avoid using MonadFail in ParseDuration

There's no instance for Either String, so that makes it not as useful as
it could be, so instead just return an Either String.

CmdLine/GitAnnex/Options.hs

@@ -286,7 +286,7 @@ keyMatchingOptions' =
 		<> help "match files the repository wants to drop"
 		<> hidden
 		)
-	, globalSetter Limit.addAccessedWithin $ option (str >>= parseDuration)
+	, globalSetter Limit.addAccessedWithin $ option (eitherReader parseDuration)
 		( long "accessedwithin"
 		<> metavar paramTime
 		<> help "match files accessed within a time interval"
@@ -403,7 +403,7 @@ jobsOption =
 
 timeLimitOption :: [GlobalOption]
 timeLimitOption = 
-	[ globalSetter Limit.addTimeLimit $ option (str >>= parseDuration)
+	[ globalSetter Limit.addTimeLimit $ option (eitherReader parseDuration)
 		( long "time-limit" <> short 'T' <> metavar paramTime
 		<> help "stop after the specified amount of time"
 		<> hidden

Command/Assistant.hs

@@ -39,7 +39,7 @@ optParser _ = AssistantOptions
 		( long "autostart"
 		<> help "start in known repositories"
 		)
-	<*> optional (option (str >>= parseDuration)
+	<*> optional (option (eitherReader parseDuration)
 		( long "startdelay" <> metavar paramNumber
 		<> help "delay before running startup scan"
 		))

Command/Expire.hs

@@ -103,8 +103,8 @@ parseExpire ps = do
 			return (Just r, parsetime now t)
 	parsetime _ "never" = Nothing
 	parsetime now s = case parseDuration s of
-		Nothing -> giveup $ "bad expire time: " ++ s
-		Just d -> Just (now - durationToPOSIXTime d)
+		Right d -> Just (now - durationToPOSIXTime d)
+		Left e -> giveup $ "bad expire time: " ++ e
 
 parseActivity :: MonadFail m => String -> m Activity
 parseActivity s = case readish s of

Command/Fsck.hs

@@ -81,7 +81,7 @@ optParser desc = FsckOptions
 			( long "more" <> short 'm'
 			<> help "continue an incremental fsck"
 			)
-		<|> (ScheduleIncrementalO <$> option (str >>= parseDuration)
+		<|> (ScheduleIncrementalO <$> option (eitherReader parseDuration)
 			( long "incremental-schedule" <> metavar paramTime
 			<> help "schedule incremental fscking"
 			))

Types/GitConfig.hs

@@ -177,7 +177,7 @@ extractGitConfig configsource r = GitConfig
 	, annexFsckNudge = getbool (annexConfig "fscknudge") True
 	, annexAutoUpgrade = toAutoUpgrade $
 		getmaybe (annexConfig "autoupgrade")
-	, annexExpireUnused = maybe Nothing Just . parseDuration
+	, annexExpireUnused = either (const Nothing) Just . parseDuration
 		<$> getmaybe (annexConfig "expireunused")
 	, annexSecureEraseCommand = getmaybe (annexConfig "secure-erase-command")
 	, annexGenMetaData = getbool (annexConfig "genmetadata") False

Types/ScheduledActivity.hs

@@ -46,16 +46,15 @@ parseScheduledActivity :: String -> Either String ScheduledActivity
 parseScheduledActivity s = case words s of
 	("fsck":"self":d:rest) -> qualified $ ScheduledSelfFsck
 		<$> parseSchedule (unwords rest)
-		<*> getduration d
+		<*> parseDuration d
 	("fsck":u:d:rest) -> qualified $ ScheduledRemoteFsck
 		<$> pure (toUUID u)
 		<*> parseSchedule (unwords rest)
-		<*> getduration d
+		<*> parseDuration d
 	_ -> qualified $ Left "unknown activity"
   where
 	qualified (Left e) = Left $ e ++ " in \"" ++ s ++ "\""
 	qualified v = v
-	getduration d = maybe (Left $ "failed to parse duration \""++d++"\"") Right (parseDuration d)
 
 fromScheduledActivities :: [ScheduledActivity] -> String
 fromScheduledActivities = intercalate "; " . map fromScheduledActivity

Utility/HumanTime.hs

@@ -19,7 +19,6 @@ module Utility.HumanTime (
 import Utility.PartialPrelude
 import Utility.QuickCheck
 
-import Control.Monad.Fail as Fail (MonadFail(..))
 import qualified Data.Map as M
 import Data.Time.Clock
 import Data.Time.Clock.POSIX (POSIXTime)
@@ -45,8 +44,8 @@ daysToDuration :: Integer -> Duration
 daysToDuration i = Duration $ i * dsecs
 
 {- Parses a human-input time duration, of the form "5h", "1m", "5h1m", etc -}
-parseDuration :: MonadFail m => String -> m Duration
-parseDuration = maybe parsefail (return . Duration) . go 0
+parseDuration :: String -> Either String Duration
+parseDuration d = maybe parsefail (Right . Duration) $ go 0 d
   where
 	go n [] = return n
 	go n s = do
@@ -56,7 +55,7 @@ parseDuration = maybe parsefail (return . Duration) . go 0
 				u <- M.lookup c unitmap
 				go (n + num * u) rest
 			_ -> return $ n + num
-	parsefail = Fail.fail "duration parse error; expected eg \"5m\" or \"1h5m\""
+	parsefail = Left $ "failed to parse duration \"" ++ d ++ "\" (expected eg \"5m\" or \"1h5m\")"
 
 fromDuration :: Duration -> String
 fromDuration Duration { durationSeconds = d }
@@ -102,4 +101,4 @@ instance Arbitrary Duration where
 	arbitrary = Duration <$> nonNegative arbitrary
 
 prop_duration_roundtrips :: Duration -> Bool
-prop_duration_roundtrips d = parseDuration (fromDuration d) == Just d
+prop_duration_roundtrips d = parseDuration (fromDuration d) == Right d