Fix img alt attribute generation when using Sprockets >= 3.0

actionview/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Fix stripping the digest from the automatically generated img tag alt
+    attribute when assets are handled by Sprockets >=3.0.
+
+    *Bart de Water*
+
 *   Create a new `ActiveSupport::SafeBuffer` instance when `content_for` is flushed.
 
     Fixes #19890

actionview/lib/action_view/helpers/asset_tag_helper.rb

@@ -239,7 +239,7 @@ def image_tag(source, options={})
       #   image_alt('underscored_file_name.png')
       #   # => Underscored file name
       def image_alt(src)
-        File.basename(src, '.*'.freeze).sub(/-[[:xdigit:]]{32}\z/, ''.freeze).tr('-_'.freeze, ' '.freeze).capitalize
+        File.basename(src, '.*'.freeze).sub(/-[[:xdigit:]]{32,64}\z/, ''.freeze).tr('-_'.freeze, ' '.freeze).capitalize
       end
 
       # Returns an HTML video tag for the +sources+. If +sources+ is a string,