implement exporttree=yes configuration

* Only export to remotes that were initialized to support it.
* Prevent storing key/value on export remotes.
* Prevent enabling exporttree=yes and encryption in the same remote.

SetupStage Enable was changed to take the old RemoteConfig.
This allowed only setting exporttree when initially setting up a
remote, and not configuring it later after stuff might already be stored
in the remote.

Went with =yes rather than =true for consistency with other parts of
git-annex. Changed docs accordingly.

This commit was supported by the NSF-funded DataLad project.

Annex/SpecialRemote.hs

@@ -81,7 +81,7 @@ autoEnable = do
 			(Just name, Right t) -> whenM (canenable u) $ do
 				showSideAction $ "Auto enabling special remote " ++ name
 				dummycfg <- liftIO dummyRemoteGitConfig
-				res <- tryNonAsync $ setup t Enable (Just u) Nothing c dummycfg
+				res <- tryNonAsync $ setup t (Enable c) (Just u) Nothing c dummycfg
 				case res of
 					Left e -> warning (show e)
 					Right _ -> return ()

Assistant/MakeRemote.hs

@@ -52,7 +52,7 @@ makeRsyncRemote name location = makeRemote name location $ const $ void $
 	go Nothing = setupSpecialRemote name Rsync.remote config Nothing
 		(Nothing, R.Init, Annex.SpecialRemote.newConfig name)
 	go (Just (u, c)) = setupSpecialRemote name Rsync.remote config Nothing
-		(Just u, R.Enable, c)
+		(Just u, R.Enable c, c)
 	config = M.fromList
 		[ ("encryption", "shared")
 		, ("rsyncurl", location)
@@ -91,7 +91,7 @@ enableSpecialRemote name remotetype mcreds config = do
 	r <- Annex.SpecialRemote.findExisting name
 	case r of
 		Nothing -> error $ "Cannot find a special remote named " ++ name
-		Just (u, c) -> setupSpecialRemote' False name remotetype config mcreds (Just u, R.Enable, c)
+		Just (u, c) -> setupSpecialRemote' False name remotetype config mcreds (Just u, R.Enable c, c)
 
 setupSpecialRemote :: RemoteName -> RemoteType -> R.RemoteConfig -> Maybe CredPair -> (Maybe UUID, R.SetupStage, R.RemoteConfig) -> Annex RemoteName
 setupSpecialRemote = setupSpecialRemote' True

Command/EnableRemote.hs

@@ -81,11 +81,11 @@ startSpecialRemote name config (Just (u, c)) = do
 	gc <- maybe (liftIO dummyRemoteGitConfig) 
 		(return . Remote.gitconfig)
 		=<< Remote.byUUID u
-	next $ performSpecialRemote t u fullconfig gc
+	next $ performSpecialRemote t u c fullconfig gc
 
-performSpecialRemote :: RemoteType -> UUID -> R.RemoteConfig -> RemoteGitConfig -> CommandPerform
-performSpecialRemote t u c gc = do
-	(c', u') <- R.setup t R.Enable (Just u) Nothing c gc
+performSpecialRemote :: RemoteType -> UUID -> R.RemoteConfig -> R.RemoteConfig -> RemoteGitConfig -> CommandPerform
+performSpecialRemote t u oldc c gc = do
+	(c', u') <- R.setup t (R.Enable oldc) (Just u) Nothing c gc
 	next $ cleanupSpecialRemote u' c'
 
 cleanupSpecialRemote :: UUID -> R.RemoteConfig -> CommandCleanup

Remote/Directory.hs

@@ -37,14 +37,14 @@ remote = RemoteType {
 	typename = "directory",
 	enumerate = const (findSpecialRemotes "directory"),
 	generate = gen,
-	setup = directorySetup
+	setup = exportableRemoteSetup directorySetup
 }
 
 gen :: Git.Repo -> UUID -> RemoteConfig -> RemoteGitConfig -> Annex (Maybe Remote)
 gen r u c gc = do
 	cst <- remoteCost gc cheapRemoteCost
 	let chunkconfig = getChunkConfig c
-	return $ Just $ specialRemote c
+	return $ Just $ exportableRemote $ specialRemote c
 		(prepareStore dir chunkconfig)
 		(retrieve dir chunkconfig)
 		(simplyPrepare $ remove dir)

