Verify that route constraints respond to the expected messages instead of silently failing to enforce the constraint
Refactor AR's validations_test.rb

The `:context` switch feature is implemented in
ActiveRecord::Validations#valid? method, so we should rename the test
names, and execute `valid?` in the test.

Change test name in AR's validations_test.rb

This test is testing save method's code
Fix bugs with changed attributes tracking when transaction gets rollback
Fix Hash#deep_merge bug and improve documentation — resolves #12738

Previously merging into a hash with a falsy value would not result in
the merge-block being called. The fix is simply to check for presence
of the key in the hash.

The documentation example for `deep_merge` now appropriately
demonstrates what a deep merge does.
Fixed custom validation context bug where child
associations were not being saved.

Fixes #13854.

[Eric Chahin, Aaron Nelson, & Kevin Casey]
always pass options to the _url method
only add the optiosn if they are not empty

I think this is wrong, but it gets the build passing for now. We should
always add options, but we need to make more guarantees about how the
underlying url helper is called
Form_tag_helper grammar fix [skip ci]
Merge pull request #14939 from jonatack/patch-8

Form_tag_helper grammar fix [skip ci]
Enhance a bit a few changelog entries [ci skip]
Follow up to 38ad5438 [ci skip]

This commit adds new lines between titles, paragraphs and code blocks
for an easier reading.

Moreover, in order to be consistent with the other guides, let's remove
the sharps on the right side of the different titles.

The "Running a Single Test" part was also explained after the "Testing
Active Record" one which shows how to run a single test under the scope
of a specific adapter.

Finally, let's explain the `-n` option to run a specific test method.
[ci skip] Update guides license to CC BY-SA 4.0 International.

Benefits: https://creativecommons.org/version4
Added link for 4.1 guides on edge guide [ci skip]
Tiny follow up to #14915 [ci skip]
Automaticly add username and email if configured in git-scm, as bundle gem
Works correctly if git not installed
skip-git should not hit git commands plugin generators
Merge pull request #14941 from arunagw/hbakhtiyor-new-plugin-command-advanced-config

Plugin gemspec
Merge pull request #14942 from JuanitoFatas/patch/cc-by-sa-4-0

[ci skip] Update guides license to CC BY-SA 4.0 International.
Add singular and plural form for some validation messages