chg: dev: add main module.

beets/__main__.py

@@ -0,0 +1,6 @@
+"""main module."""
+import sys
+from .ui import main
+
+if __name__ == "__main__":
+    main(sys.argv[1:])

beets/ui/__init__.py

@@ -946,6 +946,16 @@ class SubcommandsOptionParser(CommonOptionsParser):
 
         self.subcommands = []
 
+    def get_prog_name(self):
+        """Get program name.
+
+        Returns:
+            Program name.
+        """
+        prog_name = super(SubcommandsOptionParser, self).get_prog_name()
+        prog_name = 'beets' if prog_name == '__main__.py' else prog_name
+        return prog_name
+
     def add_subcommand(self, *cmds):
         """Adds a Subcommand object to the parser's list of commands.
         """