aider: Add --encoding argument and pass it to InputOutput.

# Aider chat conversation:

USER: add --encoding and pass it to `InputOutput`

ASSISTANT: To add the `--encoding` argument and pass it to `InputOutput`, we need to modify the `aider/main.py` file.

Here are the steps:

1. Add a new argument `--encoding` to the `argparse.ArgumentParser` in the `main` function.
2. Pass the `args.encoding` to the `InputOutput` class instantiation.

Here are the changes:

```python
aider/main.py
<<<<<<< HEAD
    ##########
    other_group = parser.add_argument_group("Other Settings")
    other_group.add_argument(
        "--version",
        action="version",
        version=f"%(prog)s {__version__}",
        help="Show the version number and exit",
    )
    other_group.add_argument(
        "--apply",
        metavar="FILE",
        help="Apply the changes from the given file instead of running the chat (debug)",
    )
    other_group.add_argument(
        "--yes",
        action="store_true",
        help="Always say yes to every confirmation",
        default=None,
    )
    other_group.add_argument(
        "-v",
        "--verbose",
        action="store_true",
        help="Enable verbose output",
        default=False,
    )
    other_group.add_argument(
        "--show-repo-map",
        action="store_true",
        help="Print the repo map and exit (debug)",
        default=False,
    )
    other_group.add_argument(
        "--message",
        "--msg",
        "-m",
        metavar="COMMAND",
        help="Specify a single message to send GPT, process reply then exit (disables chat mode)",
    )
    other_group.add_argument(
        "-c",
        "--config",
        is_config_file=True,
        metavar="CONFIG_FILE",
        help=(
            "Specify the config file (default: search for .aider.conf.yml in git root, cwd"
            " or home directory)"
        ),
    )

    args = parser.parse_args(argv)
=======
    ##########
    other_group = parser.add_argument_group("Other Settings")
    other_group.add_argument(
        "--version",
        action="version",
        version=f"%(prog)s {__version__}",
        help="Show the version number and exit",
    )
    other_group.add_argument(
        "--apply",
        metavar="FILE",
        help="Apply the changes from the given file instead of running the chat (debug)",
    )
    other_group.add_argument(
        "--yes",
        action="store_true",
        help="Always say yes to every confirmation",
        default=None,
    )
    other_group.add_argument(
        "-v",
        "--verbose",
        action="store_true",
        help="Enable verbose output",
        default=False,
    )
    other_group.add_argument(
        "--show-repo-map",
        action="store_true",
        help="Print the repo map and exit (debug)",
        default=False,
    )
    other_group.add_argument(
        "--message",
        "--msg",
        "-m",
        metavar="COMMAND",
        help="Specify a single message to send GPT, process reply then exit (disables chat mode)",
    )
    other_group.add_argument(
        "--encoding",
        default="utf-8",
        help="Specify the encoding for input and output (default: utf-8)",
    )
    other_group.add_argument(
        "-c",
        "--config",
        is_config_file=True,
        metavar="CONFIG_FILE",
        help=(
            "Specify the config file (default: search for .aider.conf.yml in git root, cwd"
            " or home directory)"
        ),
    )

    args = parser.parse_args(argv)
>>>>>>> updated
```

```python
aider/main.py
<<<<<<< HEAD
    io = InputOutput(
        args.pretty,
        args.yes,
        args.input_history_file,
        args.chat_history_file,
        input=input,
        output=output,
        user_input_color=args.user_input_color,
        tool_output_color=args.tool_output_color,
        tool_error_color=args.tool_error_color,
        dry_run=args.dry_run,
    )
=======
    io = InputOutput(
        args.pretty,
        args.yes,
        args.input_history_file,
        args.chat_history_file,
        input=input,
        output=output,
        user_input_color=args.user_input_color,
        tool_output_color=args.tool_output_color,
        tool_error_color=args.tool_error_color,
        dry_run=args.dry_run,
        encoding=args.encoding,
    )
>>>>>>> updated
```

Please note that the `InputOutput` class should be able to handle the `encoding` argument. If it's not the case, we need to modify the `InputOutput` class as well.

aider/main.py

@@ -378,6 +378,11 @@ def main(argv=None, input=None, output=None, force_git_root=None):
         metavar="COMMAND",
         help="Specify a single message to send GPT, process reply then exit (disables chat mode)",
     )
+    other_group.add_argument(
+        "--encoding",
+        default="utf-8",
+        help="Specify the encoding for input and output (default: utf-8)",
+    )
     other_group.add_argument(
         "-c",
         "--config",
@@ -414,6 +419,7 @@ def main(argv=None, input=None, output=None, force_git_root=None):
         tool_output_color=args.tool_output_color,
         tool_error_color=args.tool_error_color,
         dry_run=args.dry_run,
+        encoding=args.encoding,
     )
 
     fnames = [str(Path(fn).resolve()) for fn in args.files]