This reverts commit fa6d921e.

Reason: Not a fan of such massive changes. We usually close such changes
if made to Rails master as a pull request. Following the same principle
here and reverting.

[ci skip]

For future reference, this is the regex I used: ^\s*#\s*\n(?!\s*#). Replace
with the first match, and voilà! Note that the regex matches a little bit too
much, so you probably want to `git add -i .` and go through every single diff
to check if it actually should be changed.

Record.from("(#{sub_query.to_sql})")    -> Record.from(sub_query)
Record.from("(#{sub_query.to_sql}) a")  -> Record.from(sub_query, :a)

This helps bring the interfaces of CollectionProxy and Relation closer
together, and reduces the delegation backflips we need to perform.

For example, first_or_create is defined thus:

class ActiveRecord::Relation
  def first_or_create(...)
    first || create(...)
  end
end

If CollectionProxy < Relation, then post.comments.first_or_create will
hit the association's #create method which will actually add the new record
to the association, just as post.comments.create would.

With the previous delegation, post.comments.first_or_create expands to
post.comments.scoped.first_or_create, where post.comments.scoped has no
knowledge of the association.

The main reason for this is that I want to separate the code that does
the mutating from the code that does the cloning.

add test to show offset query_methods on mysql & mysql2

change test to cover public API

And added NullRelation class implementing the null object pattern for the `Relation` class.

Also, fixed the bit about returning AM::MissingAttributeError. This
seems to be fixed earlier in 3-2-stable only.

This reverts commit 0df27c98.

Reverted due to failing test, see #2845.

Replace split on comma with a regexp that will reverse all ASC/DESC specifically

The join_nodes must be passed to the JoinDependency initializer and therefore counted by the alias tracker. This is because the association_joins are aliased on initialization and then the tables are cached, so it is no use to alias the join_nodes later. Fixes #2556.

This reverts commit 9d396ee8, reversing
changes made to fa2bfd83.

Reason: the change broke the build.

This reverts commit 04cc446d.

I reverted it because apparently we want to use: select([:a, :b])
instead of select(:a, :b), but there was no tests for that form.

This reverts commit 9d396ee8, reversing
changes made to fa2bfd83.

Reason: the change broke the build.

This reverts commit 04cc446d.

I reverted it because apparently we want to use: select([:a, :b])
instead of select(:a, :b), but there was no tests for that form.

having raises NoMethodError: undefined method `empty?' when a Fixnum or Date/Time were passed via varargs