#399

backend/app/services/post_import_previewer.rb

@@ -26,6 +26,12 @@ class PostImportPreviewer
       should_fetch = fetch_metadata == true || fetch_metadata.to_i == row[:source_row].to_i
       metadata, fetch_warnings = metadata_for(url, should_fetch, metadata_cache, fetch_warnings)
       metadata.each do |field, value|
+        if field == 'tags' && provenance[field] != 'manual'
+          previous_origin = provenance[field]
+          attributes[field] = [attributes[field], value].compact.join(' ').split.uniq.join(' ')
+          provenance[field] = previous_origin == 'automatic' ? 'automatic' : previous_origin
+          next
+        end
         next unless provenance[field] == 'automatic' || attributes[field].blank?
 
         attributes[field] = value