Q:

Transfer Firebase Storage Bucket between projects

I am attempting to copy the contents of a folder in one Firebase project's Storage bucket to the storage bucket of another Firebase project.
I have been following the firestore docs and this SO question.
Both projects have the necessary permissions to other's service accounts.
Here is what I have done:
When attempting to transfer files from a folder in the default bucket of Project-A to the default bucket of Project-B using the cloud shell terminal, I first set the project to 'Project-A'. I then ran gcloud beta firestore export gs://[PROJECT_A_ID] --collection-ids=[FOLDER_TO_TRANSFER] --async. This succeeds and creates a folder called "2019-08-26T21:23:23_26014/" in Project-A. This folder contains some metadata. 
Next, I tried beginning the import by setting the project to Project-B and running gcloud beta firestore import gs://[PROJECT_A_ID]/2019-08-26T21:23:23_26014
This completes and the logs display this message:
done: true
metadata:
  '@type': type.googleapis.com/google.firestore.admin.v1beta1.ImportDocumentsMetadata
  collectionIds:
  - [FOLDER_TO_TRANSFER]
  endTime: '2019-08-26T21:25:56.794588Z'
  inputUriPrefix: gs://[PROJECT_A_ID]/2019-08-26T21:23:23_26014
  operationState: SUCCESSFUL
  startTime: '2019-08-26T21:25:19.689430Z'
name: projects/[PROJECT_B]/databases/(default)/operations/[SOME_ID_STRING]
response:
  '@type': type.googleapis.com/google.protobuf.Empty
However, the Project-B storage bucket doesn't have any new files or folders. It looks like the import did nothing. Am I missing something?

A:

You can create a transfer job in the GCP Console. You can specify source/destination buckets from different projects as long as you have access permissions. You can specify the folder by setting "Specify file filters":
https://console.cloud.google.com/storage/transfer
You can also use the gsutil tool, which is part of gcloud, to move or copy your objects to another bucket.
So your default buckets would be gs://[PROJECT_A_ID].appspot.com and gs://[PROJECT_B_ID].appspot.com Let's say you wanted to copy over the contents of my_directory:
gsutil cp -r gs://[PROJECT_A_ID].appspot.com/my_directory gs://[PROJECT_B_ID].appspot.com

