Fix arg parser help message display (#1247)

* Fix arg parser help message display

* Add unittest

tests/test_arg_parser.py

@@ -0,0 +1,42 @@
+from opendevin.config import get_parser
+
+import pytest
+
+
+def test_help_message(capsys):
+    parser = get_parser()
+    with pytest.raises(SystemExit):  # `--help` causes SystemExit
+        parser.parse_args(['--help'])
+    captured = capsys.readouterr()
+    expected_help_message = """
+usage: pytest [-h] [-d DIRECTORY] [-t TASK] [-f FILE] [-c AGENT_CLS]
+[-m MODEL_NAME] [-i MAX_ITERATIONS] [-n MAX_CHARS]
+
+Run an agent with a specific task
+
+options:
+  -h, --help            show this help message and exit
+  -d DIRECTORY, --directory DIRECTORY
+                        The working directory for the agent
+  -t TASK, --task TASK  The task for the agent to perform
+  -f FILE, --file FILE  Path to a file containing the task. Overrides -t if
+  both are provided.
+  -c AGENT_CLS, --agent-cls AGENT_CLS
+                        The agent class to use
+  -m MODEL_NAME, --model-name MODEL_NAME
+                        The (litellm) model name to use
+  -i MAX_ITERATIONS, --max-iterations MAX_ITERATIONS
+                        The maximum number of iterations to run the agent
+  -n MAX_CHARS, --max-chars MAX_CHARS
+                        The maximum number of characters to send to and
+                        receive from LLM per task
+"""
+    actual_lines = captured.out.strip().split('\n')
+    expected_lines = expected_help_message.strip().split('\n')
+
+    # Ensure both outputs have the same number of lines
+    assert len(actual_lines) == len(expected_lines), 'The number of lines in the help message does not match.'
+
+    # Compare each line
+    for actual, expected in zip(actual_lines, expected_lines):
+        assert actual.strip() == expected.strip(), f"Expected '{expected}', got '{actual}'"