huskies: merge 675_bug_mergemaster_silently_exits_when_feature_branch_has_zero_commits_ahead_of_master

server/src/agents/pool/pipeline/merge.rs

@@ -614,4 +614,165 @@ mod tests {
             MergeJobStatus::Running => panic!("should not still be running"),
         }
     }
+
+    // ── bug 675: zero commits ahead must fail with "no commits to merge" ─────
+
+    /// Regression test for bug 675: when the feature branch has zero commits
+    /// ahead of master the pipeline must fail with a clear "no commits to merge"
+    /// error and the story must remain in `4_merge` (not advance to `5_done`).
+    #[tokio::test]
+    async fn merge_agent_work_zero_commits_ahead_stays_in_merge_stage() {
+        use std::fs;
+        use tempfile::tempdir;
+
+        let tmp = tempdir().unwrap();
+        let repo = tmp.path();
+        init_git_repo(repo);
+
+        // Feature branch is created at the same commit as master — zero commits ahead.
+        Command::new("git")
+            .args(["checkout", "-b", "feature/story-675_zero_commits"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["checkout", "master"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+
+        // Place the story file in 4_merge so we can verify it stays there.
+        let merge_dir = repo.join(".huskies/work/4_merge");
+        fs::create_dir_all(&merge_dir).unwrap();
+        fs::write(
+            merge_dir.join("675_zero_commits.md"),
+            "---\nname: Zero commits test\n---\n",
+        )
+        .unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "-m", "place story in 4_merge"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+
+        let pool = Arc::new(AgentPool::new_test(3001));
+        let job = run_merge_to_completion(&pool, repo, "675_zero_commits").await;
+
+        // The job must have failed with a "no commits to merge" error.
+        match &job.status {
+            MergeJobStatus::Failed(e) => {
+                assert!(
+                    e.contains("no commits to merge"),
+                    "error must contain 'no commits to merge', got: {e}"
+                );
+                assert!(
+                    e.contains("675_zero_commits"),
+                    "error must name the story_id, got: {e}"
+                );
+            }
+            MergeJobStatus::Completed(report) => {
+                panic!(
+                    "expected Failed status, got Completed with success={}: {}",
+                    report.success, report.gate_output
+                );
+            }
+            MergeJobStatus::Running => panic!("should not still be running"),
+        }
+
+        // Story file must still be in 4_merge — NOT advanced to 5_done.
+        assert!(
+            merge_dir.join("675_zero_commits.md").exists(),
+            "story file must remain in 4_merge when merge fails"
+        );
+        assert!(
+            !repo
+                .join(".huskies/work/5_done/675_zero_commits.md")
+                .exists(),
+            "story must NOT advance to 5_done when merge fails with no commits"
+        );
+    }
+
+    /// Non-regression test for bug 675: a feature branch with exactly one commit
+    /// ahead of master must continue to merge successfully (happy path).
+    #[tokio::test]
+    async fn merge_agent_work_one_commit_ahead_merges_successfully() {
+        use std::fs;
+        use tempfile::tempdir;
+
+        let tmp = tempdir().unwrap();
+        let repo = tmp.path();
+        init_git_repo(repo);
+
+        // Feature branch: one commit ahead of master.
+        Command::new("git")
+            .args(["checkout", "-b", "feature/story-675_one_commit"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        fs::write(repo.join("feature_675.txt"), "feature content\n").unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "-m", "add feature file"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["checkout", "master"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+
+        // Place the story file in 4_merge.
+        let merge_dir = repo.join(".huskies/work/4_merge");
+        fs::create_dir_all(&merge_dir).unwrap();
+        fs::write(
+            merge_dir.join("675_one_commit.md"),
+            "---\nname: One commit test\n---\n",
+        )
+        .unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "-m", "place story in 4_merge"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+
+        let pool = Arc::new(AgentPool::new_test(3001));
+        let job = run_merge_to_completion(&pool, repo, "675_one_commit").await;
+
+        // The merge must not fail with "no commits to merge".
+        match &job.status {
+            MergeJobStatus::Failed(e) => {
+                assert!(
+                    !e.contains("no commits to merge"),
+                    "one-commit-ahead branch must NOT fail with 'no commits to merge': {e}"
+                );
+                // Gate failures (no script/test) are acceptable in test env.
+            }
+            MergeJobStatus::Completed(report) => {
+                // Success or gate failure — both acceptable; the key invariant is
+                // that we didn't fail with the zero-commits early-exit.
+                assert!(
+                    report.success || !report.gates_passed,
+                    "unexpected state: success={} gates_passed={}",
+                    report.success,
+                    report.gates_passed
+                );
+            }
+            MergeJobStatus::Running => panic!("should not still be running"),
+        }
+    }
 }