Bug: in some cases searching for multiple metatags would cause one
metatag to be ignored. For example, a search for {{user:1 pool:2}} would
be treated as a search for {{pool:2}}.
Cause: we used `ActiveRecord::Relation#merge` to combine two relations,
which was wrong because `merge` doesn't combine `column IN (?)` clauses
correctly. If there are two `column IN (?)` clauses on the same column,
then `#merge` takes only the second clause and ignores the first.
Fix: write our own half-baked `#and` method to work around Rails'
broken-by-design `#merge` method.
ref: https://github.com/rails/rails/issues/33501.
* Fix not being able to use the status: metatag twice in the same search.
* Fix status:active excluding banned posts.
* Fix status:garbage returning all posts.
Support using the same numeric-valued metatag twice in the same search.
Numeric-valued metatags are those taking an integer, float, filesize, or
date argument. Previously using the same metatag twice would cause the
second metatag to overwrite the first metatag.
Examples:
* "id:>5 id:<10"
* "width:>500 width:<1000"
* "date:>2019-01-01 date:<2020-01-01"
Partial fix for #4389.
* Fix invalid username searches returning all posts instead of no posts.
* Fix "user:A user:B" returning results for user:B instead of no results.
* Fix "approver:A approver:B" returning results for approver:B instead of no results.
* Add support for negated -commenter, -noter, -noteupdater, -upvote, -downvote metatags.
* Add support for "any" and "none" values for all username metatags,
including negated metatags that didn't support "any" or "none" before.
* Change noter:any and commenter:any to include posts with deleted notes
or comments. Note that commenter:<username> already included deleted
comments before. This is so that commenter:any has the same behavior
as commenter:<username>
