Added test to ensure that DescendantsTracker does not leak memory on singleton classes
Change ActionController::Parameters#require behavior when value is empty
When the value for the required key is empty an ActionController::ParameterMissing is raised which gets caught by ActionController::Base and turned into a 400 Bad Request reply with a message in the body saying the key is missing, which is misleading.

With these changes, ActionController::EmptyParameter will be raised which ActionController::Base will catch and turn into a 400 Bad Request reply with a message in the body saying the key value is empty.
Exception handling for controllers using ActionController::Live

Any exceptions that occured at the view or controller level for a
controller using ActionController::Live would cause the server to either
hang with an open socket indefinitely, or immediately crash (depending
on whether the server was launched with rails s or directly). Changed
the behavior of exceptions to act the same as streaming templates for
html requests, and allow for an on_error callback if needed.
rails commands even if bin/rails is a gem stub
failure to parse params should trigger a 400 Bad Request
Remove “Sweepers” from Caching TOC and mention Page/Action caching are removed
script/rails could never be from bundler
need to delete bin, not binstub, update wording
Improve poor security recommendation in docs

As reported in #9960, the current documentation recommends an insecure practice for
key generation from a password (a single round of SHA-256). The modified documentation
uses ActiveSupport::KeyGenerator to perform proper key stretching.
Revert "Using American English spellings over British style spellings"

This reverts commit 573df1cf2a5d5d1f288c8a4a5d76194675141832.

Reason: changelog edits aren't allowed in docrails.

[ci skip]
Merge branch 'master' of github.com:rails/rails
minor copy editing
fix binstub typo
Fix typo
Remove unnecessary / confusing code in example
as of Rails 3.2.13 it appears that importing an engine's migration into the host app is achieved by rake blorgh_engine:install:migrations
fixed a article link at sitepoint
Merge pull request #132 from hlee/master

Fixed an article link at sitepoint
Merge pull request #129 from rafBM/master

Remove “Sweepers” from Caching TOC and mention Page/Action caching removal
Proofreading tweaks to the Mailer guide