add timestamps to unused log files

This will be used in expiring old unused objects. The timestamp is when it
was first noticed it was unused.

Backwards compatability: It supports reading old format unused log files.
The old version of git-annex will ignore lines in log files written by the
new version, so the worst interop problem would be git annex dropunused not
knowing some numbers that git-annex unused reported.

Command/Unused.hs

@@ -92,7 +92,7 @@ check file msg a c = do
 	l <- a
 	let unusedlist = number c l
 	unless (null l) $ showLongNote $ msg unusedlist
-	writeUnusedLog file unusedlist
+	updateUnusedLog file $ M.fromList unusedlist
 	return $ c + length l
 
 number :: Int -> [a] -> [(Int, a)]
@@ -328,9 +328,9 @@ data UnusedMaps = UnusedMaps
 
 withUnusedMaps :: (UnusedMaps -> Int -> CommandStart) -> CommandSeek
 withUnusedMaps a params = do
-	unused <- readUnusedLog ""
-	unusedbad <- readUnusedLog "bad"
-	unusedtmp <- readUnusedLog "tmp"
+	unused <- readUnusedMap ""
+	unusedbad <- readUnusedMap "bad"
+	unusedtmp <- readUnusedMap "tmp"
 	let m = unused `M.union` unusedbad `M.union` unusedtmp
 	let unusedmaps = UnusedMaps unused unusedbad unusedtmp
 	seekActions $ return $ map (a unusedmaps) $

Logs/Unused.hs

@@ -1,32 +1,71 @@
 {- git-annex unused log file
  -
- - Copyright 2010,2012 Joey Hess <joey@kitenet.net>
+ - This file is stored locally in .git/annex/, not in the git-annex branch.
+ -
+ - The format: "int key timestamp"
+ -
+ - The int is a short, stable identifier that the user can use to
+ - refer to this key. (Equivilant to a filename.)
+ -
+ - The timestamp indicates when the key was first determined to be unused.
+ - Older versions of the log omit the timestamp.
+ -
+ - Copyright 2010-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
 module Logs.Unused (
 	UnusedMap,
-	writeUnusedLog,
+	updateUnusedLog,
 	readUnusedLog,
+	readUnusedMap,
 	unusedKeys,
 ) where
 
 import qualified Data.Map as M
+import Data.Time.Clock.POSIX
+import Data.Time
+import System.Locale
 
 import Common.Annex
 import Types.Key
 import Utility.Tmp
 
+-- everything that is stored in the unused log
+type UnusedLog = M.Map Key (Int, Maybe POSIXTime)
+
+-- used to look up unused keys specified by the user
 type UnusedMap = M.Map Int Key
 
-writeUnusedLog :: FilePath -> [(Int, Key)] -> Annex ()
+log2map :: UnusedLog -> UnusedMap
+log2map = M.fromList . map (\(k, (i, _t)) -> (i, k)) . M.toList
+
+map2log :: POSIXTime -> UnusedMap -> UnusedLog
+map2log t = M.fromList . map (\(i, k) -> (k, (i, Just t))) . M.toList
+
+{- Only keeps keys that are in the new log, but uses any timestamps
+ - those keys had in the old log. -}
+preserveTimestamps :: UnusedLog -> UnusedLog -> UnusedLog
+preserveTimestamps oldl newl = M.intersection (M.unionWith oldts oldl newl) newl
+  where
+	oldts _old@(_, ts) _new@(int, _) = (int, ts)
+
+updateUnusedLog :: FilePath -> UnusedMap -> Annex ()
+updateUnusedLog prefix m = do
+	oldl <- readUnusedLog prefix
+	newl <- preserveTimestamps oldl . flip map2log m <$> liftIO getPOSIXTime
+	writeUnusedLog prefix newl
+
+writeUnusedLog :: FilePath -> UnusedLog -> Annex ()
 writeUnusedLog prefix l = do
 	logfile <- fromRepo $ gitAnnexUnusedLog prefix
-	liftIO $ viaTmp writeFile logfile $
-		unlines $ map (\(n, k) -> show n ++ " " ++ key2file k) l
+	liftIO $ viaTmp writeFile logfile $ unlines $ map format $ M.toList l
+  where
+	format (k, (i, Just t)) = show i ++ " " ++ key2file k ++ " " ++ show t
+	format (k, (i, Nothing)) = show i ++ " " ++ key2file k
 
-readUnusedLog :: FilePath -> Annex UnusedMap
+readUnusedLog :: FilePath -> Annex UnusedLog
 readUnusedLog prefix = do
 	f <- fromRepo $ gitAnnexUnusedLog prefix
 	ifM (liftIO $ doesFileExist f)
@@ -35,11 +74,15 @@ readUnusedLog prefix = do
 		, return M.empty
 		)
   where
-	parse line = case (readish tag, file2key rest) of
-		(Just num, Just key) -> Just (num, key)
+	parse line = case (readish sint, file2key skey, utcTimeToPOSIXSeconds <$> parseTime defaultTimeLocale "%s%Qs" ts) of
+		(Just int, Just key, mtimestamp) -> Just (key, (int, mtimestamp))
 		_ -> Nothing
 	  where
-		(tag, rest) = separate (== ' ') line
+		(sint, rest) = separate (== ' ') line
+		(skey, ts) = separate (== ' ') rest
+
+readUnusedMap :: FilePath -> Annex UnusedMap
+readUnusedMap = log2map <$$> readUnusedLog
 
 unusedKeys :: Annex [Key]
-unusedKeys = M.elems <$> readUnusedLog ""
+unusedKeys = M.keys <$> readUnusedLog ""

Test.hs

@@ -683,7 +683,7 @@ test_unused env = intmpclonerepoInDirect env $ do
   where
 	checkunused expectedkeys desc = do
 		git_annex env "unused" [] @? "unused failed"
-		unusedmap <- annexeval $ Logs.Unused.readUnusedLog ""
+		unusedmap <- annexeval $ Logs.Unused.readUnusedMap ""
 		let unusedkeys = M.elems unusedmap
 		assertEqual ("unused keys differ " ++ desc)
 			(sort expectedkeys) (sort unusedkeys)