diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
 dist/
+dist-newstyle/
 cabal-dev/
+.ghc.environment*
+cabal.project.local
diff --git a/Merge.hs b/Merge.hs
--- a/Merge.hs
+++ b/Merge.hs
@@ -6,6 +6,7 @@
 import Control.Monad
 import Control.Exception
 import qualified Data.ByteString.Lazy.Char8 as BL
+import qualified Data.ByteString.Builder as BL (stringUtf8, toLazyByteString)
 import Data.Function (on)
 import Data.Maybe
 import qualified Data.List as L
@@ -35,9 +36,10 @@
                         , setCurrentDirectory
                         , createDirectoryIfMissing
                         , doesFileExist
+                        , listDirectory
                         )
 import System.Process (system)
-import System.FilePath ((</>))
+import System.FilePath ((</>), isExtensionOf)
 import System.Exit
 
 import qualified Cabal2Ebuild as C2E
@@ -64,7 +66,6 @@
 {-
 Requested features:
   * Add files to git?
-  * Print diff with the next latest version?
 -}
 
 readPackageString :: [String]
@@ -153,9 +154,59 @@
   cat <- maybe (Portage.resolveCategory verbosity overlay norm_pkgName) return m_category
   mergeGenericPackageDescription verbosity overlayPath cat (CabalInstall.packageDescription selectedPkg) True users_cabal_flags
 
+  -- Maybe generate a diff
+  let pkgPath = overlayPath </> (Portage.unCategory cat) </> (Cabal.unPackageName norm_pkgName)
+      newPkgId = Portage.fromCabalPackageId cat cabal_pkgId
+  pkgDir <- listDirectory pkgPath
+  case getPreviousPackageId pkgDir newPkgId of
+    Just validPkg -> do info verbosity "Generating a diff..."
+                        diffEbuilds overlayPath validPkg newPkgId
+    _ -> info verbosity "Nothing to diff!"
+  
+-- | Call diff between two ebuilds.
+diffEbuilds :: FilePath -> Portage.PackageId -> Portage.PackageId -> IO ()
+diffEbuilds fp a b = do _ <- system $ "diff -u --color=auto "
+                             ++ fp </> Portage.packageIdToFilePath a ++ " "
+                             ++ fp </> Portage.packageIdToFilePath b
+                        exitSuccess
+
+-- | Maybe return a PackageId of the next highest version for a given
+--   package, relative to the provided PackageId of the new version.
+--   We achieve this by mapping Portage.filePathToPackageId over the
+--   provided package directory, whose contents are filtered for files
+--   with the '.ebuild' file extension
+getPreviousPackageId :: [FilePath] -- ^ list of ebuilds for given package
+                     -> Portage.PackageId -- ^ new PackageId
+                     -> Maybe Portage.PackageId -- ^ maybe PackageId of previous version
+getPreviousPackageId pkgDir newPkgId = do
+  let pkgIds = reverse 
+               . L.sortOn (Portage.pkgVersion)
+               . filter (<newPkgId)
+               $ Portage.filePathToPackageId newPkgId
+               <$> filter (\fp -> ".ebuild" `isExtensionOf` fp) pkgDir
+  case pkgIds of
+    x:_ -> Just x
+    _ -> Nothing
+
 first_just_of :: [Maybe a] -> Maybe a
 first_just_of = msum
 
+-- Gentoo allows underscore ('_') names in IUSE only for
+-- USE_EXPAND values. If it's not a user-specified rename mangle
+-- it into a hyphen ('-').
+mangle_iuse :: String -> String
+mangle_iuse = map f
+  where f '_' = '-'
+        f c   = c
+
+-- | Remove "with_" or "with-" from beginning of flag names.
+drop_with :: String -> String
+drop_with = \x ->
+  case splitAt 5 x of
+    ("with_", b) -> b
+    ("with-", b) -> b
+    _ -> x
+
 -- used to be FlagAssignment in Cabal but now it's an opaque type
 type CabalFlags = [(Cabal.FlagName, Bool)]
 
@@ -232,11 +283,10 @@
                                     , let f = Cabal.unFlagName cabal_f
                                     ]
 
-
       cfn_to_iuse :: String -> String
       cfn_to_iuse cfn =
           case lookup cfn cf_to_iuse_rename of
-              Nothing  -> cfn
+              Nothing  -> mangle_iuse . drop_with $ cfn
               Just ein -> ein
 
       -- key idea is to generate all possible list of flags
@@ -383,13 +433,11 @@
                        Just ucf -> (\e -> e { E.used_options  = E.used_options e ++ [("flags", ucf)] }))
                $ C2E.cabal2ebuild cat pkgDesc
 
