Create dummy brew cmd

Library/Homebrew/abstract_command.rb

@@ -62,4 +62,9 @@ module Homebrew
     sig { abstract.void }
     def run; end
   end
+
+  module Cmd
+    # The command class for `brew` itself, allowing its args to be parsed.
+    class Brew < AbstractCommand; end
+  end
 end

Library/Homebrew/brew.rb

@@ -48,7 +48,7 @@ begin
   ARGV.delete_at(help_cmd_index) if help_cmd_index
 
   require "cli/parser"
-  args = Homebrew::CLI::Parser.new.parse(ARGV.dup.freeze, ignore_invalid_options: true)
+  args = Homebrew::CLI::Parser.new(Homebrew::Cmd::Brew).parse(ARGV.dup.freeze, ignore_invalid_options: true)
   Context.current = args.context
 
   path = PATH.new(ENV.fetch("PATH"))

Library/Homebrew/cli/parser.rb

@@ -167,15 +167,12 @@ module Homebrew
           @command_name = T.let(T.must(cmd_location.label).chomp("_args").tr("_", "-"), String)
           @is_dev_cmd = T.let(T.must(cmd_location.absolute_path).start_with?(Commands::HOMEBREW_DEV_CMD_PATH),
                               T::Boolean)
-          # We allow this path only from `brew.rb`:
-          if @command_name != "<main>"
           odeprecated(
             "`brew #{@command_name}', which does not inherit from from Homebrew::AbstractCommand. This command " \
             "needs to be refactored, as it is written in a style that",
             disable_for_developers: false,
           )
         end
-        end
 
         @constraints = T.let([], T::Array[[String, String]])
         @conflicts = T.let([], T::Array[T::Array[String]])