow::anyhow!("nixos-container start h-updo failed (exit status: 1): Job failed");
+    record_failure(Some(&logs), Some(id), &err);
+    let full = logs.get_full(id).expect("get").expect("row");
+    assert!(full.stderr.contains("Job failed"), "{}", full.stderr);
+    record_failure(Some(&logs), None, &err);
+    record_failure(None, Some(id), &err);
+}