-  mergeEbuild verbosity existing_meta pkgdir ebuild cabal_flag_descs
+  mergeEbuild verbosity existing_meta pkgdir ebuild active_flag_descs
   when fetch $ do
     let cabal_pkgId = Cabal.packageId pkgDesc
         norm_pkgName = Cabal.packageName (Portage.normalizeCabalPackageId cabal_pkgId)
-    fetchDigestAndCheck
-      verbosity
-      (overlayPath </> display cat </> display norm_pkgName)
+    fetchDigestAndCheck verbosity (overlayPath </> display cat </> display norm_pkgName)
 
 fetchDigestAndCheck :: Verbosity
                     -> FilePath -- ^ directory of ebuild
@@ -423,7 +471,7 @@
 
 -- | Generate a list of tuples containing Cabal flag names and descriptions
 metaFlags :: [Cabal.Flag] -> [(String, String)]
-metaFlags flags = zip (Cabal.unFlagName . Cabal.flagName <$> flags) (Cabal.flagDescription <$> flags)
+metaFlags flags = zip (mangle_iuse . drop_with . Cabal.unFlagName . Cabal.flagName <$> flags) (Cabal.flagDescription <$> flags)
 
 mergeEbuild :: Verbosity -> EM.EMeta -> FilePath -> E.EBuild -> [Cabal.Flag] -> IO ()
 mergeEbuild verbosity existing_meta pkgdir ebuild flags = do
@@ -432,7 +480,9 @@
       epath = edir </> elocal
       emeta = "metadata.xml"
       mpath = edir </> emeta
-      default_meta = BL.pack $ Portage.makeDefaultMetadata (E.long_desc ebuild) (metaFlags flags)
+      default_meta = BL.toLazyByteString . BL.stringUtf8
+                     $ Portage.makeDefaultMetadata (E.long_desc ebuild)
+                     $ metaFlags flags
   createDirectoryIfMissing True edir
   now <- TC.getCurrentTime
 
diff --git a/Portage/GHCCore.hs b/Portage/GHCCore.hs
--- a/Portage/GHCCore.hs
+++ b/Portage/GHCCore.hs
@@ -31,7 +31,7 @@
 -- It means that first ghc in this list is a minmum default.
 ghcs :: [(DC.CompilerInfo, InstalledPackageIndex)]
 ghcs = modern_ghcs
-    where modern_ghcs  = [ghc741, ghc742, ghc761, ghc762, ghc782, ghc7101, ghc7102, ghc801, ghc802, ghc821, ghc843, ghc861, ghc863]
+    where modern_ghcs  = [ghc741, ghc742, ghc761, ghc762, ghc782, ghc7101, ghc7102, ghc801, ghc802, ghc821, ghc843, ghc861, ghc863, ghc881]
 
 cabalFromGHC :: [Int] -> Maybe Cabal.Version
 cabalFromGHC ver = lookup ver table
@@ -47,6 +47,7 @@
           , ([8,2,1],  Cabal.mkVersion [2,0,0,2])
           , ([8,4,3],  Cabal.mkVersion [2,2,0,1])
           , ([8,6,1],  Cabal.mkVersion [2,4,0,1])
+          , ([8,8,1],  Cabal.mkVersion [3,0,0,0])
           ]
 
 platform :: Platform
@@ -116,6 +117,9 @@
 ghc nrs = DC.unknownCompilerInfo c_id DC.NoAbiTag
     where c_id = CompilerId GHC (mkVersion nrs)
 
+ghc881 :: (DC.CompilerInfo, InstalledPackageIndex)
+ghc881 = (ghc [8,8,1], mkIndex ghc881_pkgs)
+
 ghc863 :: (DC.CompilerInfo, InstalledPackageIndex)
 ghc863 = (ghc [8,6,3], mkIndex ghc863_pkgs)
 
@@ -159,6 +163,38 @@
 -- Source: http://haskell.org/haskellwiki/Libraries_released_with_GHC
 --         and our binary tarballs (package.conf.d.initial subdir)
 
