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Changes between Initial Version and Version 4 of Ticket #4895

Ticket #4895
- Property Status changed from new to reopened
- Property Summary changed from Category unions and intersections to Tag unions and intersections

-                      initial
+                      v4
 As was done for categories in #4750, let's add private tag__in, tag__and, and tag__not_in query vars.
+Let's also decide on how to specify intersections and unions in the public query vars. We have tag_id and tag.  tag_id currently takes a single numeric ID, and tag takes a single tag slug.  tag is the var we use when creating links and such.  tag_is isn't exposed anywhere at the moment. I think we can extend tag to allow the use of "+" to request tag intersections and commas to request unions.  Only one or the other can be specified in the same request.
+tag+tag2+tag3
+tag,tag2,tag3