Make the configure command take the defaults from the config file

Just like the install command has always done. This makes them consistent.
So by default that means cabal configure uses --user --prefix=$HOME/.cabal

Hackage/Setup.hs

@@ -12,6 +12,7 @@
 -----------------------------------------------------------------------------
 module Hackage.Setup
     ( globalCommand, Cabal.GlobalFlags(..)
+    , configureCommand
     , installCommand --Cabal.InstallFlags(..)
     , listCommand
     , updateCommand
@@ -61,6 +62,11 @@ globalCommand = Cabal.globalCommand {
       ++ "\nSee http://www.haskell.org/cabal/ for more information.\n"
   }
 
+configureCommand :: CommandUI Cabal.ConfigFlags
+configureCommand = (Cabal.configureCommand defaultProgramConfiguration) {
+    commandDefaultFlags = mempty
+  }
+
 installCommand :: CommandUI Cabal.ConfigFlags
 installCommand = (Cabal.configureCommand defaultProgramConfiguration) {
     commandName         = "install",

Main.hs

@@ -78,15 +78,15 @@ mainWorker args =
                                   ++ " of the Cabal library "
 
     commands =
-      [installCommand         `commandAddAction` installAction
+      [configureCommand       `commandAddAction` configureAction
+      ,installCommand         `commandAddAction` installAction
       ,infoCommand            `commandAddAction` infoAction
       ,listCommand            `commandAddAction` listAction
       ,updateCommand          `commandAddAction` updateAction
       ,upgradeCommand         `commandAddAction` upgradeAction
       ,fetchCommand           `commandAddAction` fetchAction
       ,uploadCommand          `commandAddAction` uploadAction
 
-      ,wrapperAction (Cabal.configureCommand defaultProgramConfiguration)
       ,wrapperAction (Cabal.buildCommand     defaultProgramConfiguration)
       ,wrapperAction Cabal.copyCommand
       ,wrapperAction Cabal.haddockCommand
@@ -106,6 +106,17 @@ wrapperAction command =
   let args = commandName command : commandShowOptions command flags ++ extraArgs
    in setupWrapper args Nothing
 
+configureAction :: Cabal.ConfigFlags -> [String] -> IO ()
+configureAction flags extraArgs = do
+  configFile <- defaultConfigFile --FIXME
+  let verbosity = fromFlagOrDefault normal (Cabal.configVerbose flags)
+  config <- loadConfig verbosity configFile
+  let flags' = savedConfigToConfigFlags (Cabal.configPackageDB flags) config
+               `mappend` flags
+      args = commandName configureCommand
+           : commandShowOptions configureCommand flags' ++ extraArgs
+  setupWrapper args Nothing
+
 installAction :: Cabal.ConfigFlags -> [String] -> IO ()
 installAction flags extraArgs = do
   pkgs <- either die return (parsePackageArgs extraArgs)