optimisation: avoid stat call

This commit was sponsored by Paul Walmsley on Patreon.

Annex/Content.hs

@@ -583,17 +583,15 @@ linkAnnex fromto key src (Just srcic) dest destmode =
 				then Database.Keys.addInodeCaches key [srcic, destic]
 				else Database.Keys.addInodeCaches key [srcic]
 			return LinkAnnexNoop
-		Nothing -> ifM (linkOrCopy key src dest destmode)
-			( do
+		Nothing -> linkOrCopy key src dest destmode >>= \case
+			Nothing -> failed
+			Just r -> do
 				case fromto of
 					From -> thawContent dest
-					To -> do
-						s <- liftIO $ getFileStatus dest
-						unless (linkCount s > 1) $
-							freezeContent dest
+					To -> case r of
+						Copied -> freezeContent dest
+						Linked -> noop
 				checksrcunchanged
-			, failed
-			)
   where
 	failed = do
 		Database.Keys.addInodeCaches key [srcic]

Annex/Content/LowLevel.hs

@@ -29,6 +29,8 @@ secureErase file = maybe noop go =<< annexSecureEraseCommand <$> Annex.getGitCon
 		boolSystem "sh" [Param "-c", Param $ gencmd basecmd]
 	gencmd = massReplace [ ("%file", shellEscape file) ]
 
+data LinkedOrCopied = Linked | Copied
+
 {- Hard links or copies src to dest, which must not already exist.
  -
  - Only uses a hard link when annex.thin is enabled and when src is
@@ -42,13 +44,13 @@ secureErase file = maybe noop go =<< annexSecureEraseCommand <$> Annex.getGitCon
  - execute bit will be set. The mode is not fully copied over because
  - git doesn't support file modes beyond execute.
  -}
-linkOrCopy :: Key -> FilePath -> FilePath -> Maybe FileMode -> Annex Bool
+linkOrCopy :: Key -> FilePath -> FilePath -> Maybe FileMode -> Annex (Maybe LinkedOrCopied)
 linkOrCopy = linkOrCopy' (annexThin <$> Annex.getGitConfig)
 
-linkOrCopy' :: Annex Bool -> Key -> FilePath -> FilePath -> Maybe FileMode -> Annex Bool
+linkOrCopy' :: Annex Bool -> Key -> FilePath -> FilePath -> Maybe FileMode -> Annex (Maybe LinkedOrCopied)
 linkOrCopy' canhardlink key src dest destmode
 	| maybe False isExecutable destmode = copy =<< getstat
-	| otherwise = catchBoolIO $
+	| otherwise = catchDefaultIO Nothing $
 		ifM canhardlink
 			( hardlink
 			, copy =<< getstat
@@ -58,9 +60,12 @@ linkOrCopy' canhardlink key src dest destmode
 		s <- getstat
 		if linkCount s > 1
 			then copy s
-			else liftIO (createLink src dest >> preserveGitMode dest destmode >> return True)
+			else liftIO (createLink src dest >> preserveGitMode dest destmode >> return (Just Linked))
 				`catchIO` const (copy s)
-	copy = checkedCopyFile' key src dest destmode
+	copy s = ifM (checkedCopyFile' key src dest destmode s)
+		( return (Just Copied)
+		, return Nothing
+		)
 	getstat = liftIO $ getFileStatus src
 
 {- Checks disk space before copying. -}

Annex/Content/PointerFile.hs

@@ -32,10 +32,9 @@ populatePointerFile restage k obj f = go =<< liftIO (isPointerFile f)
 		destmode <- liftIO $ catchMaybeIO $ fileMode <$> getFileStatus f
 		liftIO $ nukeFile f
 		(ic, populated) <- replaceFile f $ \tmp -> do
-			ok <- linkOrCopy k obj tmp destmode
-			if ok
-				then thawContent tmp
-				else liftIO $ writePointerFile tmp k destmode
+			ok <- linkOrCopy k obj tmp destmode >>= \case
+				Just _ -> thawContent tmp >> return True
+				Nothing -> liftIO (writePointerFile tmp k destmode) >> return False
 			ic <- withTSDelta (liftIO . genInodeCache tmp)
 			return (ic, ok)
 		maybe noop (restagePointerFile restage f) ic

Command/ReKey.hs

@@ -85,7 +85,7 @@ linkKey file oldkey newkey = ifM (isJust <$> isAnnexLink file)
 	 - and vulnerable to corruption. -}
 	( getViaTmpFromDisk RetrievalAllKeysSecure DefaultVerify newkey $ \tmp -> unVerified $ do
 		oldobj <- calcRepo (gitAnnexLocation oldkey)
-		linkOrCopy' (return True) newkey oldobj tmp Nothing
+		isJust <$> linkOrCopy' (return True) newkey oldobj tmp Nothing
 	, do
 		ic <- withTSDelta (liftIO . genInodeCache file)
 	 	{- The file being rekeyed is itself an unlocked file, so if