use ByteString for git config

The parser and looking up config keys in the map should both be faster
due to using ByteString.

I had hoped this would speed up startup time, but any improvement to
that was too small to measure. Seems worth keeping though.

Note that the parser breaks up the ByteString, but a config map ends up
pointing to the config as read, which is retained in memory until every
value from it is no longer used. This can change memory usage
patterns marginally, but won't affect git-annex.

Git/Config.hs

@@ -1,13 +1,17 @@
 {- git repository configuration handling
  -
- - Copyright 2010-2012 Joey Hess <id@joeyh.name>
+ - Copyright 2010-2019 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module Git.Config where
 
 import qualified Data.Map as M
+import qualified Data.ByteString as S
+import qualified Data.ByteString.Char8 as S8
 import Data.Char
 
 import Common
@@ -18,15 +22,15 @@ import qualified Git.Construct
 import Utility.UserInfo
 
 {- Returns a single git config setting, or a default value if not set. -}
-get :: String -> String -> Repo -> String
+get :: S.ByteString -> S.ByteString -> Repo -> S.ByteString
 get key defaultValue repo = M.findWithDefault defaultValue key (config repo)
 
 {- Returns a list with each line of a multiline config setting. -}
-getList :: String -> Repo -> [String]
+getList :: S.ByteString -> Repo -> [S.ByteString]
 getList key repo = M.findWithDefault [] key (fullconfig repo)
 
 {- Returns a single git config setting, if set. -}
-getMaybe :: String -> Repo -> Maybe String
+getMaybe :: S.ByteString -> Repo -> Maybe S.ByteString
 getMaybe key repo = M.lookup key (config repo)
 
 {- Runs git config and populates a repo with its config.
@@ -79,14 +83,14 @@ global = do
 {- Reads git config from a handle and populates a repo with it. -}
 hRead :: Repo -> Handle -> IO Repo
 hRead repo h = do
-	val <- hGetContentsStrict h
+	val <- S.hGetContents h
 	store val repo
 
 {- Stores a git config into a Repo, returning the new version of the Repo.
  - The git config may be multiple lines, or a single line.
  - Config settings can be updated incrementally.
  -}
-store :: String -> Repo -> IO Repo
+store :: S.ByteString -> Repo -> IO Repo
 store s repo = do
 	let c = parse s
 	updateLocation $ repo
@@ -96,7 +100,7 @@ store s repo = do
 
 {- Stores a single config setting in a Repo, returning the new version of
  - the Repo. Config settings can be updated incrementally. -}
-store' :: String -> String -> Repo -> Repo
+store' :: S.ByteString -> S.ByteString -> Repo -> Repo
 store' k v repo = repo
 	{ config = M.singleton k v `M.union` config repo
 	, fullconfig = M.unionWith (++) (M.singleton k [v]) (fullconfig repo)
@@ -127,49 +131,63 @@ updateLocation' r l = do
 		Just d -> do
 			{- core.worktree is relative to the gitdir -}
 			top <- absPath $ gitdir l
-			return $ l { worktree = Just $ absPathFrom top d }
+			let p = absPathFrom top (fromRawFilePath d)
+			return $ l { worktree = Just p }
 	return $ r { location = l' }
 
 {- Parses git config --list or git config --null --list output into a
  - config map. -}
-parse :: String -> M.Map String [String]
-parse [] = M.empty
+parse :: S.ByteString -> M.Map S.ByteString [S.ByteString]
 parse s
-	-- --list output will have an = in the first line
-	| all ('=' `elem`) (take 1 ls) = sep '=' ls
+	| S.null s = M.empty
+	-- --list output will have a '=' in the first line
+	-- (The first line of --null --list output is the name of a key,
+	-- which is assumed to never contain '='.)
+	| S.elem eq firstline = sep eq $ S.split nl s
 	-- --null --list output separates keys from values with newlines
-	| otherwise = sep '\n' $ splitc '\0' s
+	| otherwise = sep nl $ S.split 0 s
   where
-	ls = lines s
-	sep c = M.fromListWith (++) . map (\(k,v) -> (k, [v])) .
-		map (separate (== c))
+	nl = fromIntegral (ord '\n')
+	eq = fromIntegral (ord '=')
+	firstline = S.takeWhile (/= nl) s
+
+	sep c = M.fromListWith (++)
+		. map (\(k,v) -> (k, [S.drop 1 v])) 
+		. map (S.break (== c))
 
