in which I discover void

void :: Functor f => f a -> f () -- ah, of course that's useful :)

Annex/Branch.hs

@@ -65,9 +65,7 @@ siblingBranches = inRepo $ Git.Ref.matchingUniq name
 
 {- Creates the branch, if it does not already exist. -}
 create :: Annex ()
-create = do
-	_ <- getBranch
-	return ()
+create = void $ getBranch
 
 {- Returns the ref of the branch, creating it first if necessary. -}
 getBranch :: Annex Git.Ref
@@ -325,10 +323,9 @@ setUnCommitted = do
 	liftIO $ writeFile file "1"
 
 setCommitted :: Annex ()
-setCommitted = do
+setCommitted = void $ do
 	file <- fromRepo gitAnnexIndexDirty
-	_ <- liftIO $ tryIO $ removeFile file
-	return ()
+	liftIO $ tryIO $ removeFile file
 
 {- Stages the journal into the index. -}
 stageJournal :: Annex ()

Annex/Ssh.hs

@@ -87,20 +87,17 @@ sshCleanup = do
 		stopssh socketfile = do
 			let (host, port) = socket2hostport socketfile
 			(_, params) <- sshInfo (host, port)
-			_ <- liftIO $ do
+			void $ liftIO $ do
 				-- "ssh -O stop" is noisy on stderr even with -q
 				let cmd = unwords $ toCommand $
 					[ Params "-O stop"
 					] ++ params ++ [Param host]
-				_ <- boolSystem "sh"
+				boolSystem "sh"
 					[ Param "-c"
 					, Param $ "ssh " ++ cmd ++ " >/dev/null 2>/dev/null"
 					]
-				--try $ removeFile socketfile
-				return ()
-			-- Cannot remove the lock file; other processes may
-			-- be waiting on our exclusive lock to use it.
-			return ()
+				-- Cannot remove the lock file; other processes may
+				-- be waiting on our exclusive lock to use it.
 
 hostport2socket :: String -> Maybe Integer -> FilePath
 hostport2socket host Nothing = host

Remote/Git.hs

@@ -313,7 +313,7 @@ commitOnCleanup r a = go `after` a
 		cleanup
 			| not $ Git.repoIsUrl r = liftIO $ onLocal r $
 				Annex.Branch.commit "update"
-			| otherwise = do
+			| otherwise = void $ do
 				Just (shellcmd, shellparams) <-
 					git_annex_shell r "commit" []
 				-- Throw away stderr, since the remote may not
@@ -322,6 +322,4 @@ commitOnCleanup r a = go `after` a
 				let cmd = shellcmd ++ " "
 					++ unwords (map shellEscape $ toCommand shellparams)
 					++ ">/dev/null 2>/dev/null"
-				_ <- liftIO $
-					boolSystem "sh" [Param "-c", Param cmd]
-				return ()
+				liftIO $ boolSystem "sh" [Param "-c", Param cmd]

Remote/Helper/Hooks.hs

@@ -47,9 +47,8 @@ runHooks r starthook stophook a = do
 	where
 		remoteid = show (uuid r)
 		run Nothing = return ()
-		run (Just command) = liftIO $ do
-			_ <- boolSystem "sh" [Param "-c", Param command]
-			return ()
+		run (Just command) = void $ liftIO $
+			boolSystem "sh" [Param "-c", Param command]
 		firstrun lck = do
 			-- Take a shared lock; This indicates that git-annex
 			-- is using the remote, and prevents other instances

Utility/FileMode.hs

@@ -15,9 +15,7 @@ import Foreign (complement)
 
 {- Applies a conversion function to a file's mode. -}
 modifyFileMode :: FilePath -> (FileMode -> FileMode) -> IO ()
-modifyFileMode f convert = do
-	_ <- modifyFileMode' f convert
-	return ()
+modifyFileMode f convert = void $ modifyFileMode' f convert
 modifyFileMode' :: FilePath -> (FileMode -> FileMode) -> IO FileMode
 modifyFileMode' f convert = do
 	s <- getFileStatus f

Utility/Inotify.hs

@@ -53,10 +53,9 @@ watchDir i test add del dir = watchDir' False i test add del dir
 watchDir' :: Bool -> INotify -> (FilePath -> Bool) -> Maybe (FilePath -> IO ()) -> Maybe (FilePath -> IO ()) -> FilePath -> IO ()
 watchDir' scan i test add del dir = do
 	if test dir
-		then do
+		then void $ do
 			_ <- addWatch i watchevents dir go
-			_ <- mapM walk =<< dirContents dir
-			return ()
+			mapM walk =<< dirContents dir
 		else return ()
 	where
 		watchevents
@@ -92,6 +91,5 @@ waitForTermination = do
 		check keyboardSignal mv
 	takeMVar mv
 	where
-		check sig mv = do
-			_ <- installHandler sig (CatchOnce $ putMVar mv ()) Nothing
-			return ()
+		check sig mv = void $
+			installHandler sig (CatchOnce $ putMVar mv ()) Nothing