refuse a dependency add of an issue on itself

hive-forge/src/verbs/dependency.rs

@@ -202,6 +202,11 @@ fn apply_and_verify(
 /// `Internal Server Error`) and accepts longer cycles without complaint,
 /// so the check walks `dependency list` client-side.
 fn refuse_cycle(client: &Client, owner: &str, name: &str, number: u64, dep: u64) -> Result<()> {
+    if dep == number {
+        bail!(
+            "hive-forge dependency add: #{number} cannot depend on itself, which would create a cycle"
+        );
+    }
     let path = find_dependency_path(dep, number, |n| {
         let deps = dependency_summaries(client, owner, name, n)?;
         Ok(deps

hive-forge/tests/dependency_cycle.rs

@@ -149,3 +149,17 @@ fn non_cyclic_add_reaches_the_forge() {
 fn tag(n: u64) -> String {
     format!("{}{n}", '#')
 }
+
+#[test]
+fn self_dependency_is_refused_before_any_post() {
+    let (ok, stderr, posts) = add("self", "10", "10");
+    assert!(!ok);
+    assert!(
+        stderr.contains(&format!(
+            "{} cannot depend on itself, which would create a cycle",
+            tag(10)
+        )),
+        "{stderr}"
+    );
+    assert_eq!(posts, 0);
+}