brew.rb: update help parsing

Library/Homebrew/brew.rb

@@ -32,20 +32,17 @@ begin
 
   empty_argv = ARGV.empty?
   help_flag_list = %w[-h --help --usage -?]
-  help_flag = false
+  help_flag = !ENV["HOMEBREW_HELP"].nil?
   internal_cmd = true
   cmd = nil
 
   ARGV.dup.each_with_index do |arg, i|
     break if help_flag && cmd
 
-    if help_flag_list.include?(arg)
-      # Option-style help: Both `--help <cmd>` and `<cmd> --help` are fine.
-      help_flag = true
-    elsif arg == "help" && !cmd
+    if arg == "help" && !cmd
       # Command-style help: `help <cmd>` is fine, but `<cmd> help` is not.
       help_flag = true
-    elsif !cmd
+    elsif !cmd && !help_flag_list.include?(arg)
       cmd = ARGV.delete_at(i)
     end
   end