Merge pull request #12479 from benpickles/unshift-middleware

Expose MiddlewareStack#unshift to environment configuration
Merge pull request #12283 from JuanitoFatas/rails-on-rack

[ci skip] Add explanation on Rack::Sendfile middleware in rails_on_rack.md.
observers are not part of ActiveModel [ci skip]
Typo fix [ci skip]

Fixing the typo which is formed a not required link.  Check
here http://api.rubyonrails.org/classes/ActionController/Base.html
under paramters section
keeping it under tt tag

gets reverted here ec8ef1e1055c4e1598da13f49d30261f07f4a9b4
Using flat_map instead of map and flatten

original commit 8998441967a8cfc6e4302c29664ab9d0acd77704

Reverted here ec8ef1e1055c4e1598da13f49d30261f07f4a9b4
Minor align BR tags with HTML void - with reference to the generators code change - https://github.com/rails/rails/commit/f038d4cc5fe1ac21f92c7e32c61ff85a0c816f3f
Added ActionView in rake about [ci skip]
Merge pull request #12481 from arunagw/fixes

Few fixes which includes revert fixes
[Validations Guide] Add full stop to the end of sentence [ci skip]
Merge pull request #12482 from francisgo/patch-11

[Validations Guide] Add full stop to the end of sentence [ci skip]
FakeController is not required in AV
Moved viewpathstest into actionview/test/actionpack/controller


These test were not running at all,
Now it will run as a tests part.
Merge pull request #12485 from arunagw/code-removal

viewpathtests file moved
convert JoinBase to a tree and remove the Node class
push parent up to the superclass

We always want a linked list back to the root node.
Modifies the initialization guide to make the initializers process clearer and remove a TODO. [ci skip]
remove == so we can see where walking up parents occurs
make node search more efficient

Rather than search every node in the tree, comparing that node and all
of its parents every time, start at the root from both sides and work
our way down the tree
speed up finding existing nodes

The node must be a child of the parent passed in, so only search
children of the parent node
just skip the join if it's already there

Remove the annoying `find_or_build` stuff.