speed up git annex move --from

Avoid extra ssh to check if the remote has the key, just trust the location
log (and propigate error if it's wrong).

Quick exit when asked to move files that are not on the remote, so this is
now suitable to be used on a big directory.

Commands.hs

@@ -438,32 +438,27 @@ moveToCleanup remote key = do
  -}
 moveFromStart :: FilePath -> Annex (Maybe SubCmdPerform)
 moveFromStart file = isAnnexed file $ \(key, backend) -> do
-	return $ Just $ moveFromPerform file key
+	g <- Annex.gitRepo
+	remote <- Remotes.commandLineRemote
+	l <- Remotes.keyPossibilities key
+	if (elem remote l)
+		then return $ Just $ moveFromPerform file key
+		else return Nothing
 moveFromPerform :: FilePath -> Key -> Annex (Maybe SubCmdCleanup)
 moveFromPerform file key = do
-	-- checking the remote is expensive, so not done in the start step
 	remote <- Remotes.commandLineRemote
-	isthere <- Remotes.inAnnex remote key
 	ishere <- inAnnex key
-	case (ishere, isthere) of
-		(_, Left err) -> do
-			showNote $ show err
-			return Nothing
-		(_, Right False) -> do
-			showNote $ "not present in " ++ (Git.repoDescribe remote)
-			return Nothing
-		(False, Right True) -> do
+	if (ishere)
+		then return $ Just $ moveFromCleanup remote key
+		else do
 			-- copy content from remote
 			ok <- getViaTmp key (Remotes.copyFromRemote remote key)
 			if (ok)
 				then return $ Just $ moveFromCleanup remote key
 				else return Nothing -- fail
-		(True, Right True) -> do
-			-- the content is already here, just remove from remote
-			return $ Just $ moveFromCleanup remote key
 moveFromCleanup :: Git.Repo -> Key -> Annex Bool
 moveFromCleanup remote key = do
-	-- Force drop content from the remote.
+	showNote $ "dropping from " ++ (Git.repoDescribe remote) ++ "..."
 	Remotes.runCmd remote "git-annex" ["dropkey", "--quiet", "--force",
 		"--backend=" ++ (backendName key),
 		keyName key]