Escape metacharacters in non-whole-word keyword mutes. Fixes #533.

Also addresses #463.

app/models/glitch/keyword_mute.rb

@@ -50,7 +50,7 @@ class Glitch::KeywordMute < ApplicationRecord
     end
 
     def matches?(str)
-      str =~ (whole_word ? boundary_regex_for_keyword : /#{keyword}/i)
+      str =~ (whole_word ? boundary_regex_for_keyword : /#{Regexp.escape(keyword)}/i)
     end
   end
 

spec/models/glitch/keyword_mute_spec.rb

@@ -79,12 +79,18 @@ RSpec.describe Glitch::KeywordMute, type: :model do
         expect(matcher.matches?('(hot take)')).to be_truthy
       end
 
-      it 'escapes metacharacters in keywords' do
+      it 'escapes metacharacters in whole-word keywords' do
         Glitch::KeywordMute.create!(account: alice, keyword: '(hot take)')
 
         expect(matcher.matches?('(hot take)')).to be_truthy
       end
 
+      it 'escapes metacharacters in non-whole-word keywords' do
+        Glitch::KeywordMute.create!(account: alice, keyword: '(-', whole_word: false)
+
+        expect(matcher.matches?('bad (-)')).to be_truthy
+      end
+
       it 'uses case-folding rules appropriate for more than just English' do
         Glitch::KeywordMute.create!(account: alice, keyword: 'großeltern')