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.
Fixed typo [ci skip]

singular is more suited to
change to "check out"
e-mail => email, and subject/verb agreement
add punctuation
Remove duplicate configuration option for ActiveSupport [ci skip]

Fixes rails/rails#13732
`requies` => `requires`
`easiy` => `easy`
`framwork` => `framework`
Remove old comments about suppressing warnings.
Upgraded jquery-rails gem version
Fixed spelling error: `extracetd` => `extracted`
docs, Cookie values are String based. Closes #12860. [ci skip]
Rely on backticks instead of tt tags [ci skip]

Since the language in code blocks is inferred, if the code contains tt
tags, the block will be parsed as XML for instance while it is Ruby.
context in validation goes through has many relationship
Updated the cookie docs to use the safer JSON.{generate,parse}

cc @senny
Add test case for autosave HasMany with accepts_nested_attributes.

It should not save the parent record when the nested attributes are
invalid.

Test case to cover #8194.