fix regexp in reltag toggle

should account for all special characters while preserving newlines

app/assets/javascripts/related_tag.js

@@ -194,7 +194,8 @@
     var tag = $(e.target).html().replace(/ /g, "_").replace(/&gt;/g, ">").replace(/&lt;/g, "<").replace(/&amp;/g, "&");
 
     if ($.inArray(tag, tags) > -1) {
-      $field.val($field.val().replace(new RegExp("\\b" + tag + "\\b", "gi"), " "));
+      var escaped_tag = Danbooru.regexp_escape(tag);
+      $field.val($field.val().replace(new RegExp("(^|\\s)" + escaped_tag + "($|\\s)", "gi"), "$1$2"));
     } else {
       $field.val($field.val() + " " + tag);
     }

app/assets/javascripts/utility.js

@@ -74,6 +74,10 @@
     return filtered;
   }
 
+  Danbooru.regexp_escape = function(string) {
+    return string.replace(/([.?*+^$[\]\\(){}|-])/g, "\\$1");
+  }
+
   $.fn.selectRange = function(start, end) {
     return this.each(function() {
       if (this.setSelectionRange) {