support pointer files

Backend.lookupFile is changed to always fall back to catKey when
operating on a file that's not a symlink.

catKey is changed to understand pointer files, as well as annex symlinks.

Before, catKey needed a file mode witness, to be sure it was looking at a
symlink. That was complicated stuff. Now, it doesn't actually care if a
file in git is a symlink or not; in either case asking git for the content
of the file will get the pointer to the key.

This does mean that git-annex will treat a link
foo -> WORM--bar as a git-annex file, and also treats
a regular file containing annex/objects/WORM--bar as a git-annex file.

Calling catKey could make git-annex commands need to do more work than
before. This would especially be the case if a repo contained many regular
files, and only a few annexed files, as now git-annex will need to ask
git about the contents of the regular files.

9 files changed, 55 insertions, 82 deletions

diff --git a/Annex/AutoMerge.hs b/Annex/AutoMerge.hs
index bfbe71dc2..c32c3f66a 100644
--- a/Annex/AutoMerge.hs
+++ b/Annex/AutoMerge.hs
@@ -25,7 +25,6 @@ import qualified Git.Branch
 import Git.Types (BlobType(..))
 import Config
 import Annex.ReplaceFile
-import Git.FileMode
 import Annex.VariantFile
 
 import qualified Data.Set as S
@@ -135,7 +134,7 @@ resolveMerge' (Just us) them u = do
 		| select (LsFiles.unmergedBlobType u) == Just SymlinkBlob =
 			case select' (LsFiles.unmergedSha u) of
 				Nothing -> return Nothing
-				Just sha -> catKey sha symLinkMode
+				Just sha -> catKey sha
 		| otherwise = return Nothing
 	
 	makelink key = do
@@ -174,7 +173,7 @@ resolveMerge' (Just us) them u = do
 			case select' (LsFiles.unmergedSha u) of
 				Nothing -> noop
 				Just sha -> do
-					link <- catLink True sha
+					link <- catSymLinkTarget sha
 					replacewithlink item link
 		
 	resolveby a = do
diff --git a/Annex/CatFile.hs b/Annex/CatFile.hs
index 179149844..47ea86a31 100644
--- a/Annex/CatFile.hs
+++ b/Annex/CatFile.hs
@@ -1,6 +1,6 @@
 {- git cat-file interface, with handle automatically stored in the Annex monad
  -
- - Copyright 2011-2013 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2015 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -14,9 +14,10 @@ module Annex.CatFile (
 	catFileHandle,
 	catFileStop,
 	catKey,
+	parsePointer,
 	catKeyFile,
 	catKeyFileHEAD,
-	catLink,
+	catSymLinkTarget,
 ) where
 
 import qualified Data.ByteString.Lazy as L
@@ -29,8 +30,8 @@ import qualified Git.CatFile
 import qualified Annex
 import Git.Types
 import Git.FilePath
-import Git.FileMode
 import qualified Git.Ref
+import Types.Key
 
 catFile :: Git.Branch -> FilePath -> Annex L.ByteString
 catFile branch file = do
@@ -80,52 +81,36 @@ catFileStop = do
 		(s { Annex.catfilehandles = M.empty }, Annex.catfilehandles s)
 	liftIO $ mapM_ Git.CatFile.catFileStop (M.elems m)
 
-{- From the Sha or Ref of a symlink back to the key.
- -
- - Requires a mode witness, to guarantee that the file is a symlink.
- -}
-catKey :: Ref -> FileMode -> Annex (Maybe Key)
-catKey = catKey' True
+{- From ref to a symlink or a pointer file, get the key. -}
+catKey :: Ref -> Annex (Maybe Key)
+catKey ref = do
+	o <- catObject ref
+	if L.length o > maxsz
+		then return Nothing -- too big
+		else do
+			let l = decodeBS o
+			let l' = fromInternalGitPath l
+			return $ if isLinkToAnnex l'
+				then fileKey $ takeFileName l'
+				else parsePointer l
+  where
+	-- Want to avoid buffering really big files in git into memory.
+	-- 8192 bytes is plenty for a pointer to a key.
+	-- Pad some more to allow for any pointer files that might have
+	-- lines after the key explaining what the file is used for.
+	maxsz = 81920
 
-catKey' :: Bool -> Sha -> FileMode -> Annex (Maybe Key)
-catKey' modeguaranteed sha mode
-	| isSymLink mode = do
-		l <- catLink modeguaranteed sha
-		return $ if isLinkToAnnex l
-			then fileKey $ takeFileName l
-			else Nothing
-	| otherwise = return Nothing
+{- Only look at the first line of a pointer file. -}
+parsePointer :: String -> Maybe Key
+parsePointer s = headMaybe (lines s) >>= file2key
 