+ghc881_pkgs :: [Cabal.PackageIdentifier]
+ghc881_pkgs =
+  [ p "array" [0,5,4,0]
+  , p "base" [4,13,0,0]
+  , p "binary" [0,8,7,0] -- used by libghc
+  , p "bytestring" [0,10,9,0]
+--  , p "Cabal" [3,0,0,0]  package is upgradeable
+  , p "containers" [0,6,2,1]
+  , p "deepseq" [1,4,4,0] -- used by time
+  , p "directory" [1,3,3,2]
+  , p "filepath" [1,4,2,1]
+  , p "ghc-boot" [8,8,1] 
+  , p "ghc-boot-th" [8,8,1] 
+  , p "ghc-compact" [0,1,0,0]
+  , p "ghc-prim" [0,5,3,0]
+  , p "ghci" [8,8,1]
+--  , p "haskeline" [0,7,4,3]  package is upgradeable
+  , p "hpc" [0,6,0,3] -- used by libghc
+  , p "integer-gmp" [1,0,2,0]
+  --  , p "mtl" [2,2,2]  package is upgradeable(?)
+  --  , p "parsec" [3,1,14,0]  package is upgradeable(?)
+  , p "pretty" [1,1,3,6]
+  , p "process" [1,6,5,1]
+  --  , p "stm" [2,5,0,0]  package is upgradeable(?)
+  , p "template-haskell" [2,15,0,0] -- used by libghc
+  -- , p "terminfo" [0,4,1,4]
+  -- , p "text" [1,2,4,0] dependency of Cabal library
+  , p "time" [1,9,3,0] -- used by unix, directory, hpc, ghc. unsafe to upgrade
+  , p "transformers" [0,5,6,2] -- used by libghc
+  , p "unix" [2,7,2,2]
+--  , p "xhtml" [3000,2,2,1]
+  ]
 
 ghc863_pkgs :: [Cabal.PackageIdentifier]
 ghc863_pkgs =
diff --git a/Portage/PackageId.hs b/Portage/PackageId.hs
--- a/Portage/PackageId.hs
+++ b/Portage/PackageId.hs
@@ -13,6 +13,7 @@
     parseFriendlyPackage,
     normalizeCabalPackageName,
     normalizeCabalPackageId,
+    filePathToPackageId,
     packageIdToFilePath,
     cabal_pn_to_PN
   ) where
@@ -31,7 +32,7 @@
 import qualified Data.Char as Char (isAlphaNum, isSpace, toLower)
 
 import Distribution.Text(display)
-import System.FilePath ( (</>) )
+import System.FilePath ((</>), dropExtension)
 
 #if MIN_VERSION_base(4,11,0)
 import Prelude hiding ((<>))
@@ -40,7 +41,7 @@
 newtype Category = Category { unCategory :: String }
   deriving (Eq, Ord, Show, Read)
 
-data PackageName = PackageName Category Cabal.PackageName
+data PackageName = PackageName { category :: Category, cabalPkgName :: Cabal.PackageName }
   deriving (Eq, Ord, Show, Read)
 
 data PackageId = PackageId { packageId :: PackageName, pkgVersion :: Portage.Version }
@@ -67,6 +68,26 @@
     a <-> b = a ++ '-':b
     a <.> b = a ++ '.':b
 
+-- | Attempt to generate a PackageId from a FilePath. If not, return
+-- the provided PackageId as-is.
+filePathToPackageId :: PackageId -> FilePath -> PackageId
+filePathToPackageId pkgId fp = do
+      -- take package name from provided FilePath
+  let pn = take (length
+                 $ Cabal.unPackageName . cabalPkgName . packageId
+                 $ pkgId) fp
+      -- drop .ebuild file extension
+      p = dropExtension fp
+      -- drop package name and the following dash
+      v = drop ((length pn) +1) p
+      c = unCategory . category . packageId $ pkgId
+      -- parse and extract version
+      parsed_v = case parseVersion v of
+                   Just (Just my_v) -> my_v
+                   _ -> pkgVersion pkgId
+  -- Construct PackageId
+  PackageId (mkPackageName c pn) parsed_v
+  
 mkPackageName :: String -> String -> PackageName
 mkPackageName cat package = PackageName (Category cat) (Cabal.mkPackageName package)
 
@@ -133,5 +154,19 @@
       return (Just v)
     return (mc, p, mv)
 
+-- | Parse a String in the form of a Portage version
+parseVersion :: FilePath -> Maybe (Maybe Portage.Version)
+parseVersion str =
+    case [ p | (p,s) <- Parse.readP_to_S parser str
+           , all Char.isSpace s ] of
+      [] -> Nothing
+      (x:_) -> Just x
+    where
+      parser = do
+        mv <- Parse.option Nothing $ do
+                 v <- parse
+                 return (Just v)
+        return mv
+    
 cabal_pn_to_PN :: Cabal.PackageName -> String
 cabal_pn_to_PN = map toLower . display
diff --git a/hackport.cabal b/hackport.cabal
--- a/hackport.cabal
+++ b/hackport.cabal
@@ -1,5 +1,5 @@
 Name:           hackport
-Version:        0.6
+Version:        0.6.1
 License:        GPL
 License-file:   LICENSE
 Author:         Henning Günther, Duncan Coutts, Lennart Kolmodin