Add support for VI editing mode in the terminal.

aider/args.py

@@ -21,6 +21,11 @@ def get_parser(default_config_files, git_root):
     )
     group = parser.add_argument_group("Main")
     group.add_argument(
+        "--vim",
+        action="store_true",
+        help="Use VI editing mode in the terminal (default: False)",
+        default=False,
+    )
         "files",
         metavar="FILE",
         nargs="*",

aider/main.py

@@ -258,8 +258,11 @@ def main(argv=None, input=None, output=None, force_git_root=None, return_coder=F
         tool_error_color=args.tool_error_color,
         dry_run=args.dry_run,
         encoding=args.encoding,
+        editingmode=editing_mode,
     )
 
+    editing_mode = EditingMode.VI if args.vim else EditingMode.EMACS
+
     fnames = [str(Path(fn).resolve()) for fn in args.files]
     if len(args.files) > 1:
         good = True