 {- Gets a symlink target. -}
-catLink :: Bool -> Sha -> Annex String
-catLink modeguaranteed sha = fromInternalGitPath . decodeBS <$> get
-  where
-	-- If the mode is not guaranteed to be correct, avoid
-	-- buffering the whole file content, which might be large.
-	-- 8192 is enough if it really is a symlink.
-	get
-		| modeguaranteed = catObject sha
-		| otherwise = L.take 8192 <$> catObject sha
-
-{- Looks up the key corresponding to the Ref using the running cat-file.
- -
- - Currently this always has to look in HEAD, because cat-file --batch
- - does not offer a way to specify that we want to look up a tree object
- - in the index. So if the index has a file staged not as a symlink,
- - and it is a symlink in head, the wrong mode is gotten.
- - Also, we have to assume the file is a symlink if it's not yet committed
- - to HEAD. For these reasons, modeguaranteed is not set.
- -}
-catKeyChecked :: Bool -> Ref -> Annex (Maybe Key)
-catKeyChecked needhead ref@(Ref r) =
-	catKey' False ref =<< findmode <$> catTree treeref
+catSymLinkTarget :: Sha -> Annex String
+catSymLinkTarget sha = fromInternalGitPath . decodeBS <$> get
   where
-	pathparts = split "/" r
-	dir = intercalate "/" $ take (length pathparts - 1) pathparts
-	file = fromMaybe "" $ lastMaybe pathparts
-	treeref = Ref $ if needhead then "HEAD" ++ dir ++ "/" else dir ++ "/"
-	findmode = fromMaybe symLinkMode . headMaybe .
-		 map snd . filter (\p -> fst p == file)
+	-- Avoid buffering the whole file content, which might be large.
+	-- 8192 is enough if it really is a symlink or pointer file.
+	get = L.take 8192 <$> catObject sha
 
 {- From a file in the repository back to the key.
  -
@@ -151,8 +136,8 @@ catKeyChecked needhead ref@(Ref r) =
 catKeyFile :: FilePath -> Annex (Maybe Key)
 catKeyFile f = ifM (Annex.getState Annex.daemon)
 	( catKeyFileHEAD f
-	, catKeyChecked True $ Git.Ref.fileRef f
+	, catKey $ Git.Ref.fileRef f
 	)
 
 catKeyFileHEAD :: FilePath -> Annex (Maybe Key)
-catKeyFileHEAD f = catKeyChecked False $ Git.Ref.fileFromRef Git.Ref.headRef f
+catKeyFileHEAD f = catKey $ Git.Ref.fileFromRef Git.Ref.headRef f
diff --git a/Annex/Direct.hs b/Annex/Direct.hs
index 495ff5e75..803f020ca 100644
--- a/Annex/Direct.hs
+++ b/Annex/Direct.hs
@@ -53,8 +53,8 @@ stageDirect = do
 	{- Determine what kind of modified or deleted file this is, as
 	 - efficiently as we can, by getting any key that's associated
 	 - with it in git, as well as its stat info. -}
-	go (file, Just sha, Just mode) = withTSDelta $ \delta -> do
-		shakey <- catKey sha mode
+	go (file, Just sha, Just _mode) = withTSDelta $ \delta -> do
+		shakey <- catKey sha
 		mstat <- liftIO $ catchMaybeIO $ getSymbolicLinkStatus file
 		mcache <- liftIO $ maybe (pure Nothing) (toInodeCache delta file) mstat
 		filekey <- isAnnexLink file
@@ -107,8 +107,8 @@ preCommitDirect = do
 		withkey (DiffTree.srcsha diff) (DiffTree.srcmode diff) removeAssociatedFile
 		withkey (DiffTree.dstsha diff) (DiffTree.dstmode diff) addAssociatedFile
 	  where
-		withkey sha mode a = when (sha /= nullSha) $ do
-			k <- catKey sha mode
+		withkey sha _mode a = when (sha /= nullSha) $ do
+			k <- catKey sha
 			case k of
 				Nothing -> noop
 				Just key -> void $ a key $
@@ -256,16 +256,16 @@ updateWorkTree d oldref force = do
 	makeabs <- flip fromTopFilePath <$> gitRepo
 	let fsitems = zip (map (makeabs . DiffTree.file) items) items
 	forM_ fsitems $
-		go makeabs DiffTree.srcsha DiffTree.srcmode moveout moveout_raw
+		go makeabs DiffTree.srcsha moveout moveout_raw
 	forM_ fsitems $
-		go makeabs DiffTree.dstsha DiffTree.dstmode movein movein_raw
+		go makeabs DiffTree.dstsha movein movein_raw
 	void $ liftIO cleanup
   where
-	go makeabs getsha getmode a araw (f, item)
+	go makeabs getsha a araw (f, item)
 		| getsha item == nullSha = noop
 		| otherwise = void $
 			tryNonAsync . maybe (araw item makeabs f) (\k -> void $ a item makeabs k f)
-				=<< catKey (getsha item) (getmode item)
+				=<< catKey (getsha item)
 
 	moveout _ _ = removeDirect
 
diff --git a/Annex/View.hs b/Annex/View.hs
index 2b8a80e5f..567522a54 100644
--- a/Annex/View.hs
+++ b/Annex/View.hs
@@ -413,13 +413,13 @@ withViewChanges addmeta removemeta = do
 	handleremovals item
 		| DiffTree.srcsha item /= nullSha =
 			handlechange item removemeta
-				=<< catKey (DiffTree.srcsha item) (DiffTree.srcmode item)
+				=<< catKey (DiffTree.srcsha item)
 		| otherwise = noop
 	handleadds makeabs item
 		| DiffTree.dstsha item /= nullSha = 
 			handlechange item addmeta
 				=<< ifM isDirect
-					( catKey (DiffTree.dstsha item) (DiffTree.dstmode item)
+					( catKey (DiffTree.dstsha item)
 					-- optimisation
 					, isAnnexLink $ makeabs $ DiffTree.file item
 					)
diff --git a/Backend.hs b/Backend.hs
index 922d0c2a7..28f83c7e0 100644
--- a/Backend.hs
+++ b/Backend.hs
@@ -26,7 +26,6 @@ import Annex.Link
 import Types.Key
 import Types.KeySource
 import qualified Types.Backend as B
-import Config
 
