gcrypt: now supports rsync

Use rsync for gcrypt remotes that are not local to the disk.
(Note that I have punted on supporting http transport for now, it doesn't
seem likely to be very useful.)

This was mostly quite easy, it just uses the rsync special remote to handle
the transfers. The git repository url is converted to a RsyncOptions
structure, which required parsing it separately, since the rsync special
remote only supports rsync urls, which use a different format.

Note that annexed objects are now stored at the top of the gcrypt repo,
rather than inside annex/objects. This simplified the rsync suport,
since it doesn't have to arrange to create that directory. And git-annex
is not going to be run directly within gcrypt repos -- or if in some
strance scenario it was, it would make sense for it to not see the
encrypted objects.

This commit was sponsored by Sheila Miguez

Remote/Rsync.hs

@@ -7,7 +7,16 @@
 
 {-# LANGUAGE CPP #-}
 
-module Remote.Rsync (remote) where
+module Remote.Rsync (
+	remote,
+	storeEncrypted,
+	retrieveEncrypted,
+	remove,
+	checkPresent,
+	withRsyncScratchDir,
+	genRsyncOpts,
+	RsyncOpts
+) where
 
 import qualified Data.ByteString.Lazy as L
 import qualified Data.Map as M
@@ -52,9 +61,10 @@ remote = RemoteType {
 gen :: Git.Repo -> UUID -> RemoteConfig -> RemoteGitConfig -> Annex Remote
 gen r u c gc = do
 	cst <- remoteCost gc expensiveRemoteCost
-	(transport, url) <- rsyncTransport
-	let o = RsyncOpts url (transport ++ opts) escape
-	    islocal = rsyncUrlIsPath $ rsyncUrl o
+	(transport, url) <- rsyncTransport gc $
+		fromMaybe (error "missing rsyncurl") $ remoteAnnexRsyncUrl gc
+	let o = genRsyncOpts c gc transport url
+	let islocal = rsyncUrlIsPath $ rsyncUrl o
 	return $ encryptableRemote c
 		(storeEncrypted o $ getGpgEncParams (c,gc))
 		(retrieveEncrypted o)
@@ -79,6 +89,9 @@ gen r u c gc = do
 			, globallyAvailable = not $ islocal
 			, remotetype = remote
 			}
+
+genRsyncOpts :: RemoteConfig -> RemoteGitConfig -> [CommandParam] -> RsyncUrl -> RsyncOpts
+genRsyncOpts c gc transport url = RsyncOpts url (transport ++ opts) escape
   where
 	opts = map Param $ filter safe $ remoteAnnexRsyncOptions gc
 	escape = M.lookup "shellescape" c /= Just "no"
@@ -89,28 +102,30 @@ gen r u c gc = do
 		| opt == "--delete" = False
 		| opt == "--delete-excluded" = False
 		| otherwise = True
-	rawurl = fromMaybe (error "missing rsyncurl") $ remoteAnnexRsyncUrl gc
+
+rsyncTransport :: RemoteGitConfig -> RsyncUrl -> Annex ([CommandParam], RsyncUrl)
+rsyncTransport gc rawurl
+	| rsyncUrlIsShell rawurl =
+		(\rsh -> return (rsyncShell rsh, resturl)) =<<
+		case fromNull ["ssh"] (remoteAnnexRsyncTransport gc) of
+			"ssh":sshopts -> do
+				let (port, sshopts') = sshReadPort sshopts
+				    host = takeWhile (/=':') resturl
+				-- Connection caching
+				(Param "ssh":) <$> sshCachingOptions
+					(host, port)
+					(map Param $ loginopt ++ sshopts')
+			"rsh":rshopts -> return $ map Param $ "rsh" :
+				loginopt ++ rshopts
+			rsh -> error $ "Unknown Rsync transport: "
+				++ unwords rsh
+	| otherwise = return ([], rawurl)
+  where
 	(login,resturl) = case separate (=='@') rawurl of
-			(h, "") -> (Nothing, h)
-			(l, h)  -> (Just l, h)
+		(h, "") -> (Nothing, h)
+		(l, h)  -> (Just l, h)
 	loginopt = maybe [] (\l -> ["-l",l]) login
-	fromNull as xs | null xs = as
-		       | otherwise = xs
-	rsyncTransport = if rsyncUrlIsShell rawurl
-		then (\rsh -> return (rsyncShell rsh, resturl)) =<<
-			case fromNull ["ssh"] (remoteAnnexRsyncTransport gc) of
-				"ssh":sshopts -> do
-					let (port, sshopts') = sshReadPort sshopts
-					    host = takeWhile (/=':') resturl
-					-- Connection caching
-					(Param "ssh":) <$> sshCachingOptions
-						(host, port)
-						(map Param $ loginopt ++ sshopts')
-				"rsh":rshopts -> return $ map Param $ "rsh" :
-					loginopt ++ rshopts
-				rsh -> error $ "Unknown Rsync transport: "
-					++ unwords rsh
-		else return ([], rawurl)
+	fromNull as xs = if null xs then as else xs
 
 rsyncSetup :: Maybe UUID -> RemoteConfig -> Annex (RemoteConfig, UUID)
 rsyncSetup mu c = do