implement import --duplicate

The other two options are harder, due to needing to get the key for a file
before adding it.

Command/Import.hs

@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2012-2013 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -13,30 +13,66 @@ import Common.Annex
 import Command
 import qualified Annex
 import qualified Command.Add
+import qualified Option
+import Utility.CopyFile
 
 def :: [Command]
-def = [notBareRepo $ command "import" paramPaths seek
+def = [withOptions opts $ notBareRepo $ command "import" paramPaths seek
 	SectionCommon "move and add files from outside git working copy"]
 
-seek :: [CommandSeek]
-seek = [withPathContents start]
+opts :: [Option]
+opts =
+	[ duplicateOption
+	, deduplicateOption
+	, cleanDuplicatesOption
+	]
 
-start :: (FilePath, FilePath) -> CommandStart
-start (srcfile, destfile) =
+duplicateOption :: Option
+duplicateOption = Option.flag [] "duplicate" "do not delete outside files"
+
+deduplicateOption :: Option
+deduplicateOption = Option.flag [] "deduplicate" "do not add files whose content has been seen"
+
+cleanDuplicatesOption :: Option
+cleanDuplicatesOption = Option.flag [] "clean-duplicates" "delete outside duplicate files (import nothing)"
+
+data DuplicateMode = Default | Duplicate | DeDuplicate | CleanDuplicates
+	deriving (Eq)
+
+getDuplicateMode :: Annex DuplicateMode
+getDuplicateMode = gen
+	<$> getflag duplicateOption
+	<*> getflag deduplicateOption
+	<*> getflag cleanDuplicatesOption
+  where
+  	getflag = Annex.getFlag . Option.name
+  	gen False False False = Default
+	gen True False False = Duplicate
+	gen False True False = DeDuplicate
+	gen False False True = CleanDuplicates
+	gen _ _ _ = error "bad combination of --duplicate, --deduplicate, --clean-duplicates"
+
+seek :: [CommandSeek]
+seek = [withValue getDuplicateMode $ \mode -> withPathContents $ start mode]
+
+start :: DuplicateMode -> (FilePath, FilePath) -> CommandStart
+start mode (srcfile, destfile) =
 	ifM (liftIO $ isRegularFile <$> getSymbolicLinkStatus srcfile)
 		( do
 			showStart "import" destfile
-			next $ perform srcfile destfile
+			next $ perform mode srcfile destfile
 		, stop
 		)
 
-perform :: FilePath -> FilePath -> CommandPerform
-perform srcfile destfile = do
+perform :: DuplicateMode -> FilePath -> FilePath -> CommandPerform
+perform mode srcfile destfile = do
 	whenM (liftIO $ doesFileExist destfile) $
 		unlessM (Annex.getState Annex.force) $
 			error $ "not overwriting existing " ++ destfile ++
 				" (use --force to override)"
 
 	liftIO $ createDirectoryIfMissing True (parentDir destfile)
-	liftIO $ moveFile srcfile destfile
+	liftIO $ if mode == Duplicate
+		then void $ copyFileExternal srcfile destfile
+		else moveFile srcfile destfile
 	Command.Add.perform destfile