https://gitlab.com/gitlab-org/gitlab-ce/builds/4710913

* upstream/master: (372 commits)
  Enable Lint/StringConversionInInterpolation cop and autocorrect offenses
  resolve duplicated changelog entry
  credit myself 😄
  change determine conditions
  override subject method in devise mailer
  follow the styleguide: Don't use parentheses around a literal
  wrap subject with method subject
  move spec back into shared example `an email sent from GitLab`
  stub config settings in spec
  remove empty line at block body end
  remove extra entry
  create new test in `spec/mailers/notify_spec.rb`
  move changelog to 8.13
  add configurable email subject suffix
  Fixes sidebar navigation.
  Convert "SSH Keys" Spinach features to RSpec
  Enable import/export back for non-admins
  Update gitlab-shell to 3.6.3
  Updated artwork of empty group state.
  Better empty state for Groups view.
  ...

Enable Lint/StringConversionInInterpolation cop and autocorrect offenses



See merge request !6654

Changed Slack service user referencing from full name to username

Closes #22737

See merge request !6624

Add configurable email subject suffix

## Why was this MR needed?

I noticed that there is a commit 44ab156e 3 years ago which removes email subject prefix

actually we do need an special part of the email subject which makes the email subject easy to identify

we just need to make it configurable rather than remove it.

See merge request !6172

Log sidekiq arguments as json

Logging the sidekiq job arguments as a ruby literal structure 
is akward. Specially when parsing the logs.

JSON is a standar format.



See merge request !3735

Resolve "Task List Checkbox Alignment"

## What does this MR do?

Replace the unmaintained `task_list` gem with the `deckar01-task_list` fork

## Are there points in the code the reviewer needs to double check?

 - I had to pin some dependencies in the fork to support `ruby < 2.2`, which added new version restrictions for 2 existing modules.
 - I triggered a build after I removed the patch to show the test passed with the new gem, then I removed the test, because this behavior is tested in the gem's repo now.

## Why was this MR needed?

 - The `task_list` patch was added with a comment that said it should be removed when merged upstream, but the repo got archived, so an upstream patch requires a fork.
 - #22470 can't be patched without warnings due to the way `task_list` uses Ruby constants.
 - There are additional outstanding `task_list` bugs that can be fixed once we switch to a fork.

## What are the relevant issue numbers?

 - #22466 
 - #22470
 - !6487

See merge request !6625

GrapeDSL for Award Emoji endpoints

Cherry-picked from !6330

See merge request !6629

Enable Import/Export for non-admin users

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21315

Related https://gitlab.com/gitlab-org/gitlab-ce/issues/20857 and https://gitlab.com/gitlab-org/gitlab-ce/issues/20821/

See merge request !6080

Use custom Ruby images to test builds

It allows us to remove redundant steps of installing required dependencies for every build.


See merge request !4506

Better empty state for Groups view.

Implemented @hazelyang's [awesome design](https://gitlab.com/gitlab-org/gitlab-ce/uploads/9141470ed121f137a4074ae4e12c449c/groups-empty.png) for empty group views.

Fixes #20829 


### Design
![https://gitlab.com/gitlab-org/gitlab-ce/uploads/9141470ed121f137a4074ae4e12c449c/groups-empty.png](https://gitlab.com/gitlab-org/gitlab-ce/uploads/9141470ed121f137a4074ae4e12c449c/groups-empty.png)


### Screenshots
![Screen_Shot_2016-09-28_at_13.43.35](/uploads/e2ab668a412596205deb67c97af78a1d/Screen_Shot_2016-09-28_at_13.43.35.png)

![Screen_Shot_2016-09-28_at_13.44.54](/uploads/c4301166f353f0ee198aecdc46cdfe66/Screen_Shot_2016-09-28_at_13.44.54.png)

![Screen_Shot_2016-09-28_at_13.46.10](/uploads/92024e866871969ec7a28db4b8e87220/Screen_Shot_2016-09-28_at_13.46.10.png)

![Screen_Shot_2016-09-28_at_13.46.20](/uploads/f1b515c7aa09d06e80a419d98ff76fd6/Screen_Shot_2016-09-28_at_13.46.20.png)

![Screen_Shot_2016-09-28_at_13.46.34](/uploads/76cdd5f0e9d3c59d017df26172f7dd4d/Screen_Shot_2016-09-28_at_13.46.34.png)

See merge request !6566

Convert "SSH Keys" Spinach features to RSpec

See merge request !6639

GrapeDSL for Keys endpoint

No changelog item as it doesn't change behaviour
Cherry-picket from !6330

See merge request !6631

Update GITLAB_SHELL_VERSION to 3.6.3

Because VERSION at the gitlab-shell v3.6.2 tag was still 3.6.1: https://gitlab.com/gitlab-org/gitlab-shell/blob/v3.6.2/VERSION (my bad!)

VERSION at the v3.6.3 tag is now 3.6.3: https://gitlab.com/gitlab-org/gitlab-shell/blob/v3.6.3/VERSION

See merge request !6621

Fix broken left sidebar navigation

Sidebar navigation is broken and it's introduced in !6627. Sidebar pin and hamburger icons were `a` tag before with `#` link on them. That was the main reason why page jumps to top. !6627 was trying to prevent default action but it interferes with the navigation links. I don't want to tweak event listeners for sidebar, instead I just replaced `a` elements with `div` because I think there is no point to have them as `a`.

/cc @dzaporozhets @jschatz1 

PS: This MR basically reverts !6627. I don't want to add another revert commit instead I reverted it in my editor and committed.

See merge request !6648

Add a /wip slash command to toggle the 'WIP' prefix in the MR title

## Why was this MR needed?

As explained in #21225, it prevents you from having to click through the entire edit form just to mark an MR as WIP.

Closes #21225

See merge request !6259