add handling of symlink addition events

And just like that, annexed files can be moved and copies around within
the tree, and are automatically fixed to point to the content, and staged
in git. Huzzah!

Delete still remains TODO, with its troublesome race during add..

Command/Watch.hs

@@ -7,15 +7,18 @@
 
 module Command.Watch where
 
+import CmdLine
 import Common.Annex
 import Command
-import qualified Annex
-import CmdLine
 import Utility.Inotify
-import Control.Exception as E
+import qualified Annex
 import qualified Command.Add as Add
 import qualified Git.Command
+import qualified Annex.Queue
+import qualified Backend
+import Annex.Content
 
+import Control.Exception as E
 import System.INotify
 
 def :: [Command]
@@ -55,16 +58,41 @@ run startstate a f = do
 			_ <- shutdown True
 			return ()
 
+{- Adding a file is the same as git-annex add.
+ - The git queue is immediately flushed, so the file is added to git
+ - now, rather than later (when it may have been already moved or deleted!) -}
 onAdd :: FilePath -> Annex ()
-onAdd file = void $ doCommand $ do
+onAdd file = do
+	void $ doCommand $ do
 		showStart "add" file
 		next $ Add.perform file
+	Annex.Queue.flush
 
+{- A symlink might be an arbitrary symlink, which is just added.
+ - Or, if it is a git-annex symlink, ensure it points to the content
+ - before adding it.
+ -}
 onAddSymlink :: FilePath -> Annex ()
-onAddSymlink link = liftIO $ print $ "add symlink " ++ link
+onAddSymlink file = go =<< Backend.lookupFile file
+	where
+		go Nothing = addlink
+		go (Just (key, _)) = do
+			link <- calcGitLink file key
+			ifM ((==) link <$> liftIO (readSymbolicLink file))
+				( addlink
+				, do
+					liftIO $ removeFile file
+					liftIO $ createSymbolicLink link file
+					addlink
+				)
+		addlink = inRepo $ Git.Command.run "add"
+			[Params "--force --", File file]
 
 onDel :: FilePath -> Annex ()
 onDel file = liftIO $ print $ "del " ++ file
 
+{- A directory has been deleted, so tell git to remove anything that
+   was inside it from its cache. -}
 onDelDir :: FilePath -> Annex ()
-onDelDir dir = inRepo $ Git.Command.run "rm" [Params "--quiet -r", File dir]
+onDelDir dir = inRepo $ Git.Command.run "rm"
+	[Params "--quiet -r --cached --", File dir]