more completely solve catKey memory leak

Done using a mode witness, which ensures it's fixed everywhere.

Fixing catFileKey was a bear, because git cat-file does not provide a
nice way to query for the mode of a file and there is no other efficient
way to do it. Oh, for libgit2..

Note that I am looking at tree objects from HEAD, rather than the index.
Because I cat-file cannot show a tree object for the index.
So this fix is technically incomplete. The only cases where it matters
are:

1. A new large file has been directly staged in git, but not committed.
2. A file that was committed to HEAD as a symlink has been staged
   directly in the index.

This could be fixed a lot better using libgit2.

Annex/CatFile.hs

@@ -8,6 +8,7 @@
 module Annex.CatFile (
 	catFile,
 	catObject,
+	catTree,
 	catObjectDetails,
 	catFileHandle,
 	catKey,
@@ -17,6 +18,7 @@ module Annex.CatFile (
 
 import qualified Data.ByteString.Lazy as L
 import qualified Data.Map as M
+import System.PosixCompat.Types
 
 import Common.Annex
 import qualified Git
@@ -24,6 +26,7 @@ import qualified Git.CatFile
 import qualified Annex
 import Git.Types
 import Git.FilePath
+import Git.FileMode
 
 catFile :: Git.Branch -> FilePath -> Annex L.ByteString
 catFile branch file = do
@@ -35,6 +38,11 @@ catObject ref = do
 	h <- catFileHandle
 	liftIO $ Git.CatFile.catObject h ref
 
+catTree :: Git.Ref -> Annex [(FilePath, FileMode)]
+catTree ref = do
+	h <- catFileHandle
+	liftIO $ Git.CatFile.catTree h ref
+
 catObjectDetails :: Git.Ref -> Annex (Maybe (L.ByteString, Sha))
 catObjectDetails ref = do
 	h <- catFileHandle
@@ -55,13 +63,39 @@ catFileHandle = do
 			Annex.changeState $ \s -> s { Annex.catfilehandles = m' }
 			return h
 
-{- From the Sha or Ref of a symlink back to the key. -}
-catKey :: Ref -> Annex (Maybe Key)
-catKey ref = do
-	l <- fromInternalGitPath . encodeW8 . L.unpack <$> catObject ref
-	return $ if isLinkToAnnex l
-		then fileKey $ takeFileName l
-		else Nothing
+{- 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 ref mode
+	| isSymLink mode = do
+		l <- fromInternalGitPath . encodeW8 . L.unpack <$> catObject ref
+		return $ if isLinkToAnnex l
+			then fileKey $ takeFileName l
+			else Nothing
+	| otherwise = return Nothing
+
+{- Looks up the file mode 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 sylink in head, the wrong mode is gotten. This is a bug.
+ - Also, we have to assume the file is a symlink if it's not yet committed
+ - to HEAD.
+ -}
+catKeyChecked :: Bool -> Ref -> Annex (Maybe Key)
+catKeyChecked needhead ref@(Ref r) = 
+	catKey ref =<< findmode <$> catTree treeref
+  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)
 
 {- From a file in the repository back to the key.
  -
@@ -76,7 +110,8 @@ catKey ref = do
  -
  - For command-line git-annex use, that doesn't matter. It's perfectly
  - reasonable for things staged in the index after the currently running
- - git-annex process to not be noticed by it.
+ - git-annex process to not be noticed by it. However, we do want to see
+ - what's in the index, since it may have uncommitted changes not in HEAD>
  -
  - For the assistant, this is much more of a problem, since it commits
  - files and then needs to be able to immediately look up their keys.
@@ -89,8 +124,8 @@ catKey ref = do
 catKeyFile :: FilePath -> Annex (Maybe Key)
 catKeyFile f = ifM (Annex.getState Annex.daemon)
 	( catKeyFileHEAD f
-	, catKey $ Ref $ ":./" ++ f
+	, catKeyChecked True (Ref $ ":./" ++ f)
 	)
 
 catKeyFileHEAD :: FilePath -> Annex (Maybe Key)
-catKeyFileHEAD f = catKey $ Ref $ "HEAD:./" ++ f
+catKeyFileHEAD f = catKeyChecked False (Ref $ "HEAD:./" ++ f)

