Create 4.2 release notes guide scaffold [ci skip]

Point to future 4-2-stable branch for detailed changes. [ci skip]

Sync Active Support changelogs with release notes [ci skip]

4.2 Release Notes is a work in progress [ci skip]

Assorted fixes for AS release notes [ci skip]

* `Hash#deep_transform_keys` has already been backported
* Mentioning `ActiveSupport::SafeBuffer#prepend` in the "Deprecations" section would be enough
* Fix syntax in `Kernel#concern` example

Sync AS release notes with the latest commits [ci skip]

Synced 4.2 release notes with commits in railties [ci skip]

Sync AP Deprecations and Notable changes from CHANGELOG [ci skip]

Removed 4.2 release notes from the index [ci skip]

This deprecation was reverted in 489a8f2 [ci skip]

Synced Active Record changelogs for 4.2 release notes [ci skip]

Synced Active Model changelog with the release notes [ci skip]

Added cc26b6b as a 'Removal' item in AP release notes [ci skip]

Use 'character' instead of 'symbol' to avoid confusion [ci skip]

Edit pass on 4.2 release notes [ci skip]

:memo: :lipstick: Use `.xyz` and `#xyz` appropiately [ci skip]

1 files changed, 6 insertions, 0 deletions

diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 03d1f2a3a0..6800e71a3c 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -22,6 +22,12 @@ Rails generally stays close to the latest released Ruby version when it's releas
 
 TIP: Ruby 1.8.7 p248 and p249 have marshaling bugs that crash Rails. Ruby Enterprise Edition has these fixed since the release of 1.8.7-2010.02. On the 1.9 front, Ruby 1.9.1 is not usable because it outright segfaults, so if you want to use 1.9.x, jump straight to 1.9.3 for smooth sailing.
 
+Upgrading from Rails 4.1 to Rails 4.2
+-------------------------------------
+
+NOTE: This section is a work in progress.
+
+
 Upgrading from Rails 4.0 to Rails 4.1
 -------------------------------------