sync content with import remotes

This didn't used to be needed because importKeys would import all
content and so doing another pass was redundant.

But since 40017089f2 it uses
importChanges, so only new files are imported. If a file that was
already imported before was dropped, that would prevent sync --content
from gettng its content again.

Sponsored-by: Jack Hill on Patreon

Command/Sync.hs

@@ -295,13 +295,16 @@ seek' o = do
 					seekExportContent (Just o)
 						(filter isExport contentremotes)
 
-				-- Sync content with remotes, but not with
-				-- export or import remotes, which handle content
-				-- syncing as part of export and import.
+				-- Sync content with remotes, including
+				-- with import remotes (since importing
+				-- only downloads new files not old files),
+				-- but not with export only remotes.
+				let shouldsynccontent r
+					| isExport r && not (isImport r) = False
+					| otherwise = True
 				syncedcontent <- withbranch $
-					seekSyncContent o $ filter
-						(\r -> not (isExport r || isImport r))
-						contentremotes
+					seekSyncContent o
+						(filter shouldsynccontent contentremotes)
 
 				-- Transferring content can take a while,
 				-- and other changes can be pushed to the