[ci skip] Prefer credentials to secrets in docs.

Removes most mentions of secrets.secret_key_base and explains
credentials instead.

Also removes some very stale upgrade notices about Rails 3/4.

2 files changed, 3 insertions, 3 deletions

diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index 6ce8b0b2d9..abfec90b6d 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -403,12 +403,12 @@ module Rails
     end
 
     # The secret_key_base is used as the input secret to the application's key generator, which in turn
-    # is used to create all the MessageVerfiers, including the one that signs and encrypts cookies.
+    # is used to create all MessageVerifiers/MessageEncryptors, including the ones that sign and encrypt cookies.
     #
     # In test and development, this is simply derived as a MD5 hash of the application's name.
     #
     # In all other environments, we look for it first in ENV["SECRET_KEY_BASE"],
-    # then credentials[:secret_key_base], and finally secrets.secret_key_base. For most applications,
+    # then credentials.secret_key_base, and finally secrets.secret_key_base. For most applications,
     # the correct place to store it is in the encrypted credentials file.
     def secret_key_base
       if Rails.env.test? || Rails.env.development?
diff --git a/railties/lib/rails/commands/credentials/USAGE b/railties/lib/rails/commands/credentials/USAGE
index 5bd9f940fd..85877c71b7 100644
--- a/railties/lib/rails/commands/credentials/USAGE
+++ b/railties/lib/rails/commands/credentials/USAGE
@@ -10,7 +10,7 @@ to get everything working as the keys are shipped with the code.
 === Setup
 
 Applications after Rails 5.2 automatically have a basic credentials file generated
-that just contains the secret_key_base used by the MessageVerifiers, like the one
+that just contains the secret_key_base used by MessageVerifiers/MessageEncryptors, like the ones
 signing and encrypting cookies.
 
 For applications created prior to Rails 5.2, we'll automatically generate a new