[Rails5] Update Event#subclass_from_attributes method

See merge request gitlab-org/gitlab-ce!18312

Link Monitor docs to the front page

Closes #45006

See merge request gitlab-org/gitlab-ce!18314

Resolve "tree/master shows incorrect CI build status"

Closes #44541

See merge request gitlab-org/gitlab-ce!17995

Replace vue resource with axios for pipeline details page

See merge request gitlab-org/gitlab-ce!18285

Client implementation for InfoAttributes

See merge request gitlab-org/gitlab-ce!18261

Resolve "Illustration for the case where the job has finished and the log was erased"

Closes #45159

See merge request gitlab-org/gitlab-ce!18253

Clients can now request the attributes from `$GIT_DIR/info/attributes`
through Gitaly. The Gitaly migration is described in gitlab-org/gitaly#1082.

The parser algorithm was implemented in a way it could handle both file
contents or a File handle, and both were already tested.

Other than that, using the boy scout rule, I've removed a class,
InfoAttributes, as it was delegating everything to the parser and
therefor wasn't really needed in my opinion.

Resolve "Clean outdated flaky specs from the flaky specs report"

Closes #37721

See merge request gitlab-org/gitlab-ce!18196

Replace the `project/issues/milestones.feature` spinach test with an rspec analog

See merge request gitlab-org/gitlab-ce!18300

Replace the `project/commits/branches.feature` spinach test with an rspec analog

See merge request gitlab-org/gitlab-ce!18302

Resolve "When editing a comment in an issue, the preview mode is toggled in the main textarea"

Closes #44697

See merge request gitlab-org/gitlab-ce!18303

In Rails 5.0 the `ActiveRecord::Inheritance::subclass_from_attributes`
method was updated.
Now it calls the `find_sti_class` method [1] which is overriden in the `Event`
model and returns needed class (`Event` vs `PushEvent`).

[1]: https://github.com/rails/rails/blob/5-0-stable/activerecord/lib/active_record/inheritance.rb#L209

This commit fixes the errors like
```
143) User#contributed_projects doesn't include IDs for unrelated projects
      Failure/Error: action = attrs.with_indifferent_access[inheritance_column].to_i

      NoMethodError:
        undefined method `with_indifferent_access' for nil:NilClass
      # ./app/models/event.rb:118:in `subclass_from_attributes'
```
which are raised on the `RAILS5=1 rspec ...` command.

Branch with a commit detection defaults to Gitaly

See merge request gitlab-org/gitlab-ce!18304

Tag with a commit detection defaults to Gitaly

See merge request gitlab-org/gitlab-ce!18305

Fix file-specific variables collection item option

Closes gitlab-ee#5444

See merge request gitlab-org/gitlab-ce!18307

Fixed markdown preview in IDE not working for new files

See merge request gitlab-org/gitlab-ce!18287

[Rails5] Fix admin/application_settings_controller

See merge request gitlab-org/gitlab-ce!18275

By default this was an OPT_IN RPC, and now graduates to OPT_OUT as the
acceptance testing was successful in:
gitaly#1009

This follows the conventions of our [migration
process](https://gitlab.com/gitlab-org/gitaly/blob/master/doc/MIGRATION_PROCESS.md)

By default this was an OPT_IN RPC, and now graduates to OPT_OUT as the
acceptance testing was successful in:
https://gitlab.com/gitlab-org/gitaly/issues/1008

This follows the conventions of our [migration
process](https://gitlab.com/gitlab-org/gitaly/blob/master/doc/MIGRATION_PROCESS.md)

[CE Backport] Fix email handler spec for EE

See merge request gitlab-org/gitlab-ce!18298

The `RAILS5=1 rspec spec/controllers/admin/application_settings_controller_spec.rb`
command throws the error:

Failures:

  1) Admin::ApplicationSettingsController PUT #update falls back to defaults when settings are omitted
      Failure/Error: import_sources = params[:application_setting][:import_sources]

      NoMethodError:
        undefined method `[]' for nil:NilClass
      # ./app/controllers/admin/application_settings_controller.rb:62:in `application_setting_params'

This commit fixes it.

Fix enviroments seeding on certain branch names

Closes #45051

See merge request gitlab-org/gitlab-ce!18263

Update vendored .gitlab-ci.yml for Auto-Devops

See merge request gitlab-org/gitlab-ce!18289

Use axios in the stage component

See merge request gitlab-org/gitlab-ce!18286

Make sure hooks run when seeding admin user

Closes gitlab-development-kit#335

See merge request gitlab-org/gitlab-ce!18284

[Rails5] Fix running spinach tests

See merge request gitlab-org/gitlab-ce!18281

Reduce complexity of issuable finder query.

Closes #37125

See merge request gitlab-org/gitlab-ce!18219