Skip already downloaded LFS objects in mirror updates
Previously in Projects::UpdateMirrorService#update_lfs_objects
(https://gitlab.com/gitlab-org/gitlab/blob/c4604fbd988ac6da7afe693cf1759c7bf593a5a8/ee/app/services/projects/update_mirror_service.rb#L43), all LFS files are redownloaded from the mirror site even if they have already been imported. This would lead to unnecessary HTTPS traffic between the
upstream mirror and GitLab.
We now filter out OIDs that have already been linked to the project.
Relates to #336047 (closed)
Edited by Stan Hu