avoid interleaving command stages with Concurrency 1

Before, -J1 was different than no -J: It makes concurrent-output be used
for display, and it actually can run concurrent jobs in some situations.
Eg, a perform stage and a cleanup stage can both run.

dupState is used in several places, and changes NonConcurrent to
Concurrent 1. My concern is that this might, in some case, enable
that concurrent behavior. And in particular, that it might get enabled in
--batch mode, when the user is not expecting concurrent output because
they did not pass -J.

While I don't have a test case where that happens and causes out of
order output, it looks like it could, and so prudent to make this change.

CmdLine/Action.hs

@@ -55,7 +55,9 @@ commandActions = mapM_ commandAction
 commandAction :: CommandStart -> Annex ()
 commandAction start = getConcurrency >>= \case
 	NonConcurrent -> runnonconcurrent
-	Concurrent _ -> runconcurrent
+	Concurrent n
+		| n > 1 -> runconcurrent
+		| otherwise -> runnonconcurrent
 	ConcurrentPerCpu -> runconcurrent
   where
 	runnonconcurrent = void $ includeCommandAction start