Store FlashHashes in the session as plain hashes rather than custom objects with unstable class names and instance variables.

Refactor FlashHash to take values for its ivars in the constructor, to pretty up FlashHash.from_session_value.

Remove stale comment on FlashHash: it is no longer Marshaled in the session so we can change its implementation.

Remove blank lines I introduced in controller/test_case.rb.

Unit tests for FlashHash#to_session_value.

Put in a compatibility layer to accept FlashHash serializations from Rails 3.0+.

Test that Rails 3.2 session flashes are correctly converted to the new format.

Remove code path for processing Rails 3.0 FlashHashes since they can no longer deserialize.

Fix session['flash'] deletion condition: it will never be empty?, it will either be nil or a hash with 'discard' and 'flashes' keys.
Delegate all calculations to the scope.

So that the scope may be a NullRelation and return a result without
executing a query.

Fixes #7928
Merge pull request #8116 from senny/7993_configure_counter_cache_for_has_many

:counter_cache option for  to support custom named counter caches
Removing duplication in callback normalization.

These two things were 100% identical.
Merge pull request #8157 from steveklabnik/remove_callback_duplication

Removing duplication in callback normalization.
Fix default cache store documentation.

It's actually the FileStore.

Fixes #8130.
Add note about asset pipeline and CDNs.

Fixes #2468.
Further explain the CDN and caching situation.
Properly deprecate ConnectionHandler#connection_pools

Rather than just changing it and hoping for the best.

Requested by @jeremy:

https://github.com/rails/rails/commit/ba1544d71628abff2777c9c514142d7e9a159111#commitcomment-2106059
fix warnings
Remove not used load hooks for active_record_config

These were removed with ActiveRecord::Model in
https://github.com/rails/rails/commit/9e4c41c903e8e58721f2c41776a8c60ddba7a0a9#L15L156
Deprecate Hash#diff.

It's no longer used in Rails any more.

See https://github.com/rails/rails/pull/8142\#issuecomment-10227297 for more
Merge pull request #8158 from steveklabnik/deprecate_diff

Deprecate Hash#diff.
change rdoc syntax for adecuate render [ci-skip]
correct link syntax [ci-skip]
Gracefully handle upgrading apps with mass assigment configs

Most apps upgrading from 3.x will have options for mass assigment in
their application.rb and environments/*.rb config files. Rather than
just raising a NoMethodError when copying the config, this commit
adds a warning message until either the protected_attributes gem
is installed or the relevant config options are removed.
update syntax and add note about prompt use of HttpHelpers [ci-skip]
Use get in the redirection doc examples

get is the most common usage, and match without an explicit verb
was disallowed in 56cdc81c08b1847c5c1f699810a8c3b9ac3715a6.

[ci skip]
Trivial documentation fix for ActiveModel::Naming comment.
Merge pull request #8162 from fimmtiu/master

Trivial documentation fix for ActiveModel::Naming comment [ci skip]