assistant: update export db after mergeing git-annex branch changes

Needed so that the assistant can download from exports.
updateExportTreeFromLog is normally only run one time, but needs to be
run repeatedly during the lifetime of the assistant.

This commit was sponsored by Ethan Aubin on Patreon.

Assistant/Threads/Merger.hs

@@ -10,6 +10,7 @@ module Assistant.Threads.Merger where
 import Assistant.Common
 import Assistant.TransferQueue
 import Assistant.BranchChange
+import Assistant.Sync
 import Utility.DirWatcher
 import Utility.DirWatcher.Types
 import qualified Annex.Branch
@@ -62,7 +63,8 @@ onChange file
 	| isAnnexBranch file = do
 		branchChanged
 		diverged <- liftAnnex Annex.Branch.forceUpdate
-		when diverged $
+		when diverged $ do
+			updateExportTreeFromLogAll
 			queueDeferredDownloads "retrying deferred download" Later
 	| otherwise = mergecurrent
   where