improve display when lockcontent fails

/dev/null stderr; ssh is still able to display a password prompt
despite this

Show some messages so the user knows it's locking a remote, and
knows if that locking failed.

Remote/Git.hs

@@ -364,7 +364,7 @@ dropKey r key
 lockKey :: Remote -> Key -> (VerifiedCopy -> Annex r) -> Annex r
 lockKey r key callback
 	| not $ Git.repoIsUrl (repo r) =
-		guardUsable (repo r) cantlock $ do
+		guardUsable (repo r) failedlock $ do
 			inorigrepo <- Annex.makeRunner
 			-- Lock content from perspective of remote,
 			-- and then run the callback in the original
@@ -372,13 +372,17 @@ lockKey r key callback
 			onLocal r $ Annex.Content.lockContentShared key $ 
 				liftIO . inorigrepo . callback
 	| Git.repoIsSsh (repo r) = do
+		showLocking r
 		Just (cmd, params) <- Ssh.git_annex_shell (repo r) "lockcontent"
 			[Param $ key2file key] []
-		(Just hin, Just hout, Nothing, p) <- liftIO $ createProcess $
-			 (proc cmd (toCommand params))
-				{ std_in = CreatePipe
-				, std_out = CreatePipe
-				}
+		(Just hin, Just hout, Nothing, p) <- liftIO $ 
+			withFile devNull WriteMode $ \nullh ->
+				createProcess $
+					 (proc cmd (toCommand params))
+						{ std_in = CreatePipe
+						, std_out = CreatePipe
+						, std_err = UseHandle nullh
+						}
 		-- Wait for either the process to exit, or for it to
 		-- indicate the content is locked.
 		v <- liftIO $ race 
@@ -393,21 +397,23 @@ lockKey r key callback
 		let checkexited = not . isJust <$> getProcessExitCode p
 		case v of
 			Left _exited -> do
+				showNote "lockcontent failed"
 				liftIO $ do
 					hClose hin
 					hClose hout
-				cantlock
+				failedlock
 			Right l 
 				| l == Ssh.contentLockedMarker -> bracket_
 					noop
 					signaldone 
 					(withVerifiedCopy LockedCopy r checkexited callback)
 				| otherwise -> do
+					showNote "lockcontent failed"
 					signaldone
-					cantlock
-	| otherwise = cantlock
+					failedlock
+	| otherwise = failedlock
   where
-	cantlock = error "can't lock content"
+	failedlock = error "can't lock content"
 
 {- Tries to copy a key's content from a remote's annex to a file. -}
 copyFromRemote :: Remote -> Key -> AssociatedFile -> FilePath -> MeterUpdate -> Annex (Bool, Verification)

Remote/Helper/Messages.hs

@@ -13,20 +13,23 @@ import Common.Annex
 import qualified Git
 import qualified Types.Remote as Remote
 
-class Checkable a where
-	descCheckable :: a -> String
+class Describable a where
+	describe :: a -> String
 
-instance Checkable Git.Repo where
-	descCheckable = Git.repoDescribe
+instance Describable Git.Repo where
+	describe = Git.repoDescribe
 
-instance Checkable (Remote.RemoteA a) where
-	descCheckable = Remote.name
+instance Describable (Remote.RemoteA a) where
+	describe = Remote.name
 
-instance Checkable String where
-	descCheckable = id
+instance Describable String where
+	describe = id
 
-showChecking :: Checkable a => a -> Annex ()
-showChecking v = showAction $ "checking " ++ descCheckable v
+showChecking :: Describable a => a -> Annex ()
+showChecking v = showAction $ "checking " ++ describe v
 
-cantCheck :: Checkable a => a -> e
-cantCheck v = error $ "unable to check " ++ descCheckable v
+cantCheck :: Describable a => a -> e
+cantCheck v = error $ "unable to check " ++ describe v
+
+showLocking :: Describable a => a -> Annex ()
+showLocking v = showAction $ "locking " ++ describe v

debian/changelog

@@ -5,6 +5,15 @@ git-annex (5.20150931) UNRELEASED; urgency=medium
     all copies of its content being lost.
   * git-annex-shell: Added lockcontent command, to prevent dropping of
     a key's content. This is necessary due to the above bugfix.
+  * In some cases, the above bugfix changes what git-annex allows to be dropped:
+    - When a file is present in several special remotes,
+      but not in any accessible git repositories, dropping it from one of
+      the special remotes will now fail. Instead, the file has to be
+      moved from one of the special remotes to the git repository, and can
+      then safely be dropped from the git repository.
+    - If a git remote has too old a version of git-annex-shell installed,
+      git-annex won't trust it to hold onto a copy of a file when dropping
+      that file from some other remote.
   * Do verification of checksums of annex objects downloaded from remotes.
   * When annex objects are received into git repositories from other git
     repos, their checksums are verified then too.