type based git config handling

Now there's a Config type, that's extracted from the git config at startup.
Note that laziness means that individual config values are only looked up
and parsed on demand, and so we get implicit memoization for all of them.
So this is not only prettier and more type safe, it optimises several
places that didn't have explicit memoization before. As well as getting rid
of the ugly explicit memoization code.

Not yet done for annex.<remote>.* configuration settings.

Config.hs

@@ -12,7 +12,6 @@ import qualified Git
 import qualified Git.Config
 import qualified Git.Command
 import qualified Annex
-import Utility.DataUnits
 
 type UnqualifiedConfigKey = String
 data ConfigKey = ConfigKey String
@@ -21,8 +20,7 @@ data ConfigKey = ConfigKey String
 setConfig :: ConfigKey -> String -> Annex ()
 setConfig (ConfigKey key) value = do
 	inRepo $ Git.Command.run "config" [Param key, Param value]
-	newg <- inRepo Git.Config.reRead
-	Annex.changeState $ \s -> s { Annex.repo = newg }
+	Annex.changeGitRepo =<< inRepo Git.Config.reRead
 
 {- Unsets a git config setting. (Leaves it in state currently.) -}
 unsetConfig :: ConfigKey -> Annex ()
@@ -93,49 +91,28 @@ repoSyncable :: Git.Repo -> Annex Bool
 repoSyncable r = fromMaybe True . Git.Config.isTrue
 	<$> getRemoteConfig r "sync" ""
 
-{- If a value is specified, it is used; otherwise the default is looked up
- - in git config. forcenumcopies overrides everything. -}
-getNumCopies :: Maybe Int -> Annex Int
-getNumCopies v = perhaps (use v) =<< Annex.getState Annex.forcenumcopies
-  where
-	use (Just n) = return n
-	use Nothing = perhaps (return 1) =<< 
-		readish <$> getConfig (annexConfig "numcopies") "1"
-	perhaps fallback = maybe fallback (return . id)
-
 {- Gets the trust level set for a remote in git config. -}
 getTrustLevel :: Git.Repo -> Annex (Maybe String)
 getTrustLevel r = fromRepo $ Git.Config.getMaybe key
   where
 	(ConfigKey key) = remoteConfig r "trustlevel"
 
-{- Gets annex.diskreserve setting. -}
-getDiskReserve :: Annex Integer
-getDiskReserve = fromMaybe megabyte . readSize dataUnits
-	<$> getConfig (annexConfig "diskreserve") ""
-  where
-	megabyte = 1000000
+getNumCopies :: Maybe Int -> Annex Int
+getNumCopies (Just v) = return v
+getNumCopies Nothing = annexNumCopies <$> Annex.getConfig
 
-{- Gets annex.direct setting, cached for speed. -}
 isDirect :: Annex Bool
-isDirect = maybe fromconfig return =<< Annex.getState Annex.direct
-  where
-	fromconfig = do
-		direct <- fromMaybe False . Git.Config.isTrue <$>
-			getConfig (annexConfig "direct") ""
-		Annex.changeState $ \s -> s { Annex.direct = Just direct }
-		return direct
+isDirect = annexDirect <$> Annex.getConfig
 
 setDirect :: Bool -> Annex ()
 setDirect b = do
-	setConfig (annexConfig "direct") (if b then "true" else "false")
-	Annex.changeState $ \s -> s { Annex.direct = Just b }
+	setConfig (annexConfig "direct") $ if b then "true" else "false"
+	Annex.changeConfig $ \c -> c { annexDirect = b }
 
-{- Gets annex.httpheaders or annex.httpheaders-command setting,
- - splitting it into lines. -}
+{- Gets the http headers to use. -}
 getHttpHeaders :: Annex [String]
 getHttpHeaders = do
-	cmd <- getConfig (annexConfig "http-headers-command") ""
-	if null cmd
-		then fromRepo $ Git.Config.getList "annex.http-headers"
-		else lines <$> liftIO (readProcess "sh" ["-c", cmd])
+	v <- annexHttpHeadersCommand <$> Annex.getConfig
+	case v of
+		Just cmd -> lines <$> liftIO (readProcess "sh" ["-c", cmd])
+		Nothing -> annexHttpHeaders <$> Annex.getConfig