honor core.sharedRepository settings in lockContent

The content file may not be owned by the user running git-annex, in which
case, setting the owner write bit was not enough to let lockContent
act on the file. However, with some core.sharedRepository configs, the file
should be writable by the user's group. So, the thing to do is to call
thawContent on it.

Annex/Content.hs

@@ -182,11 +182,11 @@ lockContent key a = do
 #ifndef mingw32_HOST_OS
 	{- Since content files are stored with the write bit disabled, have
 	 - to fiddle with permissions to open for an exclusive lock. -}
-	lock contentfile Nothing = trylock $ liftIO $
+	lock contentfile Nothing = trylock $ bracket_
-		withModifiedFileMode contentfile
+		(thawContent contentfile)
-			(`unionFileModes` ownerWriteMode) $
+		(freezeContent contentfile)
-			maybe alreadylocked return
+		(maybe alreadylocked return 
-				=<< tryLockExclusive Nothing contentfile
+			=<< liftIO (tryLockExclusive Nothing contentfile))
 	lock _ (Just lockfile) = trylock $ do
 		mode <- annexFileMode
 		maybe alreadylocked return 

Utility/FileMode.hs

@@ -22,15 +22,12 @@ import Utility.Exception
 
 {- Applies a conversion function to a file's mode. -}
 modifyFileMode :: FilePath -> (FileMode -> FileMode) -> IO ()
-modifyFileMode f convert = void $ modifyFileMode' f convert
+modifyFileMode f convert = do
-modifyFileMode' :: FilePath -> (FileMode -> FileMode) -> IO FileMode
-modifyFileMode' f convert = do
 	s <- getFileStatus f
 	let old = fileMode s
 	let new = convert old
 	when (new /= old) $
 		setFileMode f new
-	return old
 
 {- Adds the specified FileModes to the input mode, leaving the rest
  - unchanged. -}
@@ -41,14 +38,6 @@ addModes ms m = combineModes (m:ms)
 removeModes :: [FileMode] -> FileMode -> FileMode
 removeModes ms m = m `intersectFileModes` complement (combineModes ms)
 
-{- Runs an action after changing a file's mode, then restores the old mode. -}
-withModifiedFileMode :: FilePath -> (FileMode -> FileMode) -> IO a -> IO a
-withModifiedFileMode file convert a = bracket setup cleanup go
-  where
-	setup = modifyFileMode' file convert
-	cleanup oldmode = modifyFileMode file (const oldmode)
-	go _ = a
-
 writeModes :: [FileMode]
 writeModes = [ownerWriteMode, groupWriteMode, otherWriteMode]