rework command dispatching for add and pre-commit

Both subcommands do two different operations on different sets of files, so
allowing a subcommand to perform a list of operations cleans things up.

Command/Lock.hs

@@ -9,23 +9,17 @@ module Command.Lock where
 
 import Control.Monad.State (liftIO)
 import System.Directory
-import System.Posix.Files
 
-import Types
 import Command
 import Messages
 import qualified Annex
 import qualified GitRepo as Git
 
 {- Undo unlock -}
-start :: SubCmdStartString
-start file = do
-	locked <- isLocked file
-	if locked
-		then return Nothing
-		else do
-			showStart "lock" file
-			return $ Just $ perform file
+start :: SubCmdStartBackendFile
+start (file, _) = do
+	showStart "lock" file
+	return $ Just $ perform file
 
 perform :: FilePath -> SubCmdPerform
 perform file = do
@@ -36,17 +30,3 @@ perform file = do
 	-- checkout the symlink
 	liftIO $ Git.run g ["checkout", "--", file]
 	return $ Just $ return True -- no cleanup needed
-
-{- Checks if a file is unlocked for edit. -}
-isLocked :: FilePath -> Annex Bool
-isLocked file = do
-	-- check if it's a symlink first, as that's cheapest
-	s <- liftIO $ getSymbolicLinkStatus file
-	if (isSymbolicLink s)
-		then return True -- Symlinked files are always locked.
-		else do
-			-- Not a symlink, so see if the type has changed,
-			-- if so it is presumed to have been unlocked.
-			g <- Annex.gitRepo
-			typechanged <- liftIO $ Git.typeChangedFiles g file
-			return $ not $ elem file typechanged