Use %{} syntax in I18n (faster) instead of {{}}.

actionpack/lib/action_view/helpers/form_helper.rb

@@ -1165,13 +1165,13 @@ def hidden_field(method, options = {})
       # submit button label, otherwise, it uses "Update Post".
       #
       # Those labels can be customized using I18n, under the helpers.submit key and accept
-      # the {{model}} as translation interpolation:
+      # the %{model} as translation interpolation:
       #
       #   en:
       #     helpers:
       #       submit:
-      #         create: "Create a {{model}}"
-      #         update: "Confirm changes to {{model}}"
+      #         create: "Create a %{model}"
+      #         update: "Confirm changes to %{model}"
       #
       # It also searches for a key specific for the given object:
       #

actionpack/lib/action_view/locale/en.yml

@@ -102,37 +102,37 @@
       half_a_minute: "half a minute"
       less_than_x_seconds:
         one:   "less than 1 second"
-        other: "less than {{count}} seconds"
+        other: "less than %{count} seconds"
       x_seconds:
         one:   "1 second"
-        other: "{{count}} seconds"
+        other: "%{count} seconds"
       less_than_x_minutes:
         one:   "less than a minute"
-        other: "less than {{count}} minutes"
+        other: "less than %{count} minutes"
       x_minutes:
         one:   "1 minute"
-        other: "{{count}} minutes"
+        other: "%{count} minutes"
       about_x_hours:
         one:   "about 1 hour"
-        other: "about {{count}} hours"
+        other: "about %{count} hours"
       x_days:
         one:   "1 day"
-        other: "{{count}} days"
+        other: "%{count} days"
       about_x_months:
         one:   "about 1 month"
-        other: "about {{count}} months"
+        other: "about %{count} months"
       x_months:
         one:   "1 month"
-        other: "{{count}} months"
+        other: "%{count} months"
       about_x_years:
         one:   "about 1 year"
-        other: "about {{count}} years"
+        other: "about %{count} years"
       over_x_years:
         one:   "over 1 year"
-        other: "over {{count}} years"
+        other: "over %{count} years"
       almost_x_years:
         one:   "almost 1 year"
-        other: "almost {{count}} years"
+        other: "almost %{count} years"
     prompts:
       year:   "Year"
       month:  "Month"
@@ -148,7 +148,7 @@
 
     # Default translation keys for submit FormHelper
     submit:
-      create: 'Create {{model}}'
-      update: 'Update {{model}}'
-      submit: 'Save {{model}}'
+      create: 'Create %{model}'
+      update: 'Update %{model}'
+      submit: 'Save %{model}'
 

activemodel/lib/active_model/errors.rb

@@ -223,7 +223,7 @@ def full_messages
         else
           attr_name = attribute.to_s.gsub('.', '_').humanize
           attr_name = @base.class.human_attribute_name(attribute, :default => attr_name)
-          options = { :default => "{{attribute}} {{message}}", :attribute => attr_name }
+          options = { :default => "%{attribute} %{message}", :attribute => attr_name }
 
           messages.each do |m|
             full_messages << I18n.t(:"errors.format", options.merge(:message => m))

activemodel/lib/active_model/locale/en.yml

 en:
   errors:
     # The default format use in full error messages.
-    format: "{{attribute}} {{message}}"
+    format: "%{attribute} %{message}"
 
     # The values :model, :attribute and :value are always available for interpolation
     # The value :count is available when applicable. Can be used for pluralization.
@@ -13,15 +13,15 @@ en:
       accepted: "must be accepted"
       empty: "can't be empty"
       blank: "can't be blank"
-      too_long: "is too long (maximum is {{count}} characters)"
-      too_short: "is too short (minimum is {{count}} characters)"
-      wrong_length: "is the wrong length (should be {{count}} characters)"
+      too_long: "is too long (maximum is %{count} characters)"
+      too_short: "is too short (minimum is %{count} characters)"
+      wrong_length: "is the wrong length (should be %{count} characters)"
       not_a_number: "is not a number"
       not_an_integer: "must be an integer"
-      greater_than: "must be greater than {{count}}"
-      greater_than_or_equal_to: "must be greater than or equal to {{count}}"
-      equal_to: "must be equal to {{count}}"
-      less_than: "must be less than {{count}}"
-      less_than_or_equal_to: "must be less than or equal to {{count}}"
+      greater_than: "must be greater than %{count}"
+      greater_than_or_equal_to: "must be greater than or equal to %{count}"
+      equal_to: "must be equal to %{count}"
+      less_than: "must be less than %{count}"
+      less_than_or_equal_to: "must be less than or equal to %{count}"
       odd: "must be odd"
       even: "must be even"

activerecord/lib/active_record/locale/en.yml

@@ -9,7 +9,7 @@ en:
     errors:
       messages:
         taken: "has already been taken"
-        record_invalid: "Validation failed: {{errors}}"
+        record_invalid: "Validation failed: %{errors}"
         # Append your own errors here or at the model/attributes scope.
 
       # You can define own errors for models or model attributes.
@@ -18,7 +18,7 @@ en:
       # For example,
       #   models:
       #     user:
-      #       blank: "This is a custom blank message for {{model}}: {{attribute}}"
+      #       blank: "This is a custom blank message for %{model}: %{attribute}"
       #       attributes:
       #         login:
       #           blank: "This is a custom blank message for User login"