Update working tree files fully atomically

This avoids commit churn by the assistant when eg,
replacing a file with a symlink.

But, just as importantly, it prevents the working tree being left with a
deleted file if git-annex, or perhaps the whole system, crashes at the
wrong time.

(It also probably avoids confusing displays in file managers.)

Annex/Direct.hs

@@ -153,8 +153,7 @@ mergeDirectCleanup d oldsha newsha = do
  	 - Symlinks are replaced with their content, if it's available. -}
 	movein k f = do
 		l <- calcGitLink f k
-		replaceFile f $
-			makeAnnexLink l
+		replaceFile f $ makeAnnexLink l
 		toDirect k f
 	
 	{- Any new, modified, or renamed files were written to the temp
@@ -179,15 +178,14 @@ toDirectGen k f = do
 				{- Move content from annex to direct file. -}
 				updateInodeCache k loc
 				thawContent loc
-				replaceFile f $
-					liftIO . moveFile loc
+				replaceFile f $ liftIO . moveFile loc
 			, return Nothing
 			)
 		(loc':_) -> ifM (isNothing <$> getAnnexLinkTarget loc')
 			{- Another direct file has the content; copy it. -}
 			( return $ Just $
 				replaceFile f $
-					void . liftIO . copyFileExternal loc'
+					liftIO . void . copyFileExternal loc'
 			, return Nothing
 			)