Allow invoking 'hc-pkg init' via D.S.Program.HcPkg.

Cabal/Distribution/Simple/Program/HcPkg.hs

@@ -10,6 +10,7 @@
 -- Currently only GHC and LHC have hc-pkg programs.
 
 module Distribution.Simple.Program.HcPkg (
+    init,
     register,
     reregister,
     unregister,
@@ -18,6 +19,7 @@ module Distribution.Simple.Program.HcPkg (
     dump,
 
     -- * Program invocations
+    initInvocation,
     registerInvocation,
     reregisterInvocation,
     unregisterInvocation,
@@ -26,6 +28,7 @@ module Distribution.Simple.Program.HcPkg (
     dumpInvocation,
   ) where
 
+import Prelude hiding (init)
 import Distribution.Package
          ( PackageId, InstalledPackageId(..) )
 import Distribution.InstalledPackageInfo
@@ -62,6 +65,15 @@ import System.FilePath as FilePath
 import qualified System.FilePath.Posix as FilePath.Posix
 
 
+-- | Call @hc-pkg@ to initialise a package database at the location {path}.
+--
+-- > hc-pkg init {path}
+--
+init :: Verbosity -> ConfiguredProgram -> FilePath -> IO ()
+init verbosity hcPkg path =
+  runProgramInvocation verbosity
+    (initInvocation hcPkg verbosity path)
+
 -- | Call @hc-pkg@ to register a package.
 --
 -- > hc-pkg register {filename | -} [--user | --global | --package-db]
@@ -228,6 +240,14 @@ setInstalledPackageId pkginfo = pkginfo
 -- The program invocations
 --
 
+initInvocation :: ConfiguredProgram
+               -> Verbosity -> FilePath -> ProgramInvocation
+initInvocation hcPkg verbosity path =
+    programInvocation hcPkg args
+  where
+    args = ["init", path]
+        ++ verbosityOpts hcPkg verbosity
+
 registerInvocation, reregisterInvocation
   :: ConfiguredProgram -> Verbosity -> PackageDBStack
   -> Either FilePath InstalledPackageInfo