implement annex.retry et al

Added annex.retry, annex.retry-delay, and per-remote versions to configure
transfer retries.

This commit was supported by the NSF-funded DataLad project.

Command/AddUrl.hs

@@ -339,7 +339,7 @@ downloadWith' downloader dummykey u url afile =
 	checkDiskSpaceToGet dummykey Nothing $ do
 		tmp <- fromRepo $ gitAnnexTmpObjectLocation dummykey
 		ok <- Transfer.notifyTransfer Transfer.Download url $
-			Transfer.download u dummykey afile Transfer.forwardRetry $ \p -> do
+			Transfer.download u dummykey afile Transfer.stdRetry $ \p -> do
 				liftIO $ createDirectoryIfMissing True (parentDir tmp)
 				downloader tmp p
 		if ok

Command/Export.hs

@@ -216,6 +216,8 @@ performExport r ea db ek af contentsha loc = do
 	sent <- case ek of
 		AnnexKey k -> ifM (inAnnex k)
 			( notifyTransfer Upload af $
+				-- Using noRetry here because interrupted
+				-- exports cannot be resumed.
 				upload (uuid r) k af noRetry $ \pm -> do
 					let rollback = void $
 						performUnexport r ea db [ek] loc

Command/Get.hs

@@ -110,7 +110,7 @@ getKey' key afile = dispatch
 			either (const False) id <$> Remote.hasKey r key
 		| otherwise = return True
 	docopy r witness = getViaTmp (RemoteVerify r) key $ \dest ->
-		download (Remote.uuid r) key afile forwardRetry
+		download (Remote.uuid r) key afile stdRetry
 			(\p -> do
 				showAction $ "from " ++ Remote.name r
 				Remote.retrieveKeyFile r key afile dest p

Command/Move.hs

@@ -134,7 +134,7 @@ toPerform dest move key afile fastcheck isthere =
 		Right False -> do
 			showAction $ "to " ++ Remote.name dest
 			ok <- notifyTransfer Upload afile $
-				upload (Remote.uuid dest) key afile forwardRetry $
+				upload (Remote.uuid dest) key afile stdRetry $
 					Remote.storeKey dest key afile
 			if ok
 				then finish $
@@ -199,7 +199,7 @@ fromPerform src move key afile = do
 		)
   where
 	go = notifyTransfer Download afile $ 
-		download (Remote.uuid src) key afile forwardRetry $ \p ->
+		download (Remote.uuid src) key afile stdRetry $ \p ->
 			getViaTmp (RemoteVerify src) key $ \t ->
 				Remote.retrieveKeyFile src key afile t p
 	dispatch _ False = stop -- failed

Command/TransferKey.hs

@@ -51,7 +51,7 @@ start o key = case fromToOptions o of
 
 toPerform :: Key -> AssociatedFile -> Remote -> CommandPerform
 toPerform key file remote = go Upload file $
-	upload (uuid remote) key file forwardRetry $ \p -> do
+	upload (uuid remote) key file stdRetry $ \p -> do
 		ok <- Remote.storeKey remote key file p
 		when ok $
 			Remote.logStatus remote key InfoPresent
@@ -59,7 +59,7 @@ toPerform key file remote = go Upload file $
 
 fromPerform :: Key -> AssociatedFile -> Remote -> CommandPerform
 fromPerform key file remote = go Upload file $
-	download (uuid remote) key file forwardRetry $ \p ->
+	download (uuid remote) key file stdRetry $ \p ->
 		getViaTmp (RemoteVerify remote) key $ 
 			\t -> Remote.retrieveKeyFile remote key file t p
 

Command/TransferKeys.hs

@@ -35,13 +35,13 @@ start = do
   where
 	runner (TransferRequest direction remote key file)
 		| direction == Upload = notifyTransfer direction file $
-			upload (Remote.uuid remote) key file forwardRetry $ \p -> do
+			upload (Remote.uuid remote) key file stdRetry $ \p -> do
 				ok <- Remote.storeKey remote key file p
 				when ok $
 					Remote.logStatus remote key InfoPresent
 				return ok
 		| otherwise = notifyTransfer direction file $
-			download (Remote.uuid remote) key file forwardRetry $ \p ->
+			download (Remote.uuid remote) key file stdRetry $ \p ->
 				getViaTmp (RemoteVerify remote) key $ \t -> do
 					r <- Remote.retrieveKeyFile remote key file t p
 					-- Make sure we get the current