add include_hidden option to collection_check_boxes helper
Save has_one associations only if record has changes

Prevents save related callbacks such as `after_commit` being
triggered when `has_one` objects are already persisted and have no
changes.
Don't load test env by default
Only use BINARY for mysql case sensitive uniqueness check when column has a case insensitive collation.
Add tip about using RDoc's --pipe command to quickly test the output of
a piece of documentation.

This can be useful for trying out combinations of markup and code, as
discussed in rails/rails@225bcad
Introduce `render :body` for render raw content

This is an option for sending a raw content back to browser. Note that
this rendering option will unset the default content type and does not
include "Content-Type" header back in the response.

You should only use this option if you are expecting the "Content-Type"
header to not be set. More information on "Content-Type" header can be
found on RFC 2616, section 7.2.1.

Please see #12374 for more detail.
Update hash format for render_text_test
Introduce `render :plain` for render plain text

This is as an option to render content with a content type of
`text/plain`. This is the preferred option if you are planning to render
a plain text content.

Please see #12374 for more detail.
Introduce `render :html` for render HTML string

This is an option for to HTML content with a content type of
`text/html`. This rendering option calls `ERB::Util.html_escape`
internally to escape unsafe HTML string, so you will have to mark your
string as html safe if you have any HTML tag in it.

Please see #12374 for more detail.
Fix a fragile test on `action_view/render`

This test were assuming that the list of render options will always be
the same. Fixing that so this doesn't break when we add/remove render
option in the future.
Cleanup `ActionController::Rendering`
Update guides for new rendering options

* Introduces `:plain`, `:html`, `:body` render option.
* Update guide to use `render :plain` instead of `render :text`.
Add missing CHANGELOG entry to Action View
Add `#no_content_type` attribute to `AD::Response`

Setting this attribute to `true` will remove the content type header
from the request. This is use in `render :body` feature.
Update upgrading guide regarding `render :text`
Merge pull request #14062 from sikachu/ps-render-format

Introduce `:plain`, `:html`, and `:body` render options.
Sync 4.1 release notes with changes since 7f648bc7 [ci skip]
Merge pull request #14097 from chancancode/sync_4_1_release_notes

Sync 4.1 release notes with changes since 7f648bc7
Escape format, negative_format and units options of number helpers

Previously the values of these options were trusted leading to
potential XSS vulnerabilities.

Fixes: CVE-2014-0081
Correctly escape PostgreSQL arrays.

Thanks Godfrey Chan for reporting this!

Fixes: CVE-2014-0080