git-annex/Backend.hs
Joey Hess 1cdf2b923d assistant: Make expensive transfer scan work fully in direct mode.
The expensive scan uses lookupFile, but in direct mode, that doesn't work
for files that are present. So the scan was not finding things that are
present that need to be uploaded. (It did find things not present that
needed to be downloaded.)

Now lookupFile also works in direct mode. Note that it still prefers
symlinks on disk to info committed to git, in direct mode. This is
necessary to make things like Assistant.Threads.Watcher.onAddSymlink
work correctly, when given a new symlink not yet checked into git (or
replacing a file checked into git).
2013-01-05 15:57:53 -04:00

124 lines
3.6 KiB
Haskell

{- git-annex key/value backends
-
- Copyright 2010 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Backend (
list,
orderedList,
genKey,
lookupFile,
chooseBackend,
lookupBackendName,
maybeLookupBackendName
) where
import System.Posix.Files
import Common.Annex
import qualified Annex
import Annex.CheckAttr
import Annex.CatFile
import Types.Key
import Types.KeySource
import qualified Types.Backend as B
import Config
-- When adding a new backend, import it here and add it to the list.
import qualified Backend.SHA
import qualified Backend.WORM
import qualified Backend.URL
list :: [Backend]
list = Backend.SHA.backends ++ Backend.WORM.backends ++ Backend.URL.backends
{- List of backends in the order to try them when storing a new key. -}
orderedList :: Annex [Backend]
orderedList = do
l <- Annex.getState Annex.backends -- list is cached here
if not $ null l
then return l
else do
f <- Annex.getState Annex.forcebackend
case f of
Just name | not (null name) ->
return [lookupBackendName name]
_ -> do
l' <- gen . annexBackends <$> Annex.getGitConfig
Annex.changeState $ \s -> s { Annex.backends = l' }
return l'
where
gen [] = list
gen l = map lookupBackendName l
{- Generates a key for a file, trying each backend in turn until one
- accepts it. -}
genKey :: KeySource -> Maybe Backend -> Annex (Maybe (Key, Backend))
genKey source trybackend = do
bs <- orderedList
let bs' = maybe bs (: bs) trybackend
genKey' bs' source
genKey' :: [Backend] -> KeySource -> Annex (Maybe (Key, Backend))
genKey' [] _ = return Nothing
genKey' (b:bs) source = do
r <- B.getKey b source
case r of
Nothing -> genKey' bs source
Just k -> return $ Just (makesane k, b)
where
-- keyNames should not contain newline characters.
makesane k = k { keyName = map fixbadchar (keyName k) }
fixbadchar c
| c == '\n' = '_'
| otherwise = c
{- Looks up the key and backend corresponding to an annexed file,
- by examining what the file symlinks to.
-
- In direct mode, there is often no symlink on disk, in which case
- the symlink is looked up in git instead. However, a real symlink
- on disk still takes precedence over what was committed to git in direct
- mode.
-}
lookupFile :: FilePath -> Annex (Maybe (Key, Backend))
lookupFile file = do
tl <- liftIO $ tryIO $ readSymbolicLink file
case tl of
Right l
| isLinkToAnnex l -> makekey l
| otherwise -> return Nothing
Left _ -> ifM isDirect
( maybe (return Nothing) makeret =<< catKeyFile file
, return Nothing
)
where
makekey l = maybe (return Nothing) makeret (fileKey $ takeFileName l)
makeret k = let bname = keyBackendName k in
case maybeLookupBackendName bname of
Just backend -> do
return $ Just (k, backend)
Nothing -> do
warning $
"skipping " ++ file ++
" (unknown backend " ++ bname ++ ")"
return Nothing
{- Looks up the backend that should be used for a file.
- That can be configured on a per-file basis in the gitattributes file. -}
chooseBackend :: FilePath -> Annex (Maybe Backend)
chooseBackend f = Annex.getState Annex.forcebackend >>= go
where
go Nothing = maybeLookupBackendName <$> checkAttr "annex.backend" f
go (Just _) = Just . Prelude.head <$> orderedList
{- Looks up a backend by name. May fail if unknown. -}
lookupBackendName :: String -> Backend
lookupBackendName s = fromMaybe unknown $ maybeLookupBackendName s
where
unknown = error $ "unknown backend " ++ s
maybeLookupBackendName :: String -> Maybe Backend
maybeLookupBackendName s = headMaybe matches
where
matches = filter (\b -> s == B.name b) list