git-annex/Backend/URL.hs
Joey Hess e7652b0997
implement URL to VURL migration
This needs the content to be present in order to hash it. But it's not
possible for a module used by Backend.URL to call inAnnex because that
would entail a dependency loop. So instead, rely on the fact that
Command.Migrate calls inAnnex before performing a migration.

But, Command.ExamineKey calls fastMigrate and the key may or may not
exist, and it's not wanting to actually perform a migration in any case.
To handle that, had to add an additional value to fastMigrate to
indicate whether the content is inAnnex.

Factored generateEquivilantKey out of Remote.Web.

Note that migrateFromURLToVURL hardcodes use of the SHA256E backend.
It would have been difficult not to, given all the dependency loop
issues. But --backend and annex.backend are used to tell git-annex
migrate to use VURL in any case, so there's no config knob that
the user could expect to configure that.

Sponsored-by: Brock Spratlen on Patreon
2024-03-01 16:42:02 -04:00

43 lines
1.1 KiB
Haskell

{- git-annex URL backend -- keys whose content is available from urls.
-
- Copyright 2011-2024 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Backend.URL (
backends,
fromUrl
) where
import Annex.Common
import Types.Key
import Types.Backend
import Backend.Utilities
import Backend.VURL.Utilities (migrateFromURLToVURL)
backends :: [Backend]
backends = [backendURL]
backendURL :: Backend
backendURL = Backend
{ backendVariety = URLKey
, genKey = Nothing
, verifyKeyContent = Nothing
, verifyKeyContentIncrementally = Nothing
, canUpgradeKey = Nothing
, fastMigrate = Just migrateFromURLToVURL
-- The content of an url can change at any time, so URL keys are
-- not stable.
, isStableKey = const False
, isCryptographicallySecure = False
, isCryptographicallySecureKey = const (pure False)
}
{- Every unique url has a corresponding key. -}
fromUrl :: String -> Maybe Integer -> Bool -> Key
fromUrl url size verifiable = mkKey $ \k -> k
{ keyName = genKeyName url
, keyVariety = if verifiable then VURLKey else URLKey
, keySize = size
}