Merge branch 'master' into mrbrdo-fixserialization

* master: (142 commits)
  Use Colspan in th Tags
  Added test for link_to_unless to make sure the result consistency.
  Escape the string even when the condition of link_to_unless is not satisfied.
  Add CHANGELOG entry for #10969
  Use a case insensitive URI Regexp for #asset_path
  collection tags accept html attributes as the last element of collection
  Rewind StringIO instances before be parsed again
  Use xml instead already parsed xml
  Updated the doc for const_regexp [ci skip]
  Make test name descriptive and add reference to original regression commit
  fixture setup does not rely on `AR::Base.configurations`.
  regression test + mysql2 adapter raises correct error if conn is closed.
  cleanup, remove trailing whitespace from AR changelog
  'json' gem is no more required under JRuby
  fix typos
  Fix AS changelog [ci skip]
  Update the HTML boolean attributes per the HTML 5.1 spec
  Changing const_regexp to check for constant name.
  valid_app_const? -> valid_const?
  Add CHANGELOG entry for #10740
  ...

1 files changed, 10 insertions, 1 deletions

diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 456abaf612..1e196b0e42 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -104,6 +104,15 @@ This method generates a cache key that depends on all products and can be used i
   All available products:
 <% end %>
 ```
+
+If you want to cache a fragment under certain condition you can use `cache_if` or `cache_unless` 
+
+```erb
+<% cache_if (condition, cache_key_for_products) do %>
+  All available products:
+<% end %>
+```
+
 You can also use an Active Record model as the cache key:
 
 ```erb
@@ -236,7 +245,7 @@ config.cache_store = :ehcache_store
 
 When initializing the cache, you may use the `:ehcache_config` option to specify the Ehcache config file to use (where the default is "ehcache.xml" in your Rails config directory), and the :cache_name option to provide a custom name for your cache (the default is rails_cache).
 
-In addition to the standard `:expires_in` option, the `write` method on this cache can also accept the additional  `:unless_exist` option, which will cause the cache store to use Ehcache's `putIfAbsent` method instead of `put`, and therefore will not overwrite an existing entry. Additionally, the `write` method supports all of the properties exposed by the [Ehcache Element class](http://ehcache.org/apidocs/net/sf/ehcache/Element.html) , including:
+In addition to the standard `:expires_in` option, the `write` method on this cache can also accept the additional `:unless_exist` option, which will cause the cache store to use Ehcache's `putIfAbsent` method instead of `put`, and therefore will not overwrite an existing entry. Additionally, the `write` method supports all of the properties exposed by the [Ehcache Element class](http://ehcache.org/apidocs/net/sf/ehcache/Element.html) , including:
 
 | Property                    | Argument Type       | Description                                                 |
 | --------------------------- | ------------------- | ----------------------------------------------------------- |