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/WebApp/Utility.hs

@@ -135,9 +135,10 @@ startTransfer t = do
 			let st = fromJust $ threadState webapp
 			let dstatus = daemonStatus webapp
 			let slots = transferSlots webapp
+			let commitchan = commitChan webapp
 			liftIO $ inImmediateTransferSlot dstatus slots $ do
 				program <- readProgramFile
-				Transferrer.startTransfer st dstatus program t info
+				Transferrer.startTransfer st dstatus commitchan program t info
 
 getCurrentTransfers :: Handler TransferMap
 getCurrentTransfers = currentTransfers