Run ssh with -n whenever input is not being piped into it

... to avoid it consuming stdin that it shouldn't.

This fixes git-annex-checkpresentkey --batch remote, which didn't output
results for all keys passed into it.

Other git-annex commands that communicate with a remote over ssh may also
have been consuming stdin that they shouldn't have, which could have
impacted using them in eg, shell scripts. For example, a shell script
reading files from stdin and passing them to git annex drop would be
impacted by this bug, whenever git annex drop ran git-annex-shell
checkpresent, it would consume part/all of the stdin that the shell script
was supposed to consume.

Fixed by adding a ConsumeStdin parameter to Annex.Ssh.sshOptions, which
is used throughout git-annex to run ssh (in order for ssh connection
caching to work). Every call site was checked to see if it used
CreatePipe for stdin, and if not was marked NoConsumeStdin.

Remote/Ddar.hs

@@ -118,11 +118,11 @@ splitRemoteDdarRepo ddarrepo =
 
 {- Return the command and parameters to use for a ddar call that may need to be
  - made on a remote repository. This will call ssh if needed. -}
-ddarRemoteCall :: DdarRepo -> Char -> [CommandParam] -> Annex (String, [CommandParam])
-ddarRemoteCall ddarrepo cmd params
+ddarRemoteCall :: ConsumeStdin -> DdarRepo -> Char -> [CommandParam] -> Annex (String, [CommandParam])
+ddarRemoteCall cs ddarrepo cmd params
 	| ddarLocal ddarrepo = return ("ddar", localParams)
 	| otherwise = do
-		os <- sshOptions (host, Nothing) (ddarRepoConfig ddarrepo) []
+		os <- sshOptions cs (host, Nothing) (ddarRepoConfig ddarrepo) []
 		return ("ssh", os ++ remoteParams)
   where
 	(host, ddarrepo') = splitRemoteDdarRepo ddarrepo
@@ -130,13 +130,13 @@ ddarRemoteCall ddarrepo cmd params
 	remoteParams = Param host : Param "ddar" : Param [cmd] : Param ddarrepo' : params
 
 {- Specialized ddarRemoteCall that includes extraction command and flags -}
-ddarExtractRemoteCall :: DdarRepo -> Key -> Annex (String, [CommandParam])
-ddarExtractRemoteCall ddarrepo k =
-	ddarRemoteCall ddarrepo 'x' [Param "--force-stdout", Param $ key2file k]
+ddarExtractRemoteCall :: ConsumeStdin -> DdarRepo -> Key -> Annex (String, [CommandParam])
+ddarExtractRemoteCall cs ddarrepo k =
+	ddarRemoteCall cs ddarrepo 'x' [Param "--force-stdout", Param $ key2file k]
 
 retrieve :: DdarRepo -> Retriever
 retrieve ddarrepo = byteRetriever $ \k sink -> do
-	(cmd, params) <- ddarExtractRemoteCall ddarrepo k
+	(cmd, params) <- ddarExtractRemoteCall NoConsumeStdin ddarrepo k
 	let p = (proc cmd $ toCommand params) { std_out = CreatePipe }
 	(_, Just h, _, pid) <- liftIO $ createProcess p
 	liftIO (hClose h >> forceSuccessProcess p pid)
@@ -147,7 +147,8 @@ retrieveCheap _ _ _ = return False
 
 remove :: DdarRepo -> Remover
 remove ddarrepo key = do
-	(cmd, params) <- ddarRemoteCall ddarrepo 'd' [Param $ key2file key]
+	(cmd, params) <- ddarRemoteCall NoConsumeStdin ddarrepo 'd'
+		[Param $ key2file key]
 	liftIO $ boolSystem cmd params
 
 ddarDirectoryExists :: DdarRepo -> Annex (Either String Bool)
@@ -158,7 +159,8 @@ ddarDirectoryExists ddarrepo
 			Left _ -> Right False
 			Right status -> Right $ isDirectory status
 	| otherwise = do
-		ps <- sshOptions (host, Nothing) (ddarRepoConfig ddarrepo) []
+		ps <- sshOptions NoConsumeStdin (host, Nothing)
+			(ddarRepoConfig ddarrepo) []
 		exitCode <- liftIO $ safeSystem "ssh" (ps ++ params)
 		case exitCode of
 			ExitSuccess -> return $ Right True
@@ -178,7 +180,7 @@ ddarDirectoryExists ddarrepo
 {- Use "ddar t" to determine if a given key is present in a ddar archive -}
 inDdarManifest :: DdarRepo -> Key -> Annex (Either String Bool)
 inDdarManifest ddarrepo k = do
-	(cmd, params) <- ddarRemoteCall ddarrepo 't' []
+	(cmd, params) <- ddarRemoteCall NoConsumeStdin ddarrepo 't' []
 	let p = proc cmd $ toCommand params
 	liftIO $ catchMsgIO $ withHandle StdoutHandle createProcessSuccess p $ \h -> do
 		contents <- hGetContents h