got annexing working

Annex.hs

@@ -0,0 +1,36 @@
+{- git-annex
+ -}
+
+module Annex where
+
+import Backend
+import System.Posix.Files
+import System.Directory
+import GitRepo
+import Utility
+
+{- An annexed file's content is stored in .git/annex/. -}
+annexedFileLocation repo file = do
+	dir <- gitDir repo
+	return $ dir ++ "/annex/" ++ (gitRelative repo file)
+
+{- Annexes a file, storing it in a backend, and then moving it into
+ - the annex directory and setting up the symlink pointing to its
+ - content. -}
+annexFile :: [Backend] -> GitRepo -> FilePath -> IO ()
+annexFile backends repo file = do
+	alreadyannexed <- lookupBackend backends repo file
+	case (alreadyannexed) of
+		Just _ -> error $ "already annexed " ++ file
+		Nothing -> do
+			stored <- storeFile backends repo file
+			if (not stored)
+				then error $ "no backend could store " ++ file
+				else symlink
+	where
+		symlink = do
+			dest <- annexedFileLocation repo file
+			createDirectoryIfMissing True (parentDir dest)
+			renameFile file dest
+			createSymbolicLink dest file
+			gitAdd repo file