Add ActiveModel::Errors#merge!

ActiveModel::Errors#merge! allows ActiveModel::Errors to append errors from
a separate ActiveModel::Errors instance onto their own.

Example:

    person = Person.new
    person.errors.add(:name, :blank)

    errors = ActiveModel::Errors.new(Person.new)
    errors.add(:name, :invalid)

    person.errors.merge!(errors)
    puts person.errors.messages
    # => { name: ["can't be blank", "is invalid"] }

1 files changed, 4 insertions, 0 deletions

diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 2916e5eabb..048c43f2c4 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Add method `#merge!` for `ActiveModel::Errors`.
+
+    *Jahfer Husain*
+
 *   Fix regression in numericality validator when comparing Decimal and Float input
     values with more scale than the schema.