ensure that git-annex branch is pushed after a successful transfer

I now have this topology working:

   assistant ---> {bare repo, special remote} <--- assistant

And, I think, also this one:

        +----------- bare repo --------+
        v                              v
  assistant ---> special remote <--- assistant

While before with assistant <---> assistant connections, both sides got
location info updated after a transfer, in this topology, the bare repo
*might* get its location info updated, but the other assistant has no way to
know that it did. And a special remote doesn't record location info,
so transfers to it won't propigate out location log changes at all.

So, for these to work, after a transfer succeeds, the git-annex branch
needs to be pushed. This is done by recording a synthetic commit has
occurred, which lets the pusher handle pushing out the change (which will
include actually committing any still journalled changes to the git-annex
branch).

Of course, this means rather a lot more syncing action than happened
before. At least the pusher bundles together very close together pushes,
somewhat. Currently it just waits 2 seconds between each push.

Assistant/Threads/Pusher.hs

@@ -49,12 +49,12 @@ pushThread st dstatus commitchan pushmap pushnotifier = thread $ runEvery (Secon
 	-- Next, wait until at least one commit has been made
 	commits <- getCommits commitchan
 	-- Now see if now's a good time to push.
-	now <- getCurrentTime
-	if shouldPush now commits
+	if shouldPush commits
 		then do
 			remotes <- filter pushable . syncRemotes
 				<$> getDaemonStatus dstatus
-			unless (null remotes) $ 
+			unless (null remotes) $ do
+				now <- getCurrentTime
 				void $ alertWhile dstatus (pushAlert remotes) $
 					pushToRemotes thisThread now st (Just pushnotifier) (Just pushmap) remotes
 		else do
@@ -77,7 +77,7 @@ pushThread st dstatus commitchan pushmap pushnotifier = thread $ runEvery (Secon
  - already determines batches of changes, so we can't easily determine
  - batches better.
  -}
-shouldPush :: UTCTime -> [Commit] -> Bool
-shouldPush _now commits
+shouldPush :: [Commit] -> Bool
+shouldPush commits
 	| not (null commits) = True
 	| otherwise = False