Repository tuning parameters can now be passed when initializing a repository for the first time.

* init: Repository tuning parameters can now be passed when initializing a
  repository for the first time. For details, see
  http://git-annex.branchable.com/tuning/
* merge: Refuse to merge changes from a git-annex branch of a repo
  that has been tuned in incompatable ways.

Logs/Difference/Pure.hs

@@ -0,0 +1,26 @@
+{- git-annex difference log, pure functions
+ -
+ - Copyright 2015 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Logs.Difference.Pure (
+	allDifferences,
+	parseDifferencesLog,
+) where
+
+import Data.Monoid
+import qualified Data.Map as M
+
+import Common.Annex
+import Types.Difference
+import Logs.UUIDBased
+
+parseDifferencesLog :: String -> (M.Map UUID Differences)
+parseDifferencesLog = simpleMap 
+	. parseLog (Just . fromMaybe UnknownDifferences . readish)
+
+-- The sum of all recorded differences, across all UUIDs.
+allDifferences :: M.Map UUID Differences -> Differences
+allDifferences = mconcat . M.elems