Initial implementation of case splitting

- It doesn't handle vars correctly yet

src/GHCMod.hs

@@ -38,6 +38,7 @@ usage =    progVersion
         ++ "\t ghc-mod debug" ++ ghcOptHelp ++ "\n"
         ++ "\t ghc-mod info" ++ ghcOptHelp ++ "<HaskellFile> <module> <expression>\n"
         ++ "\t ghc-mod type" ++ ghcOptHelp ++ "<HaskellFile> <module> <line-no> <column-no>\n"
+        ++ "\t ghc-mod split" ++ ghcOptHelp ++ "<HaskellFile> <module> <line-no> <column-no>\n"
         ++ "\t ghc-mod find <symbol>\n"
         ++ "\t ghc-mod lint [-h opt] <HaskellFile>\n"
         ++ "\t ghc-mod root\n"
@@ -119,6 +120,7 @@ main = flip E.catches handlers $ do
       "debug"   -> debugInfo opt cradle
       "info"    -> nArgs 3 infoExpr opt cradle cmdArg1 cmdArg3
       "type"    -> nArgs 4 $ typeExpr opt cradle cmdArg1 (read cmdArg3) (read cmdArg4)
+      "split"   -> nArgs 4 $ splitVar opt cradle cmdArg1 (read cmdArg3) (read cmdArg4)
       "find"    -> runGhcMod opt $ nArgs 1 $ findSymbol cmdArg1
       "lint"    -> nArgs 1 withFile (lintSyntax opt) cmdArg1
       "root"    -> rootInfo opt cradle

src/GHCModi.hs

@@ -144,6 +144,7 @@ loop opt set mvar = do
         "lint"   -> toGhcMod $ lintStx  opt set arg
         "info"   -> toGhcMod $ showInfo opt set arg
         "type"   -> toGhcMod $ showType opt set arg
+        "split"  -> toGhcMod $ doSplit  opt set arg
         "boot"   -> bootIt set
         "browse" -> browseIt set arg
         "quit"   -> return ("quit", False, set)
@@ -254,6 +255,16 @@ showType opt set fileArg  = do
     ret <- types opt file (read line) (read column)
     return (ret, True, set')
 
+doSplit :: Options
+        -> Set FilePath
+        -> FilePath
+        -> Ghc (String, Bool, Set FilePath)
+doSplit opt set fileArg  = do
+    let [file, line, column] = words fileArg
+    set' <- newFileSet set file
+    ret <- splits opt file (read line) (read column)
+    return (ret, True, set')
+
 ----------------------------------------------------------------
 
 bootIt :: Set FilePath