help: Let OptionParser generate help text for supported commands

Library/Homebrew/dev-cmd/prof.rb

@@ -1,7 +1,7 @@
 #:  * `prof` [ruby options]:
 #:    Run Homebrew with the Ruby profiler.
 #:    For example:
-#       brew prof readall
+#:       brew prof readall
 
 module Homebrew
   module_function

Library/Homebrew/help.rb

@@ -38,8 +38,13 @@ module Homebrew
     module_function
 
     def help(cmd = nil, flags = {})
-      # Let OptionParser generate help text for developer commands
-      return if require? HOMEBREW_LIBRARY_PATH/"dev-cmd"/cmd
+      # Let OptionParser generate help text for commands which have a parser defined
+      begin
+        Homebrew.send("#{cmd.gsub('-','_')}_args".to_sym)
+        return
+      rescue NoMethodError
+        nil
+      end
 
       # Resolve command aliases and find file containing the implementation.
       if cmd