 {- Checks if a string from git config is a true value. -}
 isTrue :: String -> Maybe Bool
-isTrue s
+isTrue = isTrue' . encodeBS'
+
+isTrue' :: S.ByteString -> Maybe Bool
+isTrue' s
 	| s' == "true" = Just True
 	| s' == "false" = Just False
 	| otherwise = Nothing
   where
-	s' = map toLower s
+	s' = S8.map toLower s
 
 boolConfig :: Bool -> String
 boolConfig True = "true"
 boolConfig False = "false"
 
-isBare :: Repo -> Bool
-isBare r = fromMaybe False $ isTrue =<< getMaybe coreBare r
+boolConfig' :: Bool -> S.ByteString
+boolConfig' True = "true"
+boolConfig' False = "false"
 
-coreBare :: String
+isBare :: Repo -> Bool
+isBare r = fromMaybe False $ isTrue' =<< getMaybe coreBare r
+
+coreBare :: S.ByteString
 coreBare = "core.bare"
 
 {- Runs a command to get the configuration of a repo,
  - and returns a repo populated with the configuration, as well as the raw
  - output of the command. -}
-fromPipe :: Repo -> String -> [CommandParam] -> IO (Either SomeException (Repo, String))
+fromPipe :: Repo -> String -> [CommandParam] -> IO (Either SomeException (Repo, S.ByteString))
 fromPipe r cmd params = try $
 	withHandle StdoutHandle createProcessSuccess p $ \h -> do
-		val <- hGetContentsStrict h
+		val <- S.hGetContents h
 		r' <- store val r
 		return (r', val)
   where
@@ -177,7 +195,7 @@ fromPipe r cmd params = try $
 
 {- Reads git config from a specified file and returns the repo populated
  - with the configuration. -}
-fromFile :: Repo -> FilePath -> IO (Either SomeException (Repo, String))
+fromFile :: Repo -> FilePath -> IO (Either SomeException (Repo, S.ByteString))
 fromFile r f = fromPipe r "git"
 	[ Param "config"
 	, Param "--file"
@@ -187,13 +205,13 @@ fromFile r f = fromPipe r "git"
 
 {- Changes a git config setting in the specified config file.
  - (Creates the file if it does not already exist.) -}
-changeFile :: FilePath -> String -> String -> IO Bool
+changeFile :: FilePath -> S.ByteString -> S.ByteString -> IO Bool
 changeFile f k v = boolSystem "git"
 	[ Param "config"
 	, Param "--file"
 	, File f
-	, Param k
-	, Param v
+	, Param (decodeBS' k)
+	, Param (decodeBS' v)
 	]
 
 {- Unsets a git config setting, in both the git repo,
@@ -202,10 +220,10 @@ changeFile f k v = boolSystem "git"
  - If unsetting the config fails, including in a read-only repo, or
  - when the config is not set, returns Nothing.
  -}
-unset :: String -> Repo -> IO (Maybe Repo)
+unset :: S.ByteString -> Repo -> IO (Maybe Repo)
 unset k r = ifM (Git.Command.runBool ps r)
 	( return $ Just $ r { config = M.delete k (config r) }
 	, return Nothing
 	)
   where
-	ps = [Param "config", Param "--unset-all", Param k]
+	ps = [Param "config", Param "--unset-all", Param (decodeBS' k)]