execute remote.<name>.annex-shell on remote, if set

It is useful to be able to specify an alternative git-annex-shell
program to execute on the remote, e.g., to run a version not on the
PATH.  Use remote.<name>.annex-shell if specified, instead of the
default "git-annex-shell" i.e., first so-named executable on the
PATH.

Command/Map.hs

@@ -22,6 +22,7 @@ import Logs.UUID
 import Logs.Trust
 import qualified Remote.Helper.Ssh as Ssh
 import qualified Utility.Dot as Dot
+import Types.GitConfig
 
 -- a link from the first repository to the second (its remote)
 data Link = Link Git.Repo Git.Repo
@@ -203,7 +204,9 @@ tryScan r
 
 	configlist = Ssh.onRemote r (pipedconfig, Nothing) "configlist" [] []
 	manualconfiglist = do
-		sshparams <- Ssh.toRepo r [Param sshcmd]
+		g <- fromRepo id
+		let c = extractRemoteGitConfig g (Git.repoDescribe r)
+		sshparams <- Ssh.toRepo r c [Param sshcmd]
 		liftIO $ pipedconfig "ssh" sshparams
 	  where
 		sshcmd = cddir ++ " && " ++