 -- When adding a new backend, import it here and add it to the list.
 import qualified Backend.Hash
@@ -81,22 +80,17 @@ genKey' (b:bs) source = do
 {- Looks up the key corresponding to an annexed file,
  - by examining what the file links to.
  -
- - In direct mode, there is often no link on disk, in which case
- - the symlink is looked up in git instead. However, a real link
- - on disk still takes precedence over what was committed to git in direct
- - mode.
+ - An unlocked file will not have a link on disk, so fall back to
+ - looking for a pointer to a key in git.
  -}
 lookupFile :: FilePath -> Annex (Maybe Key)
 lookupFile file = do
 	mkey <- isAnnexLink file
 	case mkey of
 		Just key -> makeret key
-		Nothing -> ifM isDirect
-			( maybe (return Nothing) makeret =<< catKeyFile file
-			, return Nothing
-			)
+		Nothing -> maybe (return Nothing) makeret =<< catKeyFile file
   where
-	makeret k = return $ Just k
+	makeret = return . Just
 
 getBackend :: FilePath -> Key -> Annex (Maybe Backend)
 getBackend file k = let bname = keyBackendName k in
diff --git a/CmdLine/Seek.hs b/CmdLine/Seek.hs
index 8d253e47d..0b6cc1e78 100644
--- a/CmdLine/Seek.hs
+++ b/CmdLine/Seek.hs
@@ -80,7 +80,7 @@ withFilesInRefs a = mapM_ go
 		l <- inRepo $ LsTree.lsTree (Git.Ref r)
 		forM_ l $ \i -> do
 			let f = getTopFilePath $ LsTree.file i
-			v <- catKey (Git.Ref $ LsTree.sha i) (LsTree.mode i)
+			v <- catKey (Git.Ref $ LsTree.sha i)
 			case v of
 				Nothing -> noop
 				Just k -> whenM (matcher $ MatchingKey k) $
diff --git a/Command/Indirect.hs b/Command/Indirect.hs
index c12c91a48..f5234b4dc 100644
--- a/Command/Indirect.hs
+++ b/Command/Indirect.hs
@@ -76,7 +76,7 @@ perform = do
 						return Nothing
 				| otherwise -> 
 					maybe noop (fromdirect f)
-						=<< catKey sha mode
+						=<< catKey sha
 			_ -> noop
 	go _ = noop
 
diff --git a/Command/Smudge.hs b/Command/Smudge.hs
index 6cca8035e..c2dc28540 100644
--- a/Command/Smudge.hs
+++ b/Command/Smudge.hs
@@ -11,6 +11,7 @@ import Common.Annex
 import Command
 import Types.Key
 import Annex.Content
+import Annex.CatFile
 import Annex.MetaData
 import Annex.FileMatcher
 import Types.KeySource
@@ -100,17 +101,11 @@ ingest file = do
 		=<< liftIO (getFileStatus file)
 	return k
 
+-- Could add a newline and some text explaining this file is a pointer.
+-- parsePointer only looks at the first line.
 emitPointer :: Key -> IO ()
 emitPointer = putStrLn . key2file
 
-parsePointer :: String -> Maybe Key
-parsePointer s
-	| length s' >= maxsz = Nothing -- too long to be a key pointer
-	| otherwise = headMaybe (lines s') >>= file2key
-  where
-	s' = take maxsz s
-	maxsz = 81920
-
 updateAssociatedFiles :: Key -> FilePath -> Annex ()
 updateAssociatedFiles k f = do
 	h <- AssociatedFiles.openDb
diff --git a/Command/Undo.hs b/Command/Undo.hs
index c647dfba4..0692dce34 100644
--- a/Command/Undo.hs
+++ b/Command/Undo.hs
@@ -72,7 +72,7 @@ perform p = do
 		f <- mkrel di
 		whenM isDirect $
 			maybe noop (`removeDirect` f)
-				=<< catKey (srcsha di) (srcmode di)
+				=<< catKey (srcsha di)
 		liftIO $ nukeFile f
 
 	forM_ adds $ \di -> do
@@ -80,6 +80,6 @@ perform p = do
 		inRepo $ Git.run [Param "checkout", Param "--", File f]
 		whenM isDirect $
 			maybe noop (`toDirect` f)
-				=<< catKey (dstsha di) (dstmode di)
+				=<< catKey (dstsha di)
 
 	next $ liftIO cleanup