converting more log files to use Builder

Probably not any particular speedup in this, since most of these logs
are not written to often. Possibly chunk log writing is sped up, but
writes to chunk logs are interleaved with expensive data transfers to
remotes, so unlikely to be a noticiable speedup.

Logs/MapLog.hs

@@ -1,12 +1,10 @@
-{-# LANGUAGE CPP #-}
-
 {- git-annex Map log
  -
  - This is used to store a Map, in a way that can be union merged.
  -
  - A line of the log will look like: "timestamp field value"
  -
- - Copyright 2014 Joey Hess <id@joeyh.name>
+ - Copyright 2014, 2019 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -22,6 +20,7 @@ import Annex.VectorClock
 import Logs.Line
 
 import qualified Data.Map.Strict as M
+import Data.ByteString.Builder
 
 data LogEntry v = LogEntry
 	{ changed :: VectorClock
@@ -30,13 +29,16 @@ data LogEntry v = LogEntry
 
 type MapLog f v = M.Map f (LogEntry v)
 
-showMapLog :: (f -> String) -> (v -> String) -> MapLog f v -> String
-showMapLog fieldshower valueshower = unlines . map showpair . M.toList
+buildMapLog :: (f -> Builder) -> (v -> Builder) -> MapLog f v -> Builder
+buildMapLog fieldbuilder valuebuilder = mconcat . map genline . M.toList
   where
-	showpair (f, LogEntry (VectorClock c) v) =
-		unwords [show c, fieldshower f, valueshower v]
-	showpair (f, LogEntry Unknown v) =
-		unwords ["0", fieldshower f, valueshower v]
+	genline (f, LogEntry c v) = 
+		buildVectorClock c <> sp 
+			<> fieldbuilder f <> sp 
+			<> valuebuilder v <> nl
+	sp = charUtf8 ' '
+	nl = charUtf8 '\n'
+
 
 parseMapLog :: Ord f => (String -> Maybe f) -> (String -> Maybe v) -> String -> MapLog f v
 parseMapLog fieldparser valueparser = M.fromListWith best . mapMaybe parse . splitLines