Rather than just changing it and hoping for the best.

Requested by @jeremy:

https://github.com/rails/rails/commit/ba1544d71628abff2777c9c514142d7e9a159111#commitcomment-2106059

Removing duplication in callback normalization.

These two things were 100% identical.

:counter_cache option for  to support custom named counter caches

So that the scope may be a NullRelation and return a result without
executing a query.

Fixes #7928

Fixes #8102.

I couldn't find a nicer way to deal with this than delegate the call to
 #scope, which will be a NullRelation when we want it to be.

This allows us to avoid hacks like the "return 0 if owner.new_record?"
in #count (which this commit removes).

Also, the relevant foreign key may actually be present even on a new
owner record, in which case we *don't* want a null relation. This logic
is encapsulated in the #null_scope? method.

We also need to make sure that the CollectionProxy is not 'infected'
with the NullRelation module, or else the methods from there will
override the definitions in CollectionProxy, leading to incorrect
results. Hence the nullify: false option to CollectionAssociation#scope.
(This feels a bit nasty but I can't think of a better way.)

delegate PathSet's enumerator methods

Fix message about include_blank option. [ci skip]

For example, the following should not run any query on the database:

Post.new.comments.where(body: 'omg').to_a # => []

Fixes #5215.

Add note about squashing in contributor guide.

We tell people how to do this all the time in the Issues tracker,
so now we can just point them here.

See
https://github.com/rails/rails/commit/cb7d19b66badfbd1846c195913419c331701074e#commitcomment-2127148.

not raise so many exceptions:

  https://github.com/rails/rails/blob/master/actionpack/lib/action_view/template.rb#L126

irb(main):001:0> class Foo; def method_missing(*args); super; end end
=> nil
irb(main):002:0> $DEBUG = true
=> true
irb(main):003:0> Array(Foo.new)
Exception `NoMethodError' at (irb):1 - undefined method `to_ary' for #<Foo:0x007f854390e488>
Exception `NoMethodError' at (irb):1 - undefined method `to_a' for #<Foo:0x007f854390e488>
=> [#<Foo:0x007f854390e488>]
irb(main):004:0>

Kernel#capture replaced by version which can catch output from subprocesses

Reformat gemspec

This reverts commit 36376560, reversing
changes made to 3148ed9a.

Conflicts:
	actionpack/lib/action_dispatch/middleware/flash.rb

Reason: it broke Sam's CI

https://github.com/rails/rails/pull/8017#issuecomment-10210655

Organized the gemspec files a bit.

 * Made quotes more consistent (single quotes dominated, so I used
   that).
 * Moved license line down a line, separating it logically, and removed
   the extra whitespace before its = operator.
 * Minor whitespace fixes.

Store FlashHashes in the session as plain hashes

handle trailing slash with engines (test case for #7842)

Add test to avoid regression of 58e48d52

[ci skip]

Add app Rake tasks when -T and --dummy-path is passed to `plugin new`

Closes #8121

The `plugin new` generator always adds the dummy app rake tasks,
when a dummy app was created.

This is already handled by #find, it's a duplicate check, since
find_with_ids is not called from anywhere else.

Commit 65a2977c has introduced some
changes to format content for small devices, this change reverts the
original font size for normal screens while maintaing the same format
for these devices.

[ci skip]

[ci skip]