started borg special remote

Still need to implement 3 methods, but importKeyM looks like it will
work well to find annex object files.

Annex/Import.hs

@@ -455,7 +455,7 @@ importKeys remote importtreeconfig importcontent ignorelargefilesconfig importab
 			-- downloaded, which is a more expensive
 			-- operation generally.
 			let p' = if importcontent then nullMeterUpdate else p
-			importkey loc cid p' >>= \case
+			importkey loc cid sz p' >>= \case
 				Nothing -> return Nothing
 				Just unsizedk -> do
 					-- This avoids every remote needing

Remote/Borg.hs

@@ -5,11 +5,14 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module Remote.Borg (remote) where
 
 import Annex.Common
 import Types.Remote
 import Types.Creds
+import Types.Import
 import qualified Git
 import Config
 import Config.Cost
@@ -18,7 +21,10 @@ import Remote.Helper.Special
 import Remote.Helper.ExportImport
 import Annex.UUID
 import Types.ProposedAccepted
+import Crypto (isEncKey)
+import Utility.Metered
 
+import qualified System.FilePath.ByteString as P
 import qualified Data.Map as M
 
 type BorgRepo = String
@@ -62,7 +68,17 @@ gen r u rc gc rs = do
 		, checkPresent = checkPresentDummy
 		, checkPresentCheap = borgLocal borgrepo
 		, exportActions = exportUnsupported
-		, importActions = importUnsupported
+		, importActions = ImportActions
+			{ listImportableContents = listImportableContentsM borgrepo
+			, importKey = Just importKeyM
+			, retrieveExportWithContentIdentifier = retrieveExportWithContentIdentifierM borgrepo
+			, checkPresentExportWithContentIdentifier = checkPresentExportWithContentIdentifierM borgrepo
+			-- This remote is thirdPartyPopulated, so these
+			-- actions will never be used.
+			, storeExportWithContentIdentifier = storeExportWithContentIdentifier importUnsupported
+			, removeExportDirectoryWhenEmpty = removeExportDirectoryWhenEmpty importUnsupported
+			, removeExportWithContentIdentifier = removeExportWithContentIdentifier importUnsupported
+			}
 		, whereisKey = Nothing
 		, remoteFsck = Nothing
 		, repairRepo = Nothing
@@ -103,3 +119,51 @@ borgSetup _ mu _ c _gc = do
 
 borgLocal :: BorgRepo -> Bool
 borgLocal = notElem ':'
+
+listImportableContentsM :: BorgRepo -> Annex (Maybe (ImportableContents (ContentIdentifier, ByteSize)))
+listImportableContentsM borgrepo = error "TODO"
+
+-- Since this remote is thirdPartyPopulated, this needs to
+-- find only those ImportLocations that are annex object files. All other
+-- files in the borg backup are ignored.
+importKeyM :: ImportLocation -> ContentIdentifier -> ByteSize -> MeterUpdate -> Annex (Maybe Key)
+importKeyM loc cid sz _ = return $ case deserializeKey' f of
+	Just k
+		-- Annex objects always are in a subdirectory with the same
+		-- name as the filename. If this is not the case for the file
+		-- that was backed up, it is probably not a valid annex object.
+		-- Eg, it could be something in annex/bad/, or annex/tmp/.
+		-- Or it could be a file that only happens to have a name
+		-- like an annex object.
+		-- (This does unfortunately prevent recognizing files that are
+		-- part of special remotes that don't use that layout. The most
+		-- likely special remote to be in a backup, the directory
+		-- special remote, does use that layout at least.)
+		| lastMaybe (P.splitDirectories (P.dropFileName p)) /= Just f -> Nothing
+		-- Chunked or encrypted keys used in special remotes are not
+		-- supported.
+		| isChunkKey k || isEncKey k -> Nothing
+		-- Check that the size of the key is the same as the size of the
+		-- file stored in borg. This is a cheap way to make sure it's
+		-- probabably the actual content of the file. We don't fully
+		-- verify the content here because that could be a very 
+		-- expensive operation for a large repository; if the user
+		-- wants to detect every possible data corruption problem
+		-- (eg, wrong data read off disk during backup, or the object
+		-- was corrupt in the git-annex repo and that bad object got
+		-- backed up), they can fsck the remote.
+		| otherwise -> case fromKey keySize k of
+			Just sz'
+				| sz' == sz -> Just k
+				| otherwise -> Nothing
+			Nothing -> Just k
+	Nothing -> Nothing
+  where
+	p = fromImportLocation loc
+	f = P.takeFileName p
+
+retrieveExportWithContentIdentifierM :: BorgRepo -> ImportLocation -> ContentIdentifier -> FilePath -> Annex Key -> MeterUpdate -> Annex Key
+retrieveExportWithContentIdentifierM borgrepo loc cid dest k p = error "TODO"
+
+checkPresentExportWithContentIdentifierM :: BorgRepo -> Key -> ImportLocation -> [ContentIdentifier] -> Annex Bool
+checkPresentExportWithContentIdentifierM borgrepo k loc cids = error "TODO"

Remote/Directory.hs

@@ -370,8 +370,8 @@ guardSameContentIdentifiers cont old new
 	| new == Just old = cont
 	| otherwise = giveup "file content has changed"
 
-importKeyM :: RawFilePath -> ExportLocation -> ContentIdentifier -> MeterUpdate -> Annex (Maybe Key)
-importKeyM dir loc cid p = do
+importKeyM :: RawFilePath -> ExportLocation -> ContentIdentifier -> ByteSize -> MeterUpdate -> Annex (Maybe Key)
+importKeyM dir loc cid _sz p = do
 	backend <- chooseBackend f
 	k <- fst <$> genKey ks p backend
 	currcid <- liftIO $ mkContentIdentifier absf

Types/Remote.hs

@@ -299,7 +299,7 @@ data ImportActions a = ImportActions
 	-- otherwise return Nothing.
 	--
 	-- Throws exception on failure to access the remote.
-	, importKey :: Maybe (ImportLocation -> ContentIdentifier -> MeterUpdate -> a (Maybe Key))
+	, importKey :: Maybe (ImportLocation -> ContentIdentifier -> ByteSize -> MeterUpdate -> a (Maybe Key))
 	-- Retrieves a file from the remote. Ensures that the file
 	-- it retrieves has the requested ContentIdentifier.
 	--