working toward git-remote-annex using a special remote

Not quite there yet.

Also, changed the format of GITBUNDLE keys to use only one '-'
after the UUID. A sha256 does not contain that character, so can just
split at the last one.

Amusingly, the sha256 will probably not actually be verified. A git
bundle contains its own checksums that git uses to verify it. And if
someone wanted to replace the content of a GITBUNDLE object, they
could just edit the manifest to use a new one whose sha256 does verify.

Sponsored-by: Nicholas Golder-Manning

CmdLine/GitRemoteAnnex.hs

@@ -5,38 +5,53 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module CmdLine.GitRemoteAnnex where
 
 import Annex.Common
 import qualified Annex
 import qualified Git.CurrentRepo
+import qualified Remote
 import Annex.UUID
+import Types.Remote
+import Types.Key
 import Network.URI
+import Utility.Tmp
+import Utility.Metered
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Char8 as B8
+import qualified Data.ByteString.Short as S
 
 run :: [String] -> IO ()
 run (_remotename:url:[]) = case parseSpecialRemoteUrl url of
 	Left e -> giveup e
 	Right src -> do
 		state <- Annex.new =<< Git.CurrentRepo.get
-		Annex.eval state (run' url)
+		Annex.eval state (run' src)
 run (_remotename:[]) = giveup "remote url not configured"
 run _ = giveup "expected remote name and url parameters"
 
-run' :: String -> Annex ()
-run' url = go =<< lines <$> liftIO getContents
+run' :: SpecialRemoteConfig -> Annex ()
+run' src =
+	-- Prevent any usual git-annex output to stdout, because
+	-- the output of this command is being parsed by git.
+	doQuietAction $ do
+		rmt <- getSpecialRemote src
+		go rmt =<< lines <$> liftIO getContents
   where
-	go (l:ls) =
+	go rmt (l:ls) =
 		let (c, v) = splitLine l
 		in case c of
-			"capabilities" -> capabilities >> go ls	
+			"capabilities" -> capabilities >> go rmt ls	
 			"list" -> case v of
-				"" -> list False >> go ls
-				"for-push" -> list True >> go ls
+				"" -> list rmt False >> go rmt ls
+				"for-push" -> list rmt True >> go rmt ls
 				_ -> protocolError l
-			"fetch" -> fetch (l:ls) >>= go
-			"push" -> push (l:ls) >>= go
+			"fetch" -> fetch rmt (l:ls) >>= go rmt
+			"push" -> push rmt (l:ls) >>= go rmt
 			_ -> protocolError l
-	go [] = return ()
+	go _ [] = return ()
 
 protocolError :: String -> a
 protocolError l = giveup $ "gitremote-helpers protocol error at " ++ show l
@@ -48,30 +63,30 @@ capabilities = do
 	liftIO $ putStrLn ""
 	liftIO $ hFlush stdout
 
-list :: Bool -> Annex ()
-list forpush = error "TODO list" 
+list :: Remote -> Bool -> Annex ()
+list rmt forpush = error "TODO list" 
 
 -- Any number of fetch commands can be sent by git, asking for specific
 -- things. We fetch everything new at once, so find the end of the fetch
 -- commands (which is supposed to be a blank line) before fetching. 
-fetch :: [String] -> Annex [String]
-fetch (l:ls) = case splitLine l of
-	("fetch", _) -> fetch ls
+fetch :: Remote -> [String] -> Annex [String]
+fetch rmt (l:ls) = case splitLine l of
+	("fetch", _) -> fetch rmt ls
 	("", _) -> do
-		fetch'
+		fetch' rmt
 		return ls
 	_ -> do
-		fetch'
+		fetch' rmt
 		return (l:ls)
-fetch [] = do
-	fetch'
+fetch rmt [] = do
+	fetch' rmt
 	return []
 
-fetch' :: Annex ()
-fetch' = error "TODO fetch"
+fetch' :: Remote -> Annex ()
+fetch' rmt = error "TODO fetch"
 
