remove Eq instance for InodeCache

There are two types of equality here, and which one is right varies,
so this forces me to consider and choose between them.

Based on this, I learned that the commit in git anex sync was
always doing a strong comparison, even when in a repository where
the inodes had changed. Fixed that.

Annex/Content/Direct.hs

@@ -13,6 +13,7 @@ module Annex.Content.Direct (
 	recordedInodeCache,
 	updateInodeCache,
 	writeInodeCache,
+	compareInodeCaches,
 	sameInodeCache,
 	sameFileStatus,
 	removeInodeCache,
@@ -146,7 +147,7 @@ sameFileStatus key status = do
 {- If the inodes have changed, only the size and mtime are compared. -}
 compareInodeCaches :: InodeCache -> InodeCache -> Annex Bool
 compareInodeCaches x y
-	| x == y = return True
+	| x `compareStrong` y = return True
 	| otherwise = ifM inodesChanged
 		( return $ compareWeak x y
 		, return False
@@ -167,7 +168,7 @@ inodesChanged = maybe calc return =<< Annex.getState Annex.inodeschanged
 			=<< fromRepo gitAnnexInodeSentinal
 		scached <- readInodeSentinalFile
 		let changed = case (scache, scached) of
-			(Just c1, Just c2) -> c1 /= c2
+			(Just c1, Just c2) -> not $ compareStrong c1 c2
 			_ -> True
 		Annex.changeState $ \s -> s { Annex.inodeschanged = Just changed }
 		return changed

Annex/Direct.hs

@@ -51,8 +51,10 @@ stageDirect = do
 				 - modified, so compare the cache to see if
 				 - it really was. -}
 				oldcache <- recordedInodeCache key
-				when (oldcache /= Just cache) $
+				case oldcache of
-					modifiedannexed file key cache
+					Nothing -> modifiedannexed file key cache
+					Just c -> unlessM (compareInodeCaches c cache) $
+						modifiedannexed file key cache
 			(Just key, Nothing, _) -> deletedannexed file key
 			(Nothing, Nothing, _) -> deletegit file
 			(_, Just _, _) -> addgit file

Command/Add.hs

@@ -109,11 +109,10 @@ ingest (Just source) = do
 	backend <- chooseBackend $ keyFilename source
 	k <- genKey source backend
 	cache <- liftIO $ genInodeCache $ contentLocation source
-	case inodeCache source of
+	case (cache, inodeCache source) of
-		Nothing -> go k cache
+		(_, Nothing) -> go k cache
-		Just c
+		(Just newc, Just c) | compareStrong c newc -> go k cache
-			| (Just c == cache) -> go k cache
+		_ -> failure
-			| otherwise -> failure
   where
 	go k cache = ifM isDirect ( godirect k cache , goindirect k cache )
 

Utility/InodeCache.hs

@@ -12,7 +12,11 @@ import System.Posix.Types
 import Utility.QuickCheck
 
 data InodeCache = InodeCache FileID FileOffset EpochTime
-	deriving (Eq, Show)
+	deriving (Show)
+
+compareStrong :: InodeCache -> InodeCache -> Bool
+compareStrong (InodeCache inode1 size1 mtime1) (InodeCache inode2 size2 mtime2) =
+	inode1 == inode2 && size1 == size2 && mtime1 == mtime2
 
 {- Weak comparison of the inode caches, comparing the size and mtime, but
  - not the actual inode.  Useful when inodes have changed, perhaps
@@ -54,4 +58,6 @@ instance Arbitrary InodeCache where
 		<*> arbitrary
 
 prop_read_show_inodecache :: InodeCache -> Bool
-prop_read_show_inodecache c = readInodeCache (showInodeCache c) == Just c
+prop_read_show_inodecache c = case readInodeCache (showInodeCache c) of
+	Nothing -> False
+	Just c' -> compareStrong c c'