Annex/Direct.hs

@@ -14,7 +14,6 @@ import qualified Git.Merge
 import qualified Git.DiffTree as DiffTree
 import Git.Sha
 import Git.Types
-import Git.FileMode
 import Annex.CatFile
 import qualified Annex.Queue
 import Logs.Location
@@ -46,9 +45,7 @@ stageDirect = do
 	 - 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) = do
-		shakey <- if isSymLink mode
-			then catKey sha
-			else return Nothing
+		shakey <- catKey sha mode
 		mstat <- liftIO $ catchMaybeIO $ getSymbolicLinkStatus file
 		filekey <- isAnnexLink file
 		case (shakey, filekey, mstat, toInodeCache =<< mstat) of
@@ -149,10 +146,9 @@ mergeDirectCleanup d oldsha newsha = do
 	  where
 		go getsha getmode a araw
 			| getsha item == nullSha = noop
-			| isSymLink (getmode item) =
+			| otherwise =
 				maybe (araw f) (\k -> void $ a k f)
-					=<< catKey (getsha item)
-			| otherwise = araw f
+					=<< catKey (getsha item) (getmode item)
 		f = DiffTree.file item
 
 	moveout = removeDirect

Command/Indirect.hs

@@ -78,7 +78,7 @@ perform = do
 						return Nothing
 				| otherwise -> 
 					maybe noop (fromdirect f)
-						=<< catKey sha
+						=<< catKey sha mode
 			_ -> noop
 	go _ = noop
 

Command/PreCommit.hs

@@ -16,7 +16,6 @@ import qualified Git.Ref
 import Annex.CatFile
 import Annex.Content.Direct
 import Git.Sha
-import Git.FileMode
 
 def :: [Command]
 def = [command "pre-commit" paramPaths seek SectionPlumbing
@@ -48,8 +47,8 @@ startDirect _ = next $ do
 		withkey (Git.DiffTree.srcsha diff) (Git.DiffTree.srcmode diff) removeAssociatedFile
 		withkey (Git.DiffTree.dstsha diff) (Git.DiffTree.dstmode diff) addAssociatedFile
 	  where
-		withkey sha mode a = when (sha /= nullSha && isSymLink mode) $ do
-			k <- catKey sha
+		withkey sha mode a = when (sha /= nullSha) $ do
+			k <- catKey sha mode
 			case k of
 				Nothing -> noop
 				Just key -> void $ a key (Git.DiffTree.file diff)

Command/Sync.hs

@@ -29,6 +29,7 @@ import qualified Remote.Git
 import Types.Key
 import Config
 import Annex.ReplaceFile
+import Git.FileMode
 
 import Data.Hash.MD5
 
@@ -321,7 +322,7 @@ resolveMerge' u
 		case msha of
 			Nothing -> a Nothing
 			Just sha -> do
-				key <- catKey sha
+				key <- catKey sha symLinkMode
 				maybe (return False) (a . Just) key
 
 {- The filename to use when resolving a conflicted merge of a file,

Git/CatFile.hs

@@ -130,4 +130,4 @@ catTree h treeref = go <$> catObjectDetails h treeref
 	parsemodefile b = 
 		let (modestr, file) = separate (== ' ') (encodeW8 $ L.unpack b)
 		in (file, readmode modestr)
-	readmode = fst . Prelude.head . readOct
+	readmode = fst . fromMaybe (0, undefined) . headMaybe . readOct

Git/FileMode.hs

@@ -13,8 +13,11 @@ import Utility.FileMode
 
 import System.PosixCompat.Types
 
+symLinkMode :: FileMode
+symLinkMode = 40960
+
 {- Git uses a special file mode to indicate a symlink. This is the case
  - even on Windows, so we hard code the valuse here, rather than using
  - System.Posix.Files.symbolicLinkMode. -}
 isSymLink :: FileMode -> Bool
-isSymLink = checkMode 40960
+isSymLink = checkMode symLinkMode

debian/changelog

@@ -18,8 +18,8 @@ git-annex (4.20130912) UNRELEASED; urgency=low
     numcopies levels. (--fast avoids calculating these)
   * gcrypt: Ensure that signing key is set to one of the participants keys.
   * webapp: Show encryption information when editing a remote.
-  * sync, pre-commit, indirect: Avoid unnecessarily catting non-symlink
-    files from git, which can be so large it runs out of memory.
+  * Avoid unnecessarily catting non-symlink files from git, which can be
+    so large it runs out of memory.
 
  -- Joey Hess <joeyh@debian.org>  Thu, 12 Sep 2013 12:14:46 -0400
 

doc/bugs/Huge_annex_out_of_memory_on_switch_to_indirect_mode_and_status.mdwn

@@ -61,3 +61,9 @@ commit  git-annex: out of memory (requested 985661440 bytes)
 
 # End of transcript or log.
 """]]
+
+> [[fixed|done]]. However, if you saw this behavior,
+> you have large files checked directly into git. You may
+> want to examine your repository and use git filter-branch to clean
+> it up.
+> --[[Joey]] 

doc/bugs/Out_of_memory_error_in_fsck_whereis_find_and_status_cmds.mdwn

@@ -77,4 +77,8 @@ Any thoughts on how I can get git-annex (esp. fsck) to complete would be appreci
 Thanks
 Giovanni
 
-[[!tag moreinfo]]
+> [[fixed|done]]. However, if you saw this behavior,
+> you have large files checked directly into git. You may
+> want to examine your repository and use git filter-branch to clean
+> it up.
+> --[[Joey]]