change retrieveExportWithContentIdentifier to take a list of ContentIdentifier

This partly fixes an issue where there are duplicate files in the
special remote, and the first file gets swapped with another duplicate,
or deleted. The swap case is fixed by this, the deleted case will need
other changes.

This makes retrieveExportWithContentIdentifier take a list of allowed
ContentIdentifier, same as storeExportWithContentIdentifier,
removeExportWithContentIdentifier, and
checkPresentExportWithContentIdentifier.

Of the special remotes that support importtree, borg is a special case
and does not use content identifiers, S3 I assume can't get mixed up
like this, directory certainly has the problem, and adb also appears to
have had the problem.

Sponsored-by: Graham Spencer on Patreon

Remote/S3.hs

@@ -649,8 +649,8 @@ mkImportableContentsVersioned info = build . groupfiles
 		| otherwise =
 			i : removemostrecent mtime rest
 
-retrieveExportWithContentIdentifierS3 :: S3HandleVar -> Remote -> RemoteStateHandle -> S3Info -> ExportLocation -> ContentIdentifier -> FilePath -> Either Key (Annex Key) -> MeterUpdate -> Annex (Key, Verification)
-retrieveExportWithContentIdentifierS3 hv r rs info loc cid dest gk p =
+retrieveExportWithContentIdentifierS3 :: S3HandleVar -> Remote -> RemoteStateHandle -> S3Info -> ExportLocation -> [ContentIdentifier] -> FilePath -> Either Key (Annex Key) -> MeterUpdate -> Annex (Key, Verification)
+retrieveExportWithContentIdentifierS3 hv r rs info loc (cid:_) dest gk p =
 	case gk of
 		Right _mkkey -> do
 			k <- go Nothing
@@ -675,6 +675,7 @@ retrieveExportWithContentIdentifierS3 hv r rs info loc cid dest gk p =
 			return k
 		Nothing -> giveup $ needS3Creds (uuid r)
 	o = T.pack $ bucketExportLocation info loc
+retrieveExportWithContentIdentifierS3 _ _ _ _ _ [] _ _ _ = giveup "missing content identifier"
 
 {- Catch exception getObject returns when a precondition is not met,
  - and replace with a more understandable message for the user. -}