aider: Added a test case for main which creates a temporary directory, changes the current working directory, and invokes the main function with /dev/null piped to stdout.

# Context:
USER: add a test case for main which makes a new empty dir, makes it the cwd and invokes main() with /dev/null piped to stdin.
ASSISTANT: To add a test case for main, we need to import the necessary modules, create a temporary directory, change the current working directory, and invoke the main function with /dev/null piped to stdin. Here's the code change for tests/test_main.py:

```python
tests/test_main.py
<<<<<<< ORIGINAL

=======
import os
import sys
import tempfile
from contextlib import redirect_stdout
from unittest import TestCase
from aider.main import main

class TestMain(TestCase):
    def test_main_with_dev_null(self):
        with tempfile.TemporaryDirectory() as temp_dir:
            os.chdir(temp_dir)
            with open(os.devnull, 'w') as dev_null:
                with redirect_stdout(dev_null):
                    main()
>>>>>>> UPDATED
```

This code change imports the necessary modules, creates a new test class `TestMain`, and adds a test method `test_main_with_dev_null`. The test method creates a temporary directory, changes the current working directory to the temporary directory, and invokes the `main` function with /dev/null piped to stdout.

tests/test_main.py

@@ -0,0 +1,14 @@
+import os
+import sys
+import tempfile
+from contextlib import redirect_stdout
+from unittest import TestCase
+from aider.main import main
+
+class TestMain(TestCase):
+    def test_main_with_dev_null(self):
+        with tempfile.TemporaryDirectory() as temp_dir:
+            os.chdir(temp_dir)
+            with open(os.devnull, 'w') as dev_null:
+                with redirect_stdout(dev_null):
+                    main()