S3: Avoid writing or checking the uuid file in the S3 bucket when importtree=yes or exporttree=yes

It does not make sense for either; importing from an existing bucket should
not write to it. And the user may not have write access at all. And exporting to
a bucket should not write other files.

Also this prevents the uuid file being imported after being written.

Sponsored-by: Dartmouth College's DANDI project

CHANGELOG

@@ -15,6 +15,8 @@ git-annex (10.20220625) UNRELEASED; urgency=medium
     This may need to be enabled for old android devices that used to work
     without it being set, since version 10.20220222 started using 
     find -printf.
+  * S3: Avoid writing or checking the uuid file in the S3 bucket when
+    importtree=yes or exporttree=yes.
 
  -- Joey Hess <id@joeyh.name>  Tue, 28 Jun 2022 14:49:17 -0400
 

Remote/S3.hs

@@ -777,9 +777,11 @@ genBucket c gc u = do
  -
  - Note that IA buckets can only created by having a file
  - stored in them. So this also takes care of that.
+ -
+ - Not done for import/export buckets.
  -}
 writeUUIDFile :: ParsedRemoteConfig -> UUID -> S3Info -> S3Handle -> Annex ()
-writeUUIDFile c u info h = do
+writeUUIDFile c u info h = unless (exportTree c || importTree c) $ do
 	v <- checkUUIDFile c u info h
 	case v of
 		Right True -> noop
@@ -794,15 +796,19 @@ writeUUIDFile c u info h = do
 	mkobject = putObject info file (RequestBodyLBS uuidb)
 
 {- Checks if the UUID file exists in the bucket
- - and has the specified UUID already. -}
+ - and has the specified UUID already.
+ -
+ - Not done for import/export buckets. -}
 checkUUIDFile :: ParsedRemoteConfig -> UUID -> S3Info -> S3Handle -> Annex (Either SomeException Bool)
-checkUUIDFile c u info h = tryNonAsync $ liftIO $ runResourceT $ do
-	resp <- tryS3 $ sendS3Handle h (S3.getObject (bucket info) file)
-	case resp of
-		Left _ -> return False
-		Right r -> do
-			v <- AWS.loadToMemory r
-			extractFromResourceT (check v)
+checkUUIDFile c u info h 
+	| exportTree c || importTree c = pure (Right False)
+	| otherwise = tryNonAsync $ liftIO $ runResourceT $ do
+		resp <- tryS3 $ sendS3Handle h (S3.getObject (bucket info) file)
+		case resp of
+			Left _ -> return False
+			Right r -> do
+				v <- AWS.loadToMemory r
+				extractFromResourceT (check v)
   where
 	check (S3.GetObjectMemoryResponse _meta rsp) =
 		responseStatus rsp == ok200 && responseBody rsp == uuidb