rework Differences data type
Eliminated complexity and future proofed. The most important change is that all functions over Difference are now total; any Difference that can be expressed should be handled. Avoids needs for sanity checking of inputs, and version skew with the future. Also, the difference.log now serializes a [Difference], not a Differences. This saves space and keeps it simpler. Note that [Difference] might contain conflicting differences (eg, [Version5, Version6]. In this case, one of them needs to consistently win over the others, probably based on Ord.
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@ -9,123 +9,74 @@ module Types.Difference (
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Difference(..),
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Differences(..),
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getDifferences,
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sanityCheckDifferences,
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differenceConfigKey,
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differenceConfigVal,
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hasDifference,
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) where
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import Utility.PartialPrelude
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import qualified Git
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import qualified Git.Config
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import Data.List
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import Data.Maybe
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import Data.Monoid
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import Control.Applicative
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-- Describes differences from the v5 repository format.
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--
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-- The serilization is stored in difference.log, so avoid changes that
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-- The serialization is stored in difference.log, so avoid changes that
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-- would break compatability.
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--
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-- Not breaking comparability is why a list of Differences is used, rather
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-- Not breaking compatability is why a list of Differences is used, rather
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-- than a sum type. With a sum type, adding a new field for some future
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-- difference would serialize to a value that an older version could not
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-- parse, even if that new field was not used. With the Differences list,
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-- old versions can still parse it, unless the new Difference constructor
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-- is used.
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--
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-- The constructors intentionally do not have parameters; this is to
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-- ensure that any Difference that can be expressed is supported.
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-- So, a new repository version would be Version6, rather than Version Int.
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data Difference
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= Version Int
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| ObjectHashLower Bool
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| ObjectHashDirectories Int
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| BranchHashDirectories Int
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deriving (Show, Read, Ord)
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instance Eq Difference where
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Version a == Version b = a == b
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ObjectHashLower a == ObjectHashLower b = a == b
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ObjectHashDirectories a == ObjectHashDirectories b = a == b
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BranchHashDirectories a == BranchHashDirectories b = a == b
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_ == _ = False
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= ObjectHashLower
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| OneLevelObjectHash
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| OneLevelBranchHash
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deriving (Show, Read, Ord, Eq, Enum, Bounded)
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data Differences
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= Differences [Difference]
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| UnknownDifferences
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deriving (Show, Read, Ord)
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instance Eq Differences where
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Differences a == Differences b = simplify (defver:a) == simplify (defver:b)
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_ == _ = False
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Differences a == Differences b = canon a == canon b
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_ == _ = False -- UnknownDifferences cannot be equal
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instance Monoid Differences where
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mempty = Differences []
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mappend (Differences l1) (Differences l2) = Differences (simplify (l1 ++ l2))
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mappend (Differences l1) (Differences l2) = Differences (canon (l1 ++ l2))
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mappend _ _ = UnknownDifferences
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-- This is the default repository version that is assumed when no other one
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-- is given. Note that [] == [Version 5]
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defver :: Difference
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defver = Version 5
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-- Given [Version 6, Version 5], returns [Version 6]
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simplify :: [Difference] -> [Difference]
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simplify = go . sort
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where
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go [] = []
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go (d:[]) = [d]
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go (d1:d2:ds)
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| like d1 d2 = go (d2:ds)
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| otherwise = d1 : go (d2:ds)
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like (Version _) (Version _) = True
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like _ _ = False
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canon :: [Difference] -> [Difference]
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canon = nub . sort
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getDifferences :: Git.Repo -> Differences
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getDifferences r = checksane $ Differences $ catMaybes
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[ ObjectHashLower
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<$> getmaybebool (differenceConfigKey (ObjectHashLower undefined))
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, ObjectHashDirectories
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<$> getmayberead (differenceConfigKey (ObjectHashDirectories undefined))
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, BranchHashDirectories
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<$> getmayberead (differenceConfigKey (BranchHashDirectories undefined))
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]
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getDifferences r = Differences $ catMaybes $
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map getmaybe [minBound .. maxBound]
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where
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getmaybe k = Git.Config.getMaybe k r
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getmayberead k = readish =<< getmaybe k
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getmaybebool k = Git.Config.isTrue =<< getmaybe k
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checksane = either error id . sanityCheckDifferences
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getmaybe d = case Git.Config.isTrue =<< Git.Config.getMaybe (differenceConfigKey d) r of
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Just True -> Just d
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_ -> Nothing
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differenceConfigKey :: Difference -> String
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differenceConfigKey (Version _) = "annex.version"
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differenceConfigKey (ObjectHashLower _) = tunable "objecthashlower"
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differenceConfigKey (ObjectHashDirectories _) = tunable "objecthashdirectories"
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differenceConfigKey (BranchHashDirectories _) = tunable "branchhashdirectories"
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differenceConfigKey ObjectHashLower = tunable "objecthashlower"
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differenceConfigKey OneLevelObjectHash = tunable "objecthash1"
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differenceConfigKey OneLevelBranchHash = tunable "branchhash1"
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differenceConfigVal :: Difference -> String
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differenceConfigVal (Version v) = show v
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differenceConfigVal (ObjectHashLower b) = Git.Config.boolConfig b
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differenceConfigVal (ObjectHashDirectories n) = show n
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differenceConfigVal (BranchHashDirectories n) = show n
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differenceConfigVal _ = Git.Config.boolConfig True
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tunable :: String -> String
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tunable k = "annex.tune." ++ k
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sanityCheckDifferences :: Differences -> Either String Differences
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sanityCheckDifferences d@(Differences l)
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| null problems = Right d
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| otherwise = Left (intercalate "; " problems)
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where
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problems = catMaybes (map check l)
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check (ObjectHashDirectories n)
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| n == 1 || n == 2 = Nothing
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| otherwise = Just $ "Bad value for objecthashdirectories -- should be 1 or 2, not " ++ show n
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check (BranchHashDirectories n)
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| n == 1 || n == 2 = Nothing
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| otherwise = Just $ "Bad value for branhhashdirectories -- should be 1 or 2, not " ++ show n
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check _ = Nothing
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sanityCheckDifferences UnknownDifferences = Left "unknown differences detected; update git-annex"
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hasDifference :: (Difference -> Bool) -> Differences -> Bool
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hasDifference f (Differences l) = any f l
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hasDifference _ UnknownDifferences = False
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