convert old uuid-based log parsers to attoparsec

This preserves the workaround for the old bug that caused NoUUID items
to be stored in the log, prefixing log lines with " ". It's now handled
implicitly, by using takeWhile1 (/= ' ') to get the uuid.

There is a behavior change from the old parser, which split the value
into words and then recombined it. That meant that "foo  bar" and "foo\tbar"
came out as "foo bar". That behavior was not documented, and seems
surprising; it meant that after a git-annex describe here "foo  bar",
you wouldn't get that same string back out when git-annex displayed repo
descriptions.

Otoh, some other parsers relied on the old behavior, and the attoparsec
rewrites had to deal with the issue themselves...

For group.log, there are some edge cases around the user providing a
group name with a leading or trailing space. The old parser would ignore
such excess whitespace. The new parser does too, because the alternative
is to refuse to parse something like " group1  group2 " due to excess
whitespace, which would be even more confusing behavior.

The only git-annex branch log file that is not converted to attoparsec
and bytestring-builder now is transitions.log.

Logs/UUIDBased.hs

@@ -14,7 +14,7 @@
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE OverloadedStrings, TupleSections #-}
 
 module Logs.UUIDBased (
 	Log,
@@ -39,9 +39,12 @@ import Annex.VectorClock
 import Logs.MapLog
 import Logs.Line
 
+import qualified Data.ByteString as S
 import qualified Data.ByteString.Lazy as L
 import qualified Data.Attoparsec.ByteString.Lazy as A
+import qualified Data.Attoparsec.ByteString.Char8 as A8
 import Data.ByteString.Builder
+import qualified Data.DList as D
 
 type Log v = MapLog UUID v
 
@@ -56,32 +59,28 @@ buildLog builder = mconcat . map genline . M.toList
 	sp = charUtf8 ' '
 	nl = charUtf8 '\n'
 
-parseLog :: (String -> Maybe a) -> String -> Log a
+parseLog :: A.Parser a -> L.ByteString -> Log a
 parseLog = parseLogWithUUID . const
 
-parseLogWithUUID :: (UUID -> String -> Maybe a) -> String -> Log a
-parseLogWithUUID parser = M.fromListWith best . mapMaybe parse . splitLines
+parseLogWithUUID :: (UUID -> A.Parser a) -> L.ByteString -> Log a
+parseLogWithUUID parser = fromMaybe M.empty . A.maybeResult
+	. A.parse (logParser parser)
+
+logParser :: (UUID -> A.Parser a) -> A.Parser (Log a)
+logParser parser = M.fromListWith best <$> parseLogLines go
   where
-	parse line
-		-- This is a workaround for a bug that caused
-		-- NoUUID items to be stored in the log.
-		-- It can be removed at any time; is just here to clean
-		-- up logs where that happened temporarily.
-		| " " `isPrefixOf` line = Nothing
-		| null ws = Nothing
-		| otherwise = parser u (unwords info) >>= makepair
-	  where
-		makepair v = Just (u, LogEntry ts v)
-		ws = words line
-		u = toUUID $ Prelude.head ws
-		t = Prelude.last ws
-		ts
-			| tskey `isPrefixOf` t = fromMaybe Unknown $
-				parseVectorClock $ drop 1 $ dropWhile (/= '=') t
-			| otherwise = Unknown
-		info
-			| ts == Unknown = drop 1 ws
-			| otherwise = drop 1 $ beginning ws
+	go = do
+		u <- toUUID <$> A8.takeWhile1 (/= ' ')
+		(dl, ts) <- accumval D.empty
+		v <- either fail return $ A.parseOnly (parser u <* A.endOfInput)
+			(S.intercalate " " $ D.toList dl)
+		return (u, LogEntry ts v)
+	accumval dl =
+		((dl,) <$> parsetimestamp)
+		<|> (A8.char ' ' *> (A8.takeWhile (/= ' ')) >>= accumval . D.snoc dl)
+	parsetimestamp = 
+		(A8.string " timestamp=" *> vectorClockParser <* A.endOfInput)
+		<|> (const Unknown <$> A.endOfInput)
 
 buildLogNew :: (v -> Builder) -> Log v -> Builder
 buildLogNew = buildMapLog buildUUID
@@ -94,6 +93,3 @@ changeLog = changeMapLog
 
 addLog :: UUID -> LogEntry v -> Log v -> Log v
 addLog = addMapLog
-
-tskey :: String
-tskey = "timestamp="