show consitency in cache key and avoid getting into implementation details

actionview/lib/action_view/helpers/cache_helper.rb

@@ -24,7 +24,7 @@ module ActionView
       # This approach will assume that when a new topic is added, you'll touch
       # the project. The cache key generated from this call will be something like:
       #
-      #   views/template/action.html.erb:7a1156131a6928cb0026877f8b749ac9/projects/123
+      #   views/template/action:7a1156131a6928cb0026877f8b749ac9/projects/123
       #         ^template path           ^template tree digest            ^class   ^id
       #
       # This cache key is stable, but it's combined with a cache version derived from the project

guides/source/caching_with_rails.md

@@ -88,20 +88,18 @@ When your application receives its first request to this page, Rails will write
 a new cache entry with a unique key. A key looks something like this:
 
 ```
-views/products/index.html.erb:bea67108094918eeba42cd4a6e786901/products/1
+views/products/index:bea67108094918eeba42cd4a6e786901/products/1
 ```
 
-`products/1` is a stable key but a cache version, derived from the product
-record, is stored in the cache entry. When the product `updated_at` is touched,
-the `cache_version` changes. Rails will check it when pulling the entry from the
-cache and write the new information to the same cache key. This is called recyclable
-key-based expiration.
-
 The string of characters in the middle is a template tree digest. It is a hash
-digest computed based on the contents of the entire template file. If
-you change the template file (e.g., the HTML changes), the digest will change,
+digest computed based on the contents of the view fragment you are caching. If
+you change the view fragment (e.g., the HTML changes), the digest will change,
 expiring the existing file.
 
+A cache version, derived from the product record, is stored in the cache entry.
+When the product is touched, the cache version changes, and any cached fragments
+that contain the previous version are ignored.
+
 TIP: Cache stores like Memcached will automatically delete old cache files.
 
 If you want to cache a fragment under certain conditions, you can use