Fix habtm reflection
Conflicts:
    activerecord/CHANGELOG.md
    activerecord/lib/active_record/counter_cache.rb
    activerecord/lib/active_record/reflection.rb
    activerecord/test/cases/reflection_test.rb

fixed capitalization [ci skip]

avoid using alias in generators

[Guides] Add documentation for using Rails with a reverse proxy [ci skip]

Fixes URL generation with trailing_slash: true

Conflicts:
	actionpack/lib/action_dispatch/http/url.rb

This mirrors the layout of abstract adapter and puts the definitions
inside the `PostgreSQL` namespace (no longer under the adapter namespace).

/cc @kares

This reverts commit 7466d6a9, reversing
changes made to b850c4c5.

This was an accidental merge. A new PR will follow.

/cc @schneems

print generators on failed generate

[ci skip] Improve doc for ModuleConstMissing.guess_for_anonymous

Let's say we just ran:

```
$ rails g migrate add_click_to_issue_assignment
```

We will get an error that looks like: 

```
Could not find generator migrate.
```

This patch adds all existing migrations to the output to make it easier for a developer to find a valid migration. 

```
Could not find generator "migrate". Please select a valid generator:
Rails:
  assets
  controller
  generator
  helper
  integration_test
  mailer
  migration
  model
  resource
  scaffold
  scaffold_controller
  task
```


It would be nice to do some spelling detection and suggest alternatives, but for now this should  help.

Remove special case in schema dumper for decimal without scale

Fix router visualizer CSS and JS resources

I know, it's crazy.

Future port c8ddb617 [ci skip]

this also changes the constructor.  We don't need to pass more options
than "defaults" (whatever defaults are, ugh. probably another hash of
stupid stuff).

Remove duplicated parameter check on #where!

It seems that #where! is not designed to be used as a chained where.
See initial implementation at 8c2c6051.
So, no need to check twice.

We should not test #where!

https://github.com/rails/rails/pull/15285#discussion_r13018316

update select_tag docs for customizing id

Simplify the code in schema cache

Bring the missing parameters back.

Remove `Column#primary`

It appears to have been used at some point in the past, but is no longer
used in any meaningful way. Whether a column is considered primary is
a property of the model, not the schema/column. This also removes the
need for yet another layer of caching of the model's schema, and we can
leave that to the schema cache.

Array#to now accept negative position also.

Added force_reload to Auto-generated methods doc

Move parsing of PG sql strings for defaults out of column

add test cases for negative position in Array#from

Remove duplicated setup in test