Fix has_many though associations when the through association is singular

[pi-plus-45x23]

Attempting to reify a has_many through: association throws an error when the through: association is not has_many.

Suppose we have these associations defined:

class Post < ActiveRecord::Base
  has_one :content
  has_many :content_blocks, through: :content
end

Executing

post.versions.last.reify(has_many: true)

raises NoMethodError here if post.content is nil and here otherwise.

Wrapping the through association in an Array will fix the error. However, the given example will still produce incorrect results because we aren't reifying the content association with has_one: true. Thus, the HMT association should implicitly reify the through association regardless of the options given to reify.

[westonganger]

Merged. Thanks for your contribution!