Don't include ellipsis in truncated digest output

Using `truncate` to limit the length of the digest has the unwanted side
effect of adding an ellipsis when the input is longer than the limit.

Also:
 - Don't instantiate a new object for every digest
 - Rename the configuration option to `hash_digest_class`
 - Update the CHANGELOG entry to describe how to use the feature

1 files changed, 2 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index 3488721df9..91872e29c8 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -68,9 +68,9 @@ module ActiveSupport
     end
 
     initializer "active_support.set_hash_digest_class" do |app|
-      if app.config.active_support.respond_to?(:use_hash_digest_class) && app.config.active_support.use_hash_digest_class
+      if app.config.active_support.respond_to?(:hash_digest_class) && app.config.active_support.hash_digest_class
         ActiveSupport::Digest.hash_digest_class =
-          app.config.active_support.use_hash_digest_class
+          app.config.active_support.hash_digest_class
       end
     end
   end