improve seo tagging, update nginx config file

app/models/post.rb

@@ -121,7 +121,7 @@ class Post < ActiveRecord::Base
     end
 
     def seo_tags
-      @seo_tags ||= humanized_essential_tag_string.gsub(/[^a-z0-9]+/, "-").gsub(/(^-+)|(-+$)/, "")
+      @seo_tags ||= humanized_essential_tag_string.gsub(/[^a-z0-9]+/, "-").gsub(/(?:^-+)|(?:-+$)/, "").gsub(/-{2,}/, "-")
     end
 
     def preview_file_url

config/danbooru_default_config.rb

@@ -396,6 +396,7 @@ module Danbooru
     def addthis_key
     end
 
+    # include essential tags in image urls (requires nginx/apache rewrites)
     def enable_seo_post_urls
       false
     end

script/install/nginx.danbooru.conf

@@ -14,11 +14,17 @@ server {
     expires max;
     break;
   }
+  #location /ssd {
+  #  rewrite ^/ssd(.*)$ $1;
+  #}
   location /data {
-    valid_referers none __hostname__;
+    # if you want to block hotlinking
+    # valid_referers none __hostname__ ~\.google\. ~\.bing\. ~\.yahoo\.;
     if ($invalid_referer) {
       return 403;
     }
+    rewrite ^/data/sample/--.+?--(.+) /data/sample/$1 last;
+    rewrite ^/data/--.+?--(.+) /data/$1 last;
     expires max;
     break;
   }