extend Git.Queue to be able to queue more than simple git commands

While I was in there, I noticed and fixed a bug in the queue size
calculations. It was never encountered only because Queue.add was
only ever run with 1 file in the list.

Command/Add.hs

@@ -121,5 +121,5 @@ cleanup file key hascontent = do
 		( return [Param "-f"]
 		, return []
 		)
-	Annex.Queue.add "add" (params++[Param "--"]) [file]
+	Annex.Queue.addCommand "add" (params++[Param "--"]) [file]
 	return True

Command/Fix.hs

@@ -36,5 +36,5 @@ perform file link = do
 
 cleanup :: FilePath -> CommandCleanup
 cleanup file = do
-	Annex.Queue.add "add" [Param "--force", Param "--"] [file]
+	Annex.Queue.addCommand "add" [Param "--force", Param "--"] [file]
 	return True

Command/FromKey.hs

@@ -39,5 +39,5 @@ perform key file = do
 
 cleanup :: FilePath -> CommandCleanup
 cleanup file = do
-	Annex.Queue.add "add" [Param "--"] [file]
+	Annex.Queue.addCommand "add" [Param "--"] [file]
 	return True

Command/Fsck.hs

@@ -155,7 +155,7 @@ fixLink key file = do
 		liftIO $ createDirectoryIfMissing True (parentDir file)
 		liftIO $ removeFile file
 		liftIO $ createSymbolicLink want file
-		Annex.Queue.add "add" [Param "--force", Param "--"] [file]
+		Annex.Queue.addCommand "add" [Param "--force", Param "--"] [file]
 	return True
 
 {- Checks that the location log reflects the current status of the key,

Command/Lock.hs

@@ -24,5 +24,5 @@ start file = do
 
 perform :: FilePath -> CommandPerform
 perform file = do
-	Annex.Queue.add "checkout" [Param "--"] [file]
+	Annex.Queue.addCommand "checkout" [Param "--"] [file]
 	next $ return True -- no cleanup needed