ActionMailer: support overriding template name in multipart

Implicit rendering in multipart blocks now also uses the template
name from the options hash instead of always using the action name.

So you can now write

    mail(template_name: template_name) do |format|
      format.text
      format.html
    end

1 files changed, 5 insertions, 0 deletions

diff --git a/actionmailer/CHANGELOG.md b/actionmailer/CHANGELOG.md
index 0ecb0235bc..b19d6b87c0 100644
--- a/actionmailer/CHANGELOG.md
+++ b/actionmailer/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Mails with multipart `format` blocks with implicit render now also check for
+    a template name in options hash instead of only using the action name.
+
+    *Marcus Ilgner*
+
 *   `config.force_ssl = true` will set
     `config.action_mailer.default_url_options = { protocol: 'https' }`