convert git-annex branch access to ByteStrings and Builders

Most of the individual logs are not converted yet, only presense logs
have an efficient ByteString Builder implemented so far. The rest
convert to and from String.

Logs/MetaData.hs

@@ -110,9 +110,9 @@ addMetaDataClocked' getlogfile k d@(MetaData m) c
 	| otherwise = do
 		config <- Annex.getGitConfig
 		Annex.Branch.change (getlogfile config k) $
-			showLog . simplifyLog 
+			encodeBL . showLog . simplifyLog 
 				. S.insert (LogEntry c metadata)
-				. parseLog
+				. parseLog . decodeBL
   where
 	metadata = MetaData $ M.filterWithKey (\f _ -> not (isLastChangedField f)) m
 
@@ -145,8 +145,8 @@ copyMetaData oldkey newkey
 			else do
 				config <- Annex.getGitConfig
 				Annex.Branch.change (metaDataLogFile config newkey) $
-					const $ showLog l
+					const $ encodeBL $ showLog l
 				return True
 
 readLog :: FilePath -> Annex (Log MetaData)
-readLog = parseLog <$$> Annex.Branch.get
+readLog = parseLog . decodeBL <$$> Annex.Branch.get