simple transfer queue display cleanup

Don't display redundant queued downloads. The only problem with this is
that it reduces the total number of queued transfers the webapp displays.

Assistant/WebApp/DashBoard.hs

@@ -45,7 +45,7 @@ transfersDisplay warnNoScript = do
 	queued <- liftIO $ getTransferQueue $ transferQueue webapp
 	let ident = "transfers"
 	autoUpdate ident NotifierTransfersR (10 :: Int) (10 :: Int)
-	let transfers = current ++ queued
+	let transfers = simplifyTransfers $ current ++ queued
 	if null transfers
 		then ifM (lift $ showIntro <$> getWebAppState)
 			( introDisplay ident
@@ -56,6 +56,16 @@ transfersDisplay warnNoScript = do
 		isrunning info = not $
 			transferPaused info || isNothing (startedTime info)
 
+{- Simplifies a list of transfers, avoiding display of redundant downloads,
+ - that appear immediately after a download of the same key. -}
+simplifyTransfers :: [(Transfer, TransferInfo)] -> [(Transfer, TransferInfo)]
+simplifyTransfers [] = []
+simplifyTransfers (x:[]) = [x]
+simplifyTransfers (v@(t1, _):r@((t2, _):l))
+	| transferDirection t1 == Download && transferDirection t2 == Download &&
+	  transferKey t1 == transferKey t2 = simplifyTransfers (v:l)
+	| otherwise = v : (simplifyTransfers r)
+
 {- Called by client to get a display of currently in process transfers.
  -
  - Returns a div, which will be inserted into the calling page.

doc/design/assistant/syncing.mdwn

@@ -3,15 +3,6 @@ all the other git clones, at both the git level and the key/value level.
 
 ## immediate action items
 
-* The TransferScanner queues downloads for a single file from every remote 
-  that has it. It'd be nicer
-  to only show one queued transfer. Perhaps only queue one, and check
-  for other locations if it fails? Or change the queue so each transfer is
-  really a list of equivilant transfers.
-* Sometimes a Download gets queued from a slow remote, and then a fast
-  remote becomes available, and a Download is queued from it. Would be
-  good to sort the transfer queue to run fast Downloads (and Uploads) first.
-  Or, solve this along with the item above?
 * Ensure that when a remote receives content, and updates its location log,
   it syncs that update back out. Prerequisite for:
 * After git sync, identify new content that we don't have that is now available