git-annex/Annex/VariantFile.hs
Joey Hess 96aba8eff7
Revert "cache the serialization of a Key"
This reverts commit 4536c93bb2.

That broke Read/Show of a Key, and unfortunately Key is read in at least
one place; the GitAnnexDistribution data type.

It would be worth bringing this optimisation back, but it would need
either a custom Read/Show instance that preserves back-compat, or
wrapping Key in a data type that contains the serialization, or changing
how GitAnnexDistribution is serialized.

Also, the Eq instance would need to compare keys with and without a
cached seralization the same.
2019-01-16 16:21:59 -04:00

45 lines
1.4 KiB
Haskell

{- git-annex .variant files for automatic merge conflict resolution
-
- Copyright 2014 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Annex.VariantFile where
import Annex.Common
import Utility.Hash
import qualified Data.ByteString.Lazy as L
variantMarker :: String
variantMarker = ".variant-"
mkVariant :: FilePath -> String -> FilePath
mkVariant file variant = takeDirectory file
</> dropExtension (takeFileName file)
++ variantMarker ++ variant
++ takeExtension file
{- The filename to use when resolving a conflicted merge of a file,
- that points to a key.
-
- Something derived from the key needs to be included in the filename,
- but rather than exposing the whole key to the user, a very weak hash
- is used. There is a very real, although still unlikely, chance of
- conflicts using this hash.
-
- In the event that there is a conflict with the filename generated
- for some other key, that conflict will itself be handled by the
- conflicted merge resolution code. That case is detected, and the full
- key is used in the filename.
-}
variantFile :: FilePath -> Key -> FilePath
variantFile file key
| doubleconflict = mkVariant file (keyFile key)
| otherwise = mkVariant file (shortHash $ serializeKey' key)
where
doubleconflict = variantMarker `isInfixOf` file
shortHash :: L.ByteString -> String
shortHash = take 4 . show . md5