Fix #5194: AND/OR no longer trigger autocomplete.

Also change the /autocomplete.json API to no longer strip '-' and '~'
from the start of the tag. This may be a breaking change if third-party
scripts relied on this behavior.

test/functional/autocomplete_controller_test.rb

@@ -16,6 +16,8 @@ class AutocompleteControllerTest < ActionDispatch::IntegrationTest
     context "index action" do
       setup do
         create(:tag, name: "azur_lane")
+        create(:tag, name: "android")
+        create(:tag, name: "original")
       end
 
       should "work for opensearch queries" do
@@ -27,8 +29,6 @@ class AutocompleteControllerTest < ActionDispatch::IntegrationTest
 
       should "work for tag queries" do
         assert_autocomplete_equals(["azur_lane"], "azur", "tag_query")
-        assert_autocomplete_equals(["azur_lane"], "-azur", "tag_query")
-        assert_autocomplete_equals(["azur_lane"], "~azur", "tag_query")
         assert_autocomplete_equals(["azur_lane"], "AZUR", "tag_query")
 
         assert_autocomplete_equals(["rating:sensitive"], "rating:s", "tag_query")
@@ -42,6 +42,11 @@ class AutocompleteControllerTest < ActionDispatch::IntegrationTest
         assert_equal([], response.parsed_body)
       end
 
+      should "work for the AND and OR keywords" do
+        assert_autocomplete_equals(["android"], "and", "tag_query")
+        assert_autocomplete_equals(["original"], "or", "tag_query")
+      end
+
       should "not set session cookies when the response is publicly cached" do
         get autocomplete_index_path(search: { query: "azur", type: "tag_query" }), as: :json