aider: Add a test case to reproduce the issue of trying to add a directory using the /add command.

# Aider chat conversation:

USER: add a test case to reproduce this issue: Trying to add just a directory makes the program throw the following and exit:

> /add src/components

Traceback (most recent call last):
  File "/home/palmerd/.local/bin/aider", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/main.py", line 369, in main
    coder.run()
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/coders/base_coder.py", line 382, in run
    new_user_message = self.run_loop()
                       ^^^^^^^^^^^^^^^
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/coders/base_coder.py", line 446, in run_loop
    return self.commands.run(inp)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/commands.py", line 60, in run
    return self.do_run(matching_commands[0][1:], rest_inp)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/commands.py", line 45, in do_run
    return cmd_method(args)
           ^^^^^^^^^^^^^^^^
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/commands.py", line 264, in cmd_add
    content = self.io.read_text(abs_file_path)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/palmerd/.local/lib/python3.11/site-packages/aider/io.py", line 142, in read_text
    with open(str(filename), "r", encoding=self.encoding) as f:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
IsADirectoryError: [Errno 21] Is a directory: '/home/palmerd/vue-frontend/src/components'

ASSISTANT: To reproduce this issue, we need to create a test case that tries to add a directory using the `/add` command. However, the code you've provided is not designed to handle test cases.

Could you please provide the test suite or the file where the test cases are written so that I can add a new test case?

USER: I added these *read-write* files: tests/test_commands.py

ASSISTANT: Great, we can add a test case in the `tests/test_commands.py` file. This test case will attempt to add a directory and check if the appropriate error is handled.

Here is the proposed change:

```python
tests/test_commands.py
<<<<<<< ORIGINAL
    def test_cmd_add_no_match(self):
        # Initialize the Commands and InputOutput objects
        io = InputOutput(pretty=False, yes=True)
        from aider.coders import Coder

        coder = Coder.create(models.GPT35, None, io, openai_api_key="deadbeef")
        commands = Commands(io, coder)

        # Call the cmd_add method with a non-existent file pattern
        commands.cmd_add("*.nonexistent")

        # Check if no files have been added to the chat session
        self.assertEqual(len(coder.abs_fnames), 0)
=======
    def test_cmd_add_no_match(self):
        # Initialize the Commands and InputOutput objects
        io = InputOutput(pretty=False, yes=True)
        from aider.coders import Coder

        coder = Coder.create(models.GPT35, None, io, openai_api_key="deadbeef")
        commands = Commands(io, coder)

        # Call the cmd_add method with a non-existent file pattern
        commands.cmd_add("*.nonexistent")

        # Check if no files have been added to the chat session
        self.assertEqual(len(coder.abs_fnames), 0)

    def test_cmd_add_directory(self):
        # Initialize the Commands and InputOutput objects
        io = InputOutput(pretty=False, yes=True)
        from aider.coders import Coder

        coder = Coder.create(models.GPT35, None, io, openai_api_key="deadbeef")
        commands = Commands(io, coder)

        # Create a directory
        os.mkdir("test_dir")

        # Call the cmd_add method with a directory
        with self.assertRaises(IsADirectoryError):
            commands.cmd_add("test_dir")
>>>>>>> UPDATED
```

This new test case `test_cmd_add_directory` creates a directory named `test_dir` and attempts to add it using the `cmd_add` method. We expect an `IsADirectoryError` to be raised in this scenario.

tests/test_commands.py

@@ -79,6 +79,21 @@ class TestCommands(TestCase):
         # Check if no files have been added to the chat session
         self.assertEqual(len(coder.abs_fnames), 0)
 
+    def test_cmd_add_directory(self):
+        # Initialize the Commands and InputOutput objects
+        io = InputOutput(pretty=False, yes=True)
+        from aider.coders import Coder
+
+        coder = Coder.create(models.GPT35, None, io, openai_api_key="deadbeef")
+        commands = Commands(io, coder)
+
+        # Create a directory
+        os.mkdir("test_dir")
+
+        # Call the cmd_add method with a directory
+        with self.assertRaises(IsADirectoryError):
+            commands.cmd_add("test_dir")
+
     def test_cmd_drop_with_glob_patterns(self):
         # Initialize the Commands and InputOutput objects
         io = InputOutput(pretty=False, yes=True)