add upgrade.log

The upgrade from V9 uses this to avoid an automatic upgrade until 1 year
after the V9 update. It can also be used in future such situations.

Sponsored-by: Dartmouth College's Datalad project

Logs/Upgrade.hs

@@ -0,0 +1,52 @@
+{- git-annex upgrade log
+ -
+ - This file is stored locally in .git/annex/, not in the git-annex branch.
+ -
+ - The format: "version timestamp"
+ -
+ - Copyright 2022 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU AGPL version 3 or higher.
+ -}
+
+module Logs.Upgrade (
+	writeUpgradeLog,
+	readUpgradeLog,
+	timeOfUpgrade,
+) where
+
+import Annex.Common
+import Utility.TimeStamp
+import Logs.File
+import Types.RepoVersion
+
+import Data.Time.Clock.POSIX
+
+writeUpgradeLog :: RepoVersion -> POSIXTime-> Annex ()
+writeUpgradeLog v t = do
+	logfile <- fromRepo gitAnnexUpgradeLog
+	appendLogFile logfile gitAnnexUpgradeLock $ encodeBL $
+		show (fromRepoVersion v) ++ " " ++ show t
+
+readUpgradeLog :: Annex [(RepoVersion, POSIXTime)]
+readUpgradeLog = do
+	logfile <- fromRawFilePath <$> fromRepo gitAnnexUpgradeLog
+	ifM (liftIO $ doesFileExist logfile)
+		( mapMaybe parse . lines
+			<$> liftIO (readFileStrict logfile)
+		, return []
+		)
+  where
+	parse line = case (readish sint, parsePOSIXTime ts) of
+		(Just v, Just t) -> Just (RepoVersion v, t)
+		_ -> Nothing
+	  where
+		(sint, ts) = separate (== ' ') line
+
+timeOfUpgrade :: RepoVersion -> Annex (Maybe POSIXTime)
+timeOfUpgrade want = do
+	l <- readUpgradeLog
+	return $ case filter (\(v, _) -> v == want) l of
+		[] -> Nothing
+		l' -> Just (minimum (map snd l'))
+