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.

Annex/VectorClock.hs

@@ -3,7 +3,7 @@
  - We don't have a way yet to keep true distributed vector clocks.
  - The next best thing is a timestamp.
  -
- - Copyright 2017 Joey Hess <id@joeyh.name>
+ - Copyright 2017-2019 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -11,12 +11,14 @@
 module Annex.VectorClock where
 
 import Data.Time.Clock.POSIX
+import Data.ByteString.Builder
 import Control.Applicative
 import Prelude
 
 import Utility.Env
 import Utility.TimeStamp
 import Utility.QuickCheck
+import Utility.FileSystemEncoding
 import qualified Data.Attoparsec.ByteString.Lazy as A
 
 -- | Some very old logs did not have any time stamp at all;
@@ -40,9 +42,12 @@ currentVectorClock = go =<< getEnv "GIT_ANNEX_VECTOR_CLOCK"
 		Nothing -> VectorClock <$> getPOSIXTime
 
 formatVectorClock :: VectorClock -> String
-formatVectorClock  Unknown = "0"
+formatVectorClock Unknown = "0"
 formatVectorClock (VectorClock t) = show t
 
+buildVectorClock :: VectorClock -> Builder
+buildVectorClock = byteString . encodeBS' . formatVectorClock
+
 parseVectorClock :: String -> Maybe VectorClock
 parseVectorClock t = VectorClock <$> parsePOSIXTime t