tags/index: don't show aliases when search matches primary tag.

When searching e.g. "*mask*", don't show "surgical_mask <- medical_mask"
because "*mask*" already matches the primary tag.

app/helpers/tags_helper.rb

@@ -3,4 +3,12 @@ module TagsHelper
     return nil if tag.blank?
     "tag-type-#{tag.category}"
   end
+
+  def tag_alias_for_pattern(tag, pattern)
+    return nil if pattern.blank?
+
+    tag.consequent_aliases.find do |tag_alias|
+      !tag.name.ilike?(pattern) && tag_alias.antecedent_name.ilike?(pattern)
+    end
+  end
 end