-push :: [String] -> Annex [String]
-push ls = do
+push :: Remote -> [String] -> Annex [String]
+push rmt ls = do
 	let (refspecs, ls') = collectRefSpecs ls
 	error "TODO push refspecs"
 	return ls'
@@ -135,7 +150,76 @@ parseSpecialRemoteUrl s = case parseURI s of
 		_ -> Left "Not an annex: URL"
   where
 	parsequery u = map parsekv $ splitc '&' (drop 1 (uriQuery u))
-	parsekv s =
-		let (k, sv) = break (== '=') s
+	parsekv kv =
+		let (k, sv) = break (== '=') kv
 		    v = if null sv then sv else drop 1 sv
 		in (unEscapeString k, unEscapeString v)
+
+getSpecialRemote :: SpecialRemoteConfig -> Annex Remote
+getSpecialRemote src
+	-- annex:uuid with no query string uses an existing remote
+	| null (specialRemoteParams src) = 
+		Remote.byUUID (specialRemoteUUID src) >>= \case
+			Just rmt -> if thirdPartyPopulated (remotetype rmt) 
+				then giveup "Cannot use this thirdparty-populated special remote as a git remote"
+				else return rmt
+			Nothing -> giveup $ "Cannot find an existing special remote with UUID " 
+				++ fromUUID (specialRemoteUUID src)
+	-- Given the configuration of a special remote, create a
+	-- Remote object to access the special remote.
+	-- This needs to avoid storing the configuration in the git-annex
+	-- branch (which would be redundant and also the configuration
+	-- provided may differ in some small way from the configuration
+	-- that is stored in the git repository inside the remote, which
+	-- should not be changed). It also needs to avoid creating a git
+	-- remote in .git/config.
+	| otherwise = error "TODO conjure up a new special remote out of thin air"
+	-- XXX one way to do it would be to make a temporary git repo,
+	-- initremote in there, and use that for accessing the special
+	-- remote, rather than the current git repo. But can this be
+	-- avoided?
+
+-- A key that is used for the manifest of the git repository stored in a
+-- special remote with the specified uuid.
+manifestKey :: UUID -> Key
+manifestKey u = mkKey $ \kd -> kd
+	{ keyName = S.toShort (fromUUID u)
+	, keyVariety = OtherKey "GITMANIFEST"
+	}
+
+-- A key that is used for the git bundle with the specified sha256
+-- that is stored in a special remote with the specified uuid.
+gitbundleKey :: UUID -> B.ByteString -> Key
+gitbundleKey u sha256 = mkKey $ \kd -> kd
+	{ keyName = S.toShort (fromUUID u <> "-" <> sha256)
+	, keyVariety = OtherKey "GITBUNDLE"
+	}
+
+-- The manifest contains an ordered list of git bundle keys.
+newtype Manifest = Manifest [Key]
+
+-- Downloads the Manifest, or if it does not exist, returns an empty
+-- Manifest.
+--
+-- Throws errors if the remote cannot be accessed or the download fails,
+-- or if the manifest file cannot be parsed.
+downloadManifest :: Remote -> Annex Manifest
+downloadManifest rmt = ifM (checkPresent rmt mk)
+	( withTmpFile "GITMANIFEST" $ \tmp tmph -> do
+		liftIO $ hClose tmph
+		_ <- retrieveKeyFile rmt mk
+			(AssociatedFile Nothing) tmp
+			nullMeterUpdate NoVerify
+		ks <- map deserializeKey' . B8.lines <$> liftIO (B.readFile tmp)
+		Manifest <$> checkvalid [] ks
+	, return (Manifest [])
+	)
+  where
+	mk = manifestKey (Remote.uuid rmt)
+
+	checkvalid c [] = return (reverse c)
+	checkvalid c (Just k:ks) = case fromKey keyVariety k of
+		OtherKey "GITBUNDLE" -> checkvalid (k:c) ks
+		_ -> giveup $ "Wrong type of key in manifest " ++ serializeKey k
+	checkvalid _ (Nothing:_) =
+		giveup $ "Error parsing manifest " ++ serializeKey mk

Command/Fsck.hs

@@ -38,6 +38,7 @@ import Utility.CopyFile
 import Git.FilePath
 import Utility.PID
 import Utility.InodeCache
+import Utility.Metered
 import Annex.InodeSentinal
 import qualified Database.Keys
 import qualified Database.Fsck as FsckDb
@@ -206,8 +207,7 @@ performRemote key afile numcopies remote =
 			)
 		, return Nothing
 		)
-	getfile' tmp = Remote.retrieveKeyFile remote key (AssociatedFile Nothing) (fromRawFilePath tmp) dummymeter (RemoteVerify remote)
-	dummymeter _ = noop
+	getfile' tmp = Remote.retrieveKeyFile remote key (AssociatedFile Nothing) (fromRawFilePath tmp) nullMeterUpdate (RemoteVerify remote)
 	getcheap tmp = case Remote.retrieveKeyFileCheap remote of
 		Just a -> isRight <$> tryNonAsync (a key afile (fromRawFilePath tmp))
 		Nothing -> return False

doc/internals/git-remote-annex.mdwn

@@ -3,11 +3,13 @@ This adds two new object types to git-annex, GITMANIFEST and a GITBUNDLE.
 GITMANIFEST--$UUID is the manifest for a git repository stored in the
 git-annex repository with that UUID.
 
-GITBUNDLE--$UUID--sha256 is a git bundle.
+GITBUNDLE--$UUID-sha256 is a git bundle.
 
 # format of the manifest file
 
-An ordered list of bundle keys, one per line.
+An ordered list of bundle keys, one per line. 
+
+(Lines end with unix `"\n"`, not `"\r\n"`.)
 
 # fetching