I recently started moving away from Picasa to Photos. I set up a Hazel rule to import photos from my main photo directory on my iMac. I set it up as follows: Date Last Modified is after Date Last Matched, Import into Photos "Album".
The photos directory it is pointing to is updated from my server - a separate process copies new pictures into this folder as they become available.
I am constantly being presented with duplicate photo import messages within Photos so something is not going according to plan.
I did a search of the forum but could only find some older posts related to iPhoto. I am happy to provide further information to help diagnose this. Thanks.