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/Presence.hs

@@ -31,8 +31,8 @@ import Git.Types (RefDate)
 {- Adds a LogLine to the log, removing any LogLines that are obsoleted by
  - adding it. -}
 addLog :: FilePath -> LogLine -> Annex ()
-addLog file line = Annex.Branch.change file $ \s ->
-	showLog $ compactLog (line : parseLog s)
+addLog file line = Annex.Branch.change file $ \b ->
+	buildLog $ compactLog (line : parseLog b)
 
 {- When a LogLine already exists with the same status and info, but an
  - older timestamp, that LogLine is preserved, rather than updating the log
@@ -41,7 +41,7 @@ addLog file line = Annex.Branch.change file $ \s ->
 maybeAddLog :: FilePath -> LogLine -> Annex ()
 maybeAddLog file line = Annex.Branch.maybeChange file $ \s -> do
 	m <- insertNewStatus line $ logMap $ parseLog s
-	return $ showLog $ mapLog m
+	return $ buildLog $ mapLog m
 
 {- Reads a log file.
  - Note that the LogLines returned may be in any order. -}
@@ -49,13 +49,13 @@ readLog :: FilePath -> Annex [LogLine]
 readLog = parseLog <$$> Annex.Branch.get
 
 {- Generates a new LogLine with the current time. -}
-logNow :: LogStatus -> String -> Annex LogLine
+logNow :: LogStatus -> LogInfo -> Annex LogLine
 logNow s i = do
 	c <- liftIO currentVectorClock
 	return $ LogLine c s i
 
 {- Reads a log and returns only the info that is still in effect. -}
-currentLogInfo :: FilePath -> Annex [String]
+currentLogInfo :: FilePath -> Annex [LogInfo]
 currentLogInfo file = map info <$> currentLog file
 
 currentLog :: FilePath -> Annex [LogLine]
@@ -66,6 +66,6 @@ currentLog file = filterPresent <$> readLog file
  -
  - The date is formatted as shown in gitrevisions man page.
  -}
-historicalLogInfo :: RefDate -> FilePath -> Annex [String]
+historicalLogInfo :: RefDate -> FilePath -> Annex [LogInfo]
 historicalLogInfo refdate file = map info . filterPresent . parseLog
 	<$> Annex.Branch.getHistorical refdate file