group, ungroup: New commands to indicate groups of repositories.

Logs/Group.hs

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+{- git-annex group log
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Logs.Group (
+	groupSet,
+	lookupGroups,
+	groupMap,
+) where
+
+import qualified Data.Map as M
+import qualified Data.Set as S
+import Data.Time.Clock.POSIX
+
+import Common.Annex
+import qualified Annex.Branch
+import qualified Annex
+import Logs.UUIDBased
+import Types.Group
+
+{- Filename of group.log. -}
+groupLog :: FilePath
+groupLog = "group.log"
+
+{- Returns the groups of a given repo UUID. -}
+lookupGroups :: UUID -> Annex (S.Set Group)
+lookupGroups u = (fromMaybe S.empty . M.lookup u) <$> groupMap
+
+{- Changes the groups for a uuid in the groupLog. -}
+groupSet :: UUID -> S.Set Group -> Annex ()
+groupSet uuid@(UUID _) groups = do
+	ts <- liftIO getPOSIXTime
+	Annex.Branch.change groupLog $
+		showLog (unwords . S.toList) . changeLog ts uuid groups . 
+			parseLog (Just . S.fromList . words)
+	Annex.changeState $ \s -> s { Annex.groupmap = Nothing }
+groupSet NoUUID _ = error "unknown UUID; cannot modify group"
+
+{- Read the groupLog into a map. The map is cached for speed. -}
+groupMap :: Annex GroupMap
+groupMap = do
+	cached <- Annex.getState Annex.groupmap
+	case cached of
+		Just m -> return m
+		Nothing -> do
+			m <- simpleMap . parseLog (Just . S.fromList . words) <$>
+				Annex.Branch.get groupLog
+			Annex.changeState $ \s -> s { Annex.groupmap = Just m }
+			return m