more standard names for whenM and unlessM operators

These are defined in ifelse, but it's not currently available and I don't
want to pull in a library for 6 lines of code anyhow.

Also, ifelse sets the fixity to 1, which does not allow >>? error $ ...

Remote/Bup.hs

@@ -75,7 +75,7 @@ bupSetup u c = do
 	-- bup init will create the repository.
 	-- (If the repository already exists, bup init again appears safe.)
 	showNote "bup init"
-	bup "init" buprepo [] <|> error "bup init failed"
+	bup "init" buprepo [] >>! error "bup init failed"
 
 	storeBupUUID u buprepo
 
@@ -173,7 +173,7 @@ storeBupUUID u buprepo = do
 			showNote "storing uuid"
 			onBupRemote r boolSystem "git"
 				[Params $ "config annex.uuid " ++ u]
-				<|> error "ssh failed"
+					>>! error "ssh failed"
 		else liftIO $ do
 			r' <- Git.configRead r
 			let olduuid = Git.configGet r' "annex.uuid" ""

Remote/Directory.hs

@@ -63,7 +63,7 @@ directorySetup u c = do
 	let dir = maybe (error "Specify directory=") id $
 		M.lookup "directory" c
 	liftIO $ doesDirectoryExist dir
-		<|> error $ "Directory does not exist: " ++ dir
+		>>! error $ "Directory does not exist: " ++ dir
 	c' <- encryptionSetup c
 
 	-- The directory is stored in git config, not in this remote's

Remote/Rsync.hs

@@ -169,7 +169,7 @@ withRsyncScratchDir a = do
 	return res
 	where
 		nuke d = liftIO $ 
-			doesDirectoryExist d <&> removeDirectoryRecursive d
+			doesDirectoryExist d >>? removeDirectoryRecursive d
 
 rsyncRemote :: RsyncOpts -> [CommandParam] -> Annex Bool
 rsyncRemote o params = do