Derive some additional Generic instances (cabal-install)

This is preparatory work for implementing #3169
it's kept in a different commit in order to facilitate
comparing code-generation.

cabal-install/Distribution/Client/Config.hs

 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveGeneric #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -140,6 +141,7 @@ import Data.Function
          ( on )
 import Data.List
          ( nubBy )
+import GHC.Generics ( Generic )
 
 --
 -- * Configuration saved in the config file
@@ -155,7 +157,7 @@ data SavedConfig = SavedConfig {
     savedUploadFlags       :: UploadFlags,
     savedReportFlags       :: ReportFlags,
     savedHaddockFlags      :: HaddockFlags
-  }
+  } deriving Generic
 
 instance Monoid SavedConfig where
   mempty = SavedConfig {

cabal-install/Distribution/Client/GlobalFlags.hs

 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE ExistentialQuantification #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -44,6 +45,7 @@ import qualified Data.Map as Map
 import Data.Monoid
          ( Monoid(..) )
 #endif
+import GHC.Generics ( Generic )
 
 import qualified Hackage.Security.Client                    as Sec
 import qualified Hackage.Security.Util.Path                 as Sec
@@ -73,7 +75,7 @@ data GlobalFlags = GlobalFlags {
     globalIgnoreSandbox     :: Flag Bool,
     globalIgnoreExpiry      :: Flag Bool,    -- ^ Ignore security expiry dates
     globalHttpTransport     :: Flag String
-  }
+  } deriving Generic
 
 defaultGlobalFlags :: GlobalFlags
 defaultGlobalFlags  = GlobalFlags {

cabal-install/Distribution/Client/Init/Types.hs

 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveGeneric #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Distribution.Client.Init.Types
@@ -32,6 +34,7 @@ import Distribution.Text
 #if !MIN_VERSION_base(4,8,0)
 import Data.Monoid (Monoid(..))
 #endif
+import GHC.Generics (Generic)
 
 -- | InitFlags is really just a simple type to represent certain
 --   portions of a .cabal file.  Rather than have a flag for EVERY
@@ -72,7 +75,7 @@ data InitFlags =
               , initVerbosity :: Flag Verbosity
               , overwrite     :: Flag Bool
               }
-  deriving (Show)
+  deriving (Show, Generic)
 
   -- the Monoid instance for Flag has later values override earlier
   -- ones, which is why we want Maybe [foo] for collecting foo values,

cabal-install/Distribution/Client/Sandbox/PackageEnvironment.hs

 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveGeneric #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Distribution.Client.Sandbox.PackageEnvironment
@@ -76,6 +78,7 @@ import qualified Text.PrettyPrint          as Disp
 import qualified Distribution.Compat.ReadP as Parse
 import qualified Distribution.ParseUtils   as ParseUtils ( Field(..) )
 import qualified Distribution.Text         as Text
+import GHC.Generics ( Generic )
 
 
 --
@@ -89,7 +92,7 @@ data PackageEnvironment = PackageEnvironment {
   -- for constructing nested sandboxes (see discussion in #1196).
   pkgEnvInherit       :: Flag FilePath,
   pkgEnvSavedConfig   :: SavedConfig
-}
+} deriving Generic
 
 instance Monoid PackageEnvironment where
   mempty = PackageEnvironment {

cabal-install/Distribution/Client/Setup.hs

@@ -503,7 +503,7 @@ data SkipAddSourceDepsCheck =
 
 data BuildExFlags = BuildExFlags {
   buildOnly     :: Flag SkipAddSourceDepsCheck
-}
+} deriving Generic
 
 buildExOptions :: ShowOrParseArgs -> [OptionField BuildExFlags]
 buildExOptions _showOrParseArgs =
@@ -894,7 +894,7 @@ data ReportFlags = ReportFlags {
     reportUsername  :: Flag Username,
     reportPassword  :: Flag Password,
     reportVerbosity :: Flag Verbosity
-  }
+  } deriving Generic
 
 defaultReportFlags :: ReportFlags
 defaultReportFlags = ReportFlags {
@@ -954,7 +954,7 @@ data GetFlags = GetFlags {
     getPristine         :: Flag Bool,
     getSourceRepository :: Flag (Maybe RepoKind),
     getVerbosity        :: Flag Verbosity
-  }
+  } deriving Generic
 
 defaultGetFlags :: GetFlags
 defaultGetFlags = GetFlags {
@@ -1039,7 +1039,7 @@ data ListFlags = ListFlags {
     listSimpleOutput :: Flag Bool,
     listVerbosity    :: Flag Verbosity,
     listPackageDBs   :: [Maybe PackageDB]
-  }
+  } deriving Generic
 
 defaultListFlags :: ListFlags
 defaultListFlags = ListFlags {
@@ -1119,7 +1119,7 @@ instance Semigroup ListFlags where
 data InfoFlags = InfoFlags {
     infoVerbosity  :: Flag Verbosity,
     infoPackageDBs :: [Maybe PackageDB]
-  }
+  } deriving Generic
 
 defaultInfoFlags :: InfoFlags
 defaultInfoFlags = InfoFlags {
@@ -1520,7 +1520,7 @@ data UploadFlags = UploadFlags {
     uploadPassword    :: Flag Password,
     uploadPasswordCmd :: Flag [String],
     uploadVerbosity   :: Flag Verbosity
-  }
+  } deriving Generic
 
 defaultUploadFlags :: UploadFlags
 defaultUploadFlags = UploadFlags {
@@ -1792,7 +1792,7 @@ initCommand = CommandUI {
 data SDistExFlags = SDistExFlags {
     sDistFormat    :: Flag ArchiveFormat
   }
-  deriving Show
+  deriving (Show, Generic)
 
 data ArchiveFormat = TargzFormat | ZipFormat -- | ...
   deriving (Show, Eq)
@@ -1843,7 +1843,7 @@ instance Semigroup SDistExFlags where
 
 data Win32SelfUpgradeFlags = Win32SelfUpgradeFlags {
   win32SelfUpgradeVerbosity :: Flag Verbosity
-}
+} deriving Generic
 
 defaultWin32SelfUpgradeFlags :: Win32SelfUpgradeFlags
 defaultWin32SelfUpgradeFlags = Win32SelfUpgradeFlags {
@@ -1883,7 +1883,7 @@ instance Semigroup Win32SelfUpgradeFlags where
 
 data ActAsSetupFlags = ActAsSetupFlags {
     actAsSetupBuildType :: Flag BuildType
-}
+} deriving Generic
 
 defaultActAsSetupFlags :: ActAsSetupFlags
 defaultActAsSetupFlags = ActAsSetupFlags {
@@ -1930,7 +1930,7 @@ data SandboxFlags = SandboxFlags {
   sandboxSnapshot  :: Flag Bool, -- FIXME: this should be an 'add-source'-only
                                  -- flag.
   sandboxLocation  :: Flag FilePath
-}
+} deriving Generic
 
 defaultSandboxLocation :: FilePath
 defaultSandboxLocation = ".cabal-sandbox"
@@ -2058,7 +2058,7 @@ instance Semigroup SandboxFlags where
 
 data ExecFlags = ExecFlags {
   execVerbosity :: Flag Verbosity
-}
+} deriving Generic
 
 defaultExecFlags :: ExecFlags
 defaultExecFlags = ExecFlags {