Revert "incorrect content of models/comment.rb after 'rails generate'"

This reverts commit 0f0803fda5df60319d8646bb4f3e71f2e596316a.

Reason: The content was correct since attr_accessible was removed from
rails master.
Don't call after_commit when creating through an association and save fails, fixes #5802
Merge pull request #9115 from bensie/issue_5802

Don't call after_commit when creating through an association and save fails, fixes #5802
9253: Before writing a numeric attribute value, ActiveRecord does an implicit
conversion of boolean types (true => 1 and false => 0). If the numeric value
being assigned is a BigDecimal, then ActiveRecord compares a BigDecimal to
true and false. This is known to be very slow in Ruby 1.9.3.
Merge pull request #9254 from warnickr/9253_avoid_bigdecimal_performance_issue

Before writing a numeric attribute value, ActiveRecord does an implicit conversion of boolean types (true => 1 and false => 0). If the numeric value being assigned is a BigDecimal, then ActiveRecord compares a BigDecimal to true and false.

This is known to be very slow in Ruby 1.9.3 (see http://www.ruby-forum.com/topic/4409452 and https://bugs.ruby-lang.org/issues/7645#change-35188).

The Ruby core team has implemented a fix for this issue that will be included in Ruby 2, but they appear to have no intention of back-porting this fix to Ruby 1.9.3. In my case, the performance impact of this issue was enormous (200% - 300% performance hit) for some of the pages in my application.

See c75b5a88a82c79fdf95dfea4d72bf3c5a829930e applied to 3-2-stable branch for more reasoning and a benchmark.
Make valid_type? public
Merge pull request #9283 from rubys/master

Make valid_type? public
Bump rack-test dependency to 0.6.2
Merge pull request #9285 from rahul100885/master

Bump rack-test dependency to 0.6.2
don't cache invalid subsets when preloading hmt associations.

closes #8423.
Merge pull request #9252 from senny/8423_hmt_preloading_bug

don't cache invalid subsets when preloading hmt associations
Merge pull request #8704 from senny/remove_regexp_global_from_url_for

replace regexp global in #url_for
Added extra comment when a migration already exists of the same name.
User should know that he can overwrite the previous migration. This
comes in handy especially when generating models which were previously
created then removed.
Merge pull request #9298 from wangjohn/add_documentation_to_migration_collision

Added extra comment when a migration already exists of the same name
Revert "Merge pull request #9206 from ranjaykrishna/use_define_method"

This reverts commit 1fc6876b57f2e1d31731e74eb4271b5655e746d2, reversing
changes made to 0268b5d8cdc3c5a1337462135f0a326a2654ba1a.

Reason: failing test

  1) Error:
test_valid_column(ActiveRecord::ConnectionAdapters::SQLite3AdapterTest):
NoMethodError: undefined method `column' for
    test/cases/adapters/sqlite3/sqlite3_adapter_test.rb:29:in
`test_valid_column'
Revert "Revert "Merge pull request #9206 from ranjaykrishna/use_define_method""

This reverts commit 8aa4603a5adaa56c818a7bd1c0b761b4ecca3d3e.

Reverting the revert because I reverted the wrong thing! Fail.
Revert "checking in the abstractions for valid type checking:"

This reverts commit c321b309a9a90bbfa0912832c11b3fef52e71840.

Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
	activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

Reason: failing test

  1) Error:
test_valid_column(ActiveRecord::ConnectionAdapters::SQLite3AdapterTest):
NoMethodError: undefined method `column' for
    test/cases/adapters/sqlite3/sqlite3_adapter_test.rb:29:in
`test_valid_column'
Revert "Make valid_type? public"

This reverts commit 5d528f835e871f5f9d4b68e8a81cfbe900b7e718.

Relates to f8c8ad5 which is also getting reverted due to failing test.
copy edits [ci skip]
Merge branch 'master' of github.com:lifo/docrails

Conflicts:
	guides/source/upgrading_ruby_on_rails.md