Remote/Git.hs

@@ -111,7 +111,7 @@ gitSetup Init mu _ c _ = do
 	if isNothing mu || mu == Just u
 		then return (c, u)
 		else error "git remote did not have specified uuid"
-gitSetup Enable (Just u) _ c _ = do
+gitSetup (Enable _) (Just u) _ c _ = do
 	inRepo $ Git.Command.run
 		[ Param "remote"
 		, Param "add"
@@ -119,7 +119,7 @@ gitSetup Enable (Just u) _ c _ = do
 		, Param $ fromMaybe (giveup "no location") (M.lookup "location" c)
 		]
 	return (c, u)
-gitSetup Enable Nothing _ _ _ = error "unable to enable git remote with no specified uuid"
+gitSetup (Enable _) Nothing _ _ _ = error "unable to enable git remote with no specified uuid"
 
 {- It's assumed to be cheap to read the config of non-URL remotes, so this is
  - done each time git-annex is run in a way that uses remotes.

Remote/Glacier.hs

@@ -89,8 +89,9 @@ glacierSetup' ss u mcreds c gc = do
 	(c', encsetup) <- encryptionSetup c gc
 	c'' <- setRemoteCredPair encsetup c' gc (AWS.creds u) mcreds
 	let fullconfig = c'' `M.union` defaults
-	when (ss == Init) $
-		genVault fullconfig gc u
+	case ss of
+		Init -> genVault fullconfig gc u
+		_ -> return ()
 	gitConfigSpecialRemote u fullconfig "glacier" "true"
 	return (fullconfig, u)
   where

Remote/Helper/Encryptable.hs

@@ -15,6 +15,7 @@ module Remote.Helper.Encryptable (
 	embedCreds,
 	cipherKey,
 	extractCipher,
+	isEncrypted,
 	describeEncryption,
 ) where
 
@@ -57,7 +58,7 @@ encryptionSetup c gc = do
 	encryption = M.lookup "encryption" c
 	-- Generate a new cipher, depending on the chosen encryption scheme
 	genCipher cmd = case encryption of
-		_ | M.member "cipher" c || M.member "cipherkeys" c || M.member "pubkeys" c -> cannotchange
+		_ | hasEncryptionConfig c -> cannotchange
 		Just "none" -> return (c, NoEncryption)
 		Just "shared" -> encsetup $ genSharedCipher cmd
 		-- hybrid encryption is the default when a keyid is
@@ -167,6 +168,15 @@ extractCipher c = case (M.lookup "cipher" c,
   where
 	readkeys = KeyIds . splitc ','
 
+isEncrypted :: RemoteConfig -> Bool
+isEncrypted c = case M.lookup "encryption" c of
+	Just "none" -> False
+	Just _ -> True
+	Nothing -> hasEncryptionConfig c
+
+hasEncryptionConfig :: RemoteConfig -> Bool
+hasEncryptionConfig c = M.member "cipher" c || M.member "cipherkeys" c || M.member "pubkeys" c
+
 describeEncryption :: RemoteConfig -> String
 describeEncryption c = case extractCipher c of
 	Nothing -> "none"

Remote/Helper/Export.hs

@@ -9,7 +9,12 @@ module Remote.Helper.Export where
 
 import Annex.Common
 import Types.Remote
+import Types.Creds
+import Remote.Helper.Encryptable (isEncrypted)
 
+import qualified Data.Map as M
+
+-- | Use for remotes that do not support exports.
 exportUnsupported :: ExportActions Annex
 exportUnsupported = ExportActions
 	{ exportSupported = return False
@@ -19,3 +24,28 @@ exportUnsupported = ExportActions
 	, checkPresentExport = \_ _ -> return False
 	, renameExport = \_ _ _ -> return False
 	}
+
+-- | A remote that supports exports when configured with exporttree=yes,
+-- and otherwise does not.
+exportableRemote :: Remote -> Remote
+exportableRemote r = case M.lookup "exporttree" (config r) of
+	Just "yes" -> r
+		{ storeKey = \_ _ _ -> do
+			warning "remote is configured with exporttree=yes; use `git-annex export` to store content on it"
+			return False
+		}
+	_ -> r
+		{ exportActions = exportUnsupported }
+
+exportableRemoteSetup :: (SetupStage -> Maybe UUID -> Maybe CredPair -> RemoteConfig -> RemoteGitConfig -> Annex (RemoteConfig, UUID)) -> SetupStage -> Maybe UUID -> Maybe CredPair -> RemoteConfig -> RemoteGitConfig -> Annex (RemoteConfig, UUID)
+exportableRemoteSetup setupaction st mu cp c gc = case st of
+	Init -> case M.lookup "exporttree" c of
+		Just "yes" | isEncrypted c ->
+			giveup "cannot enable both encryption and exporttree"
+		_ -> cont
+	Enable oldc
+		| M.lookup "exporttree" c /= M.lookup "exporttree" oldc ->
+			giveup "cannot change exporttree of existing special remote"
+		| otherwise -> cont
+  where
+	cont = setupaction st mu cp c gc

