refactor cli entrypoint

src/postcar/__main__.py

@@ -1,21 +1,5 @@
-import asyncio
-from postcar.__about__ import __version__
-from postcar.cli import handlers, parser
+import sys
+from postcar.cli import main
 
 
-args = parser.parse_args()
-
-
-if args.version:
-    print(__version__)
-    exit(0)
-
-if args.command is None:
-    parser.print_help()
-    exit(1)
-
-if (handler := handlers.get(args.command)) is None:
-    print(f"handler for '{args.command}' not found")
-    exit(1)
-
-asyncio.run(handler(args=args))
+sys.exit(main())

src/postcar/cli/__init__.py

@@ -1,4 +1,6 @@
+import asyncio
 import typing as t
+from postcar.__about__ import __version__
 from postcar.cli import migrate
 from postcar.cli._parser import parser, subparsers
 
@@ -15,7 +17,25 @@
 )
 
 
+def main() -> t.Optional[int]:
+    args = parser.parse_args()
+
+    if args.version:
+        return print(__version__)
+
+    if args.command is None:
+        parser.print_help()
+        return 1
+
+    if (handler := handlers.get(args.command)) is None:
+        print(f"handler for '{args.command}' not found")
+        return 2
+
+    return asyncio.run(handler(args=args))
+
+
 __all__ = (
+    "main",
     "parser",
     "handlers",
 )