Do not try to write timestamps if they are missing #8813
remove unneeded test model for ActiveModel test cases.
Add link to minitest rdoc & github
[ci skip] Use appropriate mailer syntax.

Reference: https://github.com/rails/rails/commit/f7e4362011ceb1317fd401125d48d7ccb9a1079c
[ci skip] Remove duplicated last! section.

Reference: https://github.com/rails/rails/commit/d4fd0bd17709735ac91e434c94fe99429f078c6e

cc @schneems
Performed Returns true if redirect/render has happened
[ci skip] Normalize all localhost linking.
[ci skip] Mention the change in nil handling for serialized attributes
in "Upgrading from Rails 3.2 to Rails 4.0"
[ci skip] Clarify the "Serialized Attributes" section

Mention that the change in nil handling for serialized attributes
affects custom coders.
Remove @state.parent assignment on commit

This piece of code was introduced on
67d8bb963d5d51fc644d6b1ca20164efb4cee6d7 , which was calling
`committed?` in the `transaction_state` before calling the `committed!`
method. However on 7386ffc781fca07a0c656db49fdb54678caef809, the
`committed?` check was removed and replaced by a `finalized?`, which
only checks if the state is not nil. Thus we can remove that line.
Get request should not write to database note added. [skip ci]
Merge pull request #16329 from deependersingla/master

GET request should not write to database note added. [ci skip]
:nail_care: from #16329 [ci skip]
eval_block should be private
only ask for the routes module once

we can cache the module on the stack, then reuse it
pass the module to define_named_route_methods

after this, we can disconnect @module from the instance
helpers should be a Set so it doesn't grow unbounded

since helpers is a set, we can be confident about when to remove methods
from the module.
ask the named routes collection if the route is defined

we should not be accessing internals to figure out if a method is
defined.
oops! :bomb:

use helpers.include? so we don't get any false positives
Merge pull request #16335 from arthurnn/rm_parent_state_trasaction

Remove @state.parent assignment on commit