Add option to specify cabal-dev sandbox explicitly.

CabalDev.hs

@@ -17,11 +17,19 @@ import Types
 modifyOptions :: Options -> IO Options
 modifyOptions opts = found ||> notFound
   where
-    found = addPath opts <$> findCabalDev
+    found = do
+        path <- findCabalDev (sandbox opts)
+        return $ addPath opts path
     notFound = return opts
 
-findCabalDev :: IO String
+findCabalDev :: Maybe String -> IO FilePath
-findCabalDev = getCurrentDirectory >>= searchIt . splitPath
+findCabalDev (Just path) = do
+    a <- doesDirectoryExist path
+    if a then
+        findConf path
+      else
+        findCabalDev Nothing
+findCabalDev Nothing = getCurrentDirectory >>= searchIt . splitPath
 
 addPath :: Options -> String -> Options
 addPath orig_opts path = do

GHCMod.hs

@@ -57,6 +57,9 @@ argspec = [ Option "l" ["tolisp"]
           , Option "o" ["operators"]
             (NoArg (\opts -> opts { operators = True }))
             "print operators, too"
+          , Option "s" ["sandbox"]
+            (ReqArg (\s opts -> opts { sandbox = Just s }) "path")
+            "specify cabal-dev sandbox (default 'cabal-dev`)"
           ]
 
 parseArgs :: [OptDescr (Options -> Options)] -> [String] -> (Options, [String])

Types.hs

@@ -10,6 +10,7 @@ data Options = Options {
   , ghcOpts      :: [String]
   , operators    :: Bool
   , expandSplice :: Bool
+  , sandbox      :: Maybe String
   }
 
 defaultOptions :: Options
@@ -19,6 +20,7 @@ defaultOptions = Options {
   , ghcOpts      = []
   , operators    = False
   , expandSplice = False
+  , sandbox      = Nothing
   }
 
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