I recently started using iCloud Photo Library as a means for sharing photos with other iOS / Mac users. Up until recently I mostly used Google+ for this - I've been auto-uploading photos there for years. I'd like to copy my photos from Google+ into iCloud Photo Library, but I also don't wish to turn off auto-backup on Google+, because A) having a duplicate back-up is a good idea in my opinion, and B) Google+ provides auto-awesome and other cool features.
How can I copy my photos to iCloud but avoid duplicates in Google+ due to auto-backup?
How can I copy my photos to iCloud but avoid duplicates in Google+ due to auto-backup?