diffdriver: Added --get option

Removed the dontCheck repoExists, because running it in a repo that has not
been initialized yet would update location log with nouuid. And I guess
it's ok for it to only support running in git-annex repos.

Command/DiffDriver.hs

@@ -11,15 +11,16 @@ import Command
 import Annex.Content
 import Annex.Link
 import Git.Types
+import qualified Command.Get
 
 cmd :: Command
-cmd = dontCheck repoExists $
-	command "diffdriver" SectionPlumbing 
-		"git diff driver"
-		("-- cmd --") (seek <$$> optParser)
+cmd = command "diffdriver" SectionPlumbing 
+	"git diff driver"
+	("-- cmd --") (seek <$$> optParser)
 
 data Options = Options
 	{ textDiff :: Bool
+	, getOption :: Bool
 	, restOptions :: CmdParams
 	}
 
@@ -29,16 +30,16 @@ optParser desc = Options
 		( long "text"
 		<> help "diff text files with diff(1)"
 		)
+	<*> switch
+		( long "get"
+		<> help "get file contents from remotes"
+		)
 	<*> cmdParams desc
 
 seek :: Options -> CommandSeek
-seek = commandAction . start
-
-start :: Options -> CommandStart
-start opts = do
+seek opts = do
 	let (req, differ) = parseReq opts
-	void $ liftIO . exitBool =<< liftIO . differ =<< fixupReq req
-	stop
+	void $ liftIO . exitBool =<< liftIO . differ =<< fixupReq req opts
 
 data Req 
 	= Req
@@ -99,22 +100,35 @@ parseReq opts
  -
  - In either case, adjust the Req to instead point to the actual
  - location of the annexed object (which may or may not be present).
+ -
+ - This also gets objects from remotes when the getOption is set.
  -}
-fixupReq :: Req -> Annex Req
-fixupReq req@(UnmergedReq {}) = return req
-fixupReq req@(Req {}) = 
+fixupReq :: Req -> Options -> Annex Req
+fixupReq req@(UnmergedReq {}) _ = return req
+fixupReq req@(Req {}) opts = 
 	check rOldFile rOldMode (\r f -> r { rOldFile = f }) req
 		>>= check rNewFile rNewMode (\r f -> r { rNewFile = f })
   where
 	check getfile getmode setfile r = case readTreeItemType (encodeBS (getmode r)) of
 		Just TreeSymlink -> do
 			v <- getAnnexLinkTarget' f False
-			maybe (return r) repoint (parseLinkTargetOrPointer =<< v)
-		_ -> maybe (return r) repoint =<< liftIO (isPointerFile f)
+			maybe (return r) go (parseLinkTargetOrPointer =<< v)
+		_ -> maybe (return r) go =<< liftIO (isPointerFile f)
 	  where
+		f = toRawFilePath (getfile r)
+	  	go k = do
+			when (getOption opts) $
+				unlessM (inAnnex k) $
+					commandAction $
+						starting "get" ai si $
+							Command.Get.perform k af
+			repoint k
+		  where
+			ai = OnlyActionOn k (ActionItemKey k)
+			si = SeekInput []
+			af = AssociatedFile (Just f)
 		repoint k = withObjectLoc k $
 			pure . setfile r . fromRawFilePath
-		f = toRawFilePath (getfile r)
 
 externalDiffer :: String -> [String] -> Differ
 externalDiffer c ps = \req -> boolSystem c (map Param ps ++ serializeReq req )