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.

Types/Config.hs

@@ -0,0 +1,64 @@
+{- git-annex configuration
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Types.Config ( 
+	Config(..),
+	extractConfig,
+) where
+
+import Common
+import qualified Git
+import qualified Git.Config
+import Utility.DataUnits
+
+{- Main git-annex settings. Each setting corresponds to a git-config key
+ - such as annex.foo -}
+data Config = Config
+	{ annexNumCopies :: Int
+	, annexDiskReserve :: Integer
+	, annexDirect :: Bool
+	, annexBackends :: [String]
+	, annexQueueSize :: Maybe Int
+	, annexBloomCapacity :: Maybe Int
+	, annexBloomAccuracy :: Maybe Int
+	, annexSshCaching :: Maybe Bool
+	, annexAlwaysCommit :: Bool
+	, annexDelayAdd :: Maybe Int
+	, annexHttpHeaders :: [String]
+	, annexHttpHeadersCommand :: Maybe String
+	}
+
+extractConfig :: Git.Repo -> Config
+extractConfig r = Config
+	{ annexNumCopies = get "numcopies" 1
+	, annexDiskReserve = fromMaybe onemegabyte $
+		readSize dataUnits =<< getmaybe "diskreserve"
+	, annexDirect = getbool "direct" False
+	, annexBackends = fromMaybe [] $
+		words <$> getmaybe "backends"
+	, annexQueueSize = getmayberead "queuesize"
+	, annexBloomCapacity = getmayberead "bloomcapacity"
+	, annexBloomAccuracy = getmayberead "bloomaccuracy"
+	, annexSshCaching = getmaybebool "sshcaching"
+	, annexAlwaysCommit = getbool "alwayscommit" True
+	, annexDelayAdd = getmayberead "delayadd"
+	, annexHttpHeaders = getlist "http-headers"
+	, annexHttpHeadersCommand = getmaybe "http-headers-command"
+	}
+  where
+	get k def = fromMaybe def $ getmayberead k
+	getbool k def = fromMaybe def $ getmaybebool k
+	getmaybebool k = Git.Config.isTrue =<< getmaybe k
+	getmayberead k = readish =<< getmaybe k
+	getmaybe k = Git.Config.getMaybe (key k) r
+	getlist k = Git.Config.getList (key k) r
+	key k = "annex." ++ k
+			
+	onemegabyte = 1000000
+
+{- Per-remote git-annex settings. Each setting corresponds to a git-config
+ - key such as annex.<remote>.foo -}