Add quiet option to decrease log level

Language/Haskell/GhcMod.hs

@@ -12,6 +12,7 @@ module Language.Haskell.GhcMod (
   -- * Logging
   , GmLogLevel
   , increaseLogLevel
+  , decreaseLogLevel
   , gmSetLogLevel
   , gmLog
   -- * Types

Language/Haskell/GhcMod/Logging.hs

@@ -40,6 +40,10 @@ increaseLogLevel :: GmLogLevel -> GmLogLevel
 increaseLogLevel l | l == maxBound = l
 increaseLogLevel l = succ l
 
+decreaseLogLevel :: GmLogLevel -> GmLogLevel
+decreaseLogLevel l | l == minBound = l
+decreaseLogLevel l = succ l
+
 -- |
 -- >>> Just GmDebug <= Nothing
 -- False

src/GHCMod.hs

@@ -263,9 +263,14 @@ reqArg udsc dsc = ReqArg dsc udsc
 globalArgSpec :: [OptDescr (Options -> Options)]
 globalArgSpec =
       [ option "v" ["verbose"] "Can be given multiple times to be increasingly\
-                               \more verbose." $
+                               \ be more verbose." $
                NoArg $ \o -> o { logLevel = increaseLogLevel (logLevel o) }
 
+      , option "q" [] "Can be given multiple times to be increasingly be less\
+                      \ verbose." $
+               NoArg $ \o -> o { logLevel = decreaseLogLevel (logLevel o) }
+
+
       , option "l" ["tolisp"] "Format output as an S-Expression" $
                NoArg $ \o -> o { outputStyle = LispStyle }