improve global options display in --help

Put them in the help of subcommands, not the main command.

And, hide them from the synopsis, to avoid cluttering it.

CmdLine/GlobalSetter.hs

@@ -0,0 +1,24 @@
+{- git-annex global options
+ -
+ - Copyright 2015 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+  -}
+  
+module CmdLine.GlobalSetter where
+
+import Types.DeferredParse
+import Common
+import Annex
+
+import Options.Applicative
+
+globalFlag :: Annex () -> Mod FlagFields GlobalSetter -> Parser GlobalSetter
+globalFlag setter = flag' (DeferredParse setter) 
+
+globalSetter :: (v -> Annex ()) -> Parser v -> Parser GlobalSetter
+globalSetter setter parser = DeferredParse . setter <$> parser
+
+combineGlobalSetters :: [Parser GlobalSetter] -> Parser GlobalSetter
+combineGlobalSetters l = DeferredParse . sequence_ . map getParsed
+	<$> many (foldl1 (<|>) l)