Change Details

wpExistingTags is not passed in the request at Special:EditTags if multiple revisions are selected. It follows that the option to remove all tags cannot work. Also, users are prompted to add/remove tags that they cannot add/remove. I think we should check beforehand and only propose them tags they can add/remove. I had done this in [[https://gerrit.wikimedia.org/r/#/c/201905/|commit 201905]] but will split it off since it's not related to the main issue of that commit.