[misc] improve entrypoint (#7345)

* 纯粹优化下入口代码，因为看到if else太多了

* Update cli.py

---------

Co-authored-by: hoshi-hiyouga <hiyouga@buaa.edu.cn>

src/llamafactory/cli.py

@@ -17,9 +17,11 @@ import subprocess
 import sys
 from copy import deepcopy
 from enum import Enum, unique
+from functools import partial
 
 from .extras import logging
 
+
 USAGE = (
     "-" * 70
     + "\n"
@@ -38,19 +40,6 @@ USAGE = (
 logger = logging.get_logger(__name__)
 
 
-@unique
-class Command(str, Enum):
-    API = "api"
-    CHAT = "chat"
-    ENV = "env"
-    EVAL = "eval"
-    EXPORT = "export"
-    TRAIN = "train"
-    WEBDEMO = "webchat"
-    WEBUI = "webui"
-    VER = "version"
-    HELP = "help"
-
 def main():
     from . import launcher
     from .api.app import run_api
@@ -73,20 +62,22 @@ def main():
         + "-" * 58
     )
 
-    command = sys.argv.pop(1) if len(sys.argv) != 1 else Command.HELP
-    if command == Command.API:
-        run_api()
-    elif command == Command.CHAT:
-        run_chat()
-    elif command == Command.ENV:
-        print_env()
-    elif command == Command.EVAL:
-        run_eval()
-    elif command == Command.EXPORT:
-        export_model()
-    elif command == Command.TRAIN:
+    COMMANDS = {
+        "api": run_api,
+        "chat": run_chat,
+        "env": print_env,
+        "eval": run_eval,
+        "export": export_model,
+        "train": run_exp,
+        "webchat": run_web_demo,
+        "webui": run_web_ui,
+        "version": partial(print, WELCOME),
+        "help": partial(print, USAGE),
+    }
+
+    command = sys.argv.pop(1) if len(sys.argv) != 1 else "help"
     force_torchrun = is_env_enabled("FORCE_TORCHRUN")
-        if force_torchrun or (get_device_count() > 1 and not use_ray()):
+    if command == "train" and (force_torchrun or (get_device_count() > 1 and not use_ray())):
         nnodes = os.getenv("NNODES", "1")
         node_rank = os.getenv("NODE_RANK", "0")
         nproc_per_node = os.getenv("NPROC_PER_NODE", str(get_device_count()))
@@ -123,17 +114,7 @@ def main():
         )
         sys.exit(process.returncode)
     else:
-            run_exp()
-    elif command == Command.WEBDEMO:
-        run_web_demo()
-    elif command == Command.WEBUI:
-        run_web_ui()
-    elif command == Command.VER:
-        print(WELCOME)
-    elif command == Command.HELP:
-        print(USAGE)
-    else:
-        print(f"Unknown command: {command}.\n{USAGE}")
+        COMMANDS[command]()
 
 
 if __name__ == "__main__":