feat: add --shell-completions arg for shell completion scripts

aider/args.py

@@ -811,6 +811,18 @@ def get_parser(default_config_files, git_root):
         help="Specify which editor to use for the /editor command",
     )
 
+    supported_shells_list = sorted(list(shtab.SUPPORTED_SHELLS))
+    group.add_argument(
+        "--shell-completions",
+        metavar="SHELL",
+        choices=supported_shells_list,
+        help=(
+            "Print shell completion script for the specified SHELL and exit. Supported shells:"
+            f" {', '.join(supported_shells_list)}. Example: aider --shell-completions bash"
+        ),
+    )
+
+
     ##########
     group = parser.add_argument_group("Deprecated model settings")
     # Add deprecated model shortcut arguments

aider/main.py

@@ -15,6 +15,7 @@ except ImportError:
 
 import importlib_resources
 from dotenv import load_dotenv
+import shtab
 from prompt_toolkit.enums import EditingMode
 
 from aider import __version__, models, urls, utils
@@ -502,6 +503,13 @@ def main(argv=None, input=None, output=None, force_git_root=None, return_coder=F
     # Parse again to include any arguments that might have been defined in .env
     args = parser.parse_args(argv)
 
+    if args.shell_completions:
+        # Ensure parser.prog is set for shtab, though it should be by default
+        parser.prog = "aider"
+        print(shtab.complete(parser, shell=args.shell_completions))
+        sys.exit(0)
+
+
     if git is None:
         args.git = False