Fix space leak in fsck and drop commands.

The space leak was somehow caused by this line:

	absfiles <- mapM absPath files

I confess, I don't quite understand why this caused bad buffering,
but apparently the whole pipeline from git-ls-files backed up at that
point.

Happily, rewriting the code to only get the cwd once and use a pure
function to calculate absfiles clears it up, and should be a little more
efficient in syscalls too.

Command.hs

@@ -132,8 +132,7 @@ withAttrFilesInGit :: String -> CommandSeekAttrFiles
 withAttrFilesInGit attr a params = do
 	repo <- Annex.gitRepo
 	files <- liftIO $ runPreserveOrder (Git.inRepo repo) params
-	files' <- filterFiles files
-	liftM (map a) $ liftIO $ Git.checkAttr repo attr files'
+	liftM (map a) $ liftIO $ Git.checkAttr repo attr files
 withBackendFilesInGit :: CommandSeekBackendFiles
 withBackendFilesInGit a params = do
 	repo <- Annex.gitRepo

GitRepo.hs

@@ -449,9 +449,9 @@ checkAttr repo attr files = do
 	-- top of the repo). But we're passed files relative to the current
 	-- directory. Convert to absolute, and then convert the filenames
 	-- in its output back to relative.
-	absfiles <- mapM absPath files
-	(_, s) <- pipeBoth "git" (toCommand params) $ join "\0" absfiles
 	cwd <- getCurrentDirectory
+	let absfiles = map  (absPathFrom cwd) files
+	(_, s) <- pipeBoth "git" (toCommand params) $ join "\0" absfiles
 	return $ map (topair $ cwd++"/") $ lines s
 	where
 		params = gitCommandLine repo [Param "check-attr", Param attr, Params "-z --stdin"]

Utility.hs

@@ -12,6 +12,7 @@ module Utility (
 	readFileStrict,
 	parentDir,
 	absPath,
+	absPathFrom,
 	relPathCwdToDir,
 	relPathDirToDir,
 	boolSystem,
@@ -165,8 +166,14 @@ dirContains a b = a == b || a' == b' || (a'++"/") `isPrefixOf` b'
 absPath :: FilePath -> IO FilePath
 absPath file = do
 	cwd <- getCurrentDirectory
+	return $ absPathFrom cwd file
+
+{- Converts a filename into a normalized, absolute path
+ - from the specified cwd. -}
+absPathFrom :: FilePath -> FilePath -> FilePath
+absPathFrom cwd file =
 	case absNormPath cwd file of
-		Just f -> return f
+		Just f -> f
 		Nothing -> error $ "unable to normalize " ++ file
 
 {- Constructs a relative path from the CWD to a directory.

debian/changelog

@@ -12,6 +12,7 @@ git-annex (0.20110321) UNRELEASED; urgency=low
   * fsck: In fast mode, avoid checking checksums.
   * unused: In fast mode, just show all existing temp files as unused,
     and avoid expensive scan for other unused content.
+  * Fix space leak in fsck and drop commands.
 
  -- Joey Hess <joeyh@debian.org>  Tue, 22 Mar 2011 16:52:00 -0400