refuse a dependency add of an issue on itself

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);
+}