convert transitions.log to attoparsec and bytestring-builder

Not likely to be any speed gain here, but this completes porting every
log file over.

And, it let me get rid of code copied from ghc and modified, so
simplifying the licensing.

Annex/Branch.hs

@@ -183,7 +183,7 @@ updateTo' pairs = do
 			else return $ "merging " ++
 				unwords (map Git.Ref.describe branches) ++ 
 				" into " ++ fromRef name
-		localtransitions <- parseTransitionsStrictly "local" . decodeBL
+		localtransitions <- parseTransitionsStrictly "local"
 			<$> getLocal transitionsLog
 		unless (null tomerge) $ do
 			showSideAction merge_desc
@@ -524,7 +524,7 @@ handleTransitions jl localts refs = do
 			return True
   where
 	getreftransition ref = do
-		ts <- parseTransitionsStrictly "remote" . decodeBL
+		ts <- parseTransitionsStrictly "remote"
 			<$> catFile ref transitionsLog
 		return (ref, ts)
 
@@ -560,7 +560,7 @@ performTransitionsLocked jl ts neednewlocalbranch transitionedrefs = do
 		| neednewlocalbranch && null transitionedrefs = "new branch for transition " ++ tdesc
 		| otherwise = "continuing transition " ++ tdesc
 	tdesc = show $ map describeTransition tlist
-	tlist = transitionList ts
+	tlist = knownTransitionList ts
 
 	{- The changes to make to the branch are calculated and applied to
 	 - the branch directly, rather than going through the journal,