TS::Cache#compute_if_absent guarantees that only a single thread will get to execute the provided block for a given key.

Migrations Guide: Fix line length [ci skip]

side of a hm:t association along with preloading.

Fixed grammatical typo in configuring.md guide.

Getting Started Guide: Fix code container in Chapter 5.2 [ci-skip]

Getting Started Guide: Update sentence in Chapter 5.8 [ci-skip]

Remove HelperyTestHelper not used in any test

Add new line after create action on CommentsController code example [ci skip]

Adds template dependencies rake task from cache_digests gem.

This adds the rake tasks `cache_digests:dependencies` and `cache_digests:nested_dependencies` from `cache_digests` gem.

[ci skip] Update scaffold output and change some words.

Scaffold output: add jbuilder, update timestamp (edge guide!)

Add some file breadcrumb (comment) to help reader find files.

Improve readability by adding some command outputs.

Thanks for great help from @senny.

Getting Started Guide: post.rb -> Post [ci skip]

[ci skip] escape unintended url in docs

added "id: false" to HABTM join table example [ci skip]

Getting Started Guide: posts_controller -> PostsController [ci skip]

[ci skip] Add missing periods in active_record_basics.md.

Correct error in ActiveRecord Querying guide [ci skip]

Getting Started Guide: update link_to string argument to use single-quote [ci skip]

Getting Started Guide: update link_to string argument to use single-quote mark, following document style [ci skip]

Fix small typo in docs

fix .find when inverse is loaded

.find([1]) should return an Array of entries, even when a invese object is in memory already

Make sure inverse_of is visible on the has_many callbacks

* master: (62 commits)
  Getting Started Guide: Hello Rails! -> Hello, Rails! and wrap code tag
  Add CHANGELOG entry for #12344
  Add regression test to #12343
  Fix typo in number_to_human docs: you -> your
  [Documentation] Add a missing validation to I18n docs
  Use the given name in html_options for the hidden field in collection_check_boxes
  assign_attributes should return if argument is blank.
  No need the else clause
  Use join to concat the both side of the AST
  Add a CHANGELOG entry about Web Console inclusion
  added column type to example in section 2.3
  Include web-console in new projects Gemfile
  ActiveRecord::ConnectionAdapters::Column.string_to_time method respects string with timezone. Closes #12278.
  add test_scoped_root_as_name
  Getting Started Guide: update RubyGems Guides link [ci skip]
  Deprecate unused quoted_locking_column method.
  Update references to wycats/thor to erikhuda/thor.
  bcrypt-ruby v3.1.2 supports Ruby 2.0 on Windows
  Fix the model name in the association basics guides
  We shouldn't override PostgreSQLAdapter's superclass inheritance while monkeypatching
  ...