cli: warning on app add (#28619)

instead of #28128

libs/cli/langchain_cli/namespaces/app.py

@@ -5,6 +5,7 @@
 import shutil
 import subprocess
 import sys
+import warnings
 from pathlib import Path
 from typing import Dict, List, Optional, Tuple
 
@@ -163,6 +164,12 @@ def add(
     langchain app add git+ssh://[email protected]/efriis/simple-pirate.git
     """
 
+    if not branch and not repo:
+        warnings.warn(
+            "Adding templates from the default branch and repo is deprecated."
+            " At a minimum, you will have to add `--branch v0.2` for this to work"
+        )
+
     parsed_deps = parse_dependencies(dependencies, repo, branch, api_path)
 
     project_root = get_package_root(project_dir)