additional note about routes in functional tests for engines [ci skip]
Improve Contributing to Rails Guide

Logically group the content, so it makes more sense if someone tries to read from start of page to end of page. [ci skip]
Add documentation for Thread#freeze
Instead boat load of libraries, simply say StdLib
Use path where extensions are defined, not used

For consistency with all other documentation, point to where these core
extensions are defined, not where the example code comes from.

[ci skip]
Document LoadError core extensions

[ci skip]
Fix a few grammar issues. [ci skip]
Correct docs as singlton true is not returned here

[ci skip]
Fix spelling errors and grammar issues

Including replacing a few "smart quotes" with regular quotes (' and "),
for consistency.
[ci skip]
Remove wrapping div with inline styles for hidden form fields.

We are dropping HTML 4.01 and XHTML strict compliance since input
tags directly inside a form are valid HTML5, and the absense of
inline styles help in validating for Content Security Policy.
[ci skip] Use valid current config in example

`reaping_frequency` is used in Active Record `reap_frequency` is not
re-phrase how to run a test
Provide interface for accessing underlying IO object

In some cases users may need to work with/manipulate more of the
Tempfile api than provided by Upload. Allow users to get at the
underlying io via the common to_io method of IO/IO-like objects
[ci skip] PP does not generate pass by default

This was changed in https://github.com/rails/rails/pull/13415/files
[ci skip] document `statement_limit` 

Per discussion at https://github.com/rails/rails/issues/14645#issuecomment-40499409
SQL Like escaping helper method. [Rob Gilson & Yves Senn]

Closes #14222.

This is a follow up to #6104

This does not have the backwards compatibility issues brought up in
implementation to break.
Changed the NullRelation so that when count is called with #group it will properly return an empty hash instead of zero. Fixes issue #14721

Conflicts:
	activerecord/CHANGELOG.md
Merge pull request #11836 from mcfiredrill/engines-testing-doc

additional note about routes in functional tests for engines [ci skip]
`sanitize_sql_like` escapes `escape_character` not only backslash.

* This is a follow up to: fe4b0eee05f59831e1468ed50f55fbad0ce11e1d
* The originating PR is #14222
* It should fix the build
Merge pull request #14773 from eric-chahin/null_relation_fix

Changed the NullRelation so that when count is called with #group it wil...