Remote/S3.hs

@@ -129,8 +129,9 @@ s3Setup' ss u mcreds c gc
 		(c', encsetup) <- encryptionSetup c gc
 		c'' <- setRemoteCredPair encsetup c' gc (AWS.creds u) mcreds
 		let fullconfig = c'' `M.union` defaults
-		when (ss == Init) $
-			genBucket fullconfig gc u
+		case ss of
+			Init -> genBucket fullconfig gc u
+			_ -> return ()
 		use fullconfig
 
 	archiveorg = do

Types/Remote.hs

@@ -44,8 +44,7 @@ type RemoteConfigKey = String
 
 type RemoteConfig = M.Map RemoteConfigKey String
 
-data SetupStage = Init | Enable
-	deriving (Eq)
+data SetupStage = Init | Enable RemoteConfig
 
 {- There are different types of remotes. -}
 data RemoteTypeA a = RemoteType {

doc/design/exporting_trees_to_special_remotes.mdwn

@@ -15,13 +15,13 @@ when they want to export a tree. (It would also be possible to drop all content
 from an existing special remote and reuse it, but there does not seem much
 benefit in doing so.)
 
-Add a new `initremote` configuration `exporttree=true`, that cannot be
+Add a new `initremote` configuration `exporttree=yes`, that cannot be
 changed by `enableremote`:
 
-	git annex initremote myexport type=... exporttree=true
+	git annex initremote myexport type=... exporttree=yes
 
-It does not make sense to encrypt an export, so exporttree=true requires
-(and can even imply) encryption=false.
+It does not make sense to encrypt an export, so exporttree=yes requires
+encryption=none.
 
 Note that the particular tree to export is not specified yet. This is
 because the tree that is exported to a special remote may change.
@@ -137,7 +137,7 @@ key/value stores. The content of a file can change, and if multiple
 repositories can export a special remote, they can be out of sync about
 what files are exported to it. 
 
-Possible solution: Make exporttree=true cause the special remote to
+Possible solution: Make exporttree=yes cause the special remote to
 be untrusted, and rely on annex.verify to catch cases where the content
 of a file on a special remote has changed. This would work well enough
 except for when the WORM or URL backend is used. So, prevent the user

doc/git-annex-export.mdwn

@@ -15,7 +15,7 @@ keys. That is great for data storage, but your filenames are obscured.
 Exporting replicates the tree to the special remote as-is.
 
 Mixing key/value and exports in the same remote would be a mess and so is
-not allowed. So, you have to configure a remote with `exporttree=true`
+not allowed. So, you have to configure a remote with `exporttree=yes`
 when initially setting it up with [[git-annex-initremote]](1).
 
 Repeated exports are done efficiently, by diffing the old and new tree,

doc/special_remotes/directory.mdwn

@@ -31,7 +31,7 @@ remote:
   Do not use for new remotes. It is not safe to change the chunksize
   setting of an existing remote.
 
-* `exporttree` - Set to "true" to make this special remote usable
+* `exporttree` - Set to "yes" to make this special remote usable
   by [[git-annex-export]]. It will not be usable as a general-purpose
   special remote.
 

doc/todo/export.mdwn

@@ -17,12 +17,9 @@ there need to be a new interface in supported remotes?
 
 Work is in progress. Todo list:
 
-* Only export to remotes that were initialized to support it.
-* Prevent using export remotes for key/value storage.
 * Use retrieveExport when getting from export remotes.
+  (Needs a map from key to ExportLocation)
 * Efficient handling of renames.
-* Support export to aditional special remotes (S3 etc)
-* Support export to external special remotes.
 * If the same content is present in two different files, export
   location tracking can be messed up. 
   
@@ -33,3 +30,5 @@ Work is in progress. Todo list:
   And, once one of the files is uploaded, the location log will
   say the content is present, so the pass over the tree won't try to
   upload the other file. (See design for a fix for this.)
+* Support export to aditional special remotes (S3 etc)
+* Support export to external special remotes.