Update housekeeping docs for new GitLab UI.

I spent far too much time trying to find this button.

See merge request !6679

Fix project deletion when feature visibility is set to private

Projects that are destroyed are put in the pending_delete state.
The ProjectDestroyWorker checks whether the current user has
access, but since the ProjectFeature class uses the default scope
of the Project, it will not be able to find the right project.

This was a regression in 8.12 that caused the following stack trace:

```
NoMethodError: undefined method `team' for nil:NilClass
  from app/models/project_feature.rb:62:in `get_permission'
  from app/models/project_feature.rb:34:in `feature_available?'
  from app/models/project.rb:21:in `feature_available?'
  from app/policies/project_policy.rb:170:in `disabled_features!'
  from app/policies/project_policy.rb:29:in `rules'
  from app/policies/base_policy.rb:82:in `block in abilities'
  from app/policies/base_policy.rb:113:in `collect_rules'
  from app/policies/base_policy.rb:82:in `abilities'
  from app/policies/base_policy.rb:50:in `abilities'
  from app/models/ability.rb:64:in `uncached_allowed'
  from app/models/ability.rb:58:in `allowed'
  from app/models/ability.rb:49:in `allowed?'
  from app/services/base_service.rb:11:in `can?'
  from lib/gitlab/metrics/instrumentation.rb:155:in `block in can?'
  from lib/gitlab/metrics/method_call.rb:23:in `measure'
  from lib/gitlab/metrics/instrumentation.rb:155:in `can?'
  from app/services/projects/destroy_service.rb:18:in `execute'
```

Closes #22948

See merge request !6688

Projects that are destroyed are put in the pending_delete state.
The ProjectDestroyWorker checks whether the current user has
access, but since the ProjectFeature class uses the default scope
of the Project, it will not be able to find the right project.

This was a regression in 8.12 that caused the following stack trace:

```
NoMethodError: undefined method `team' for nil:NilClass
  from app/models/project_feature.rb:62:in `get_permission'
  from app/models/project_feature.rb:34:in `feature_available?'
  from app/models/project.rb:21:in `feature_available?'
  from app/policies/project_policy.rb:170:in `disabled_features!'
  from app/policies/project_policy.rb:29:in `rules'
  from app/policies/base_policy.rb:82:in `block in abilities'
  from app/policies/base_policy.rb:113:in `collect_rules'
  from app/policies/base_policy.rb:82:in `abilities'
  from app/policies/base_policy.rb:50:in `abilities'
  from app/models/ability.rb:64:in `uncached_allowed'
  from app/models/ability.rb:58:in `allowed'
  from app/models/ability.rb:49:in `allowed?'
  from app/services/base_service.rb:11:in `can?'
  from lib/gitlab/metrics/instrumentation.rb:155:in `block in can?'
  from lib/gitlab/metrics/method_call.rb:23:in `measure'
  from lib/gitlab/metrics/instrumentation.rb:155:in `can?'
  from app/services/projects/destroy_service.rb:18:in `execute'
```

Closes #22948

Fix todos page mobile viewport layout

## What does this MR do?
Fixes the todos page mobile viewport layout

## Are there points in the code the reviewer needs to double check?
Shouldn't be any 👍 

## Why was this MR needed?
Improve GitLab usability on mobile devices

## Screenshots (if relevant)
Before:
![Simulator_Screen_Shot_Sep_13__2016__11.30.19_AM](/uploads/7053a1bb1fca6238c5f86d671bf96ff0/Simulator_Screen_Shot_Sep_13__2016__11.30.19_AM.png)

After:
![Simulator_Screen_Shot_Sep_13__2016__11.30.04_AM](/uploads/a30921c1a1118655b547977872e8e1c7/Simulator_Screen_Shot_Sep_13__2016__11.30.04_AM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #22097

See merge request !6325

Skip wiki creation when GitHub project has wiki enabled

## What does this MR do?

When importing a repository from if the repository has wiki, we should not create the default wiki. Otherwise the GitHub importer will fail because the wiki repository already exist. This bug was introduced here https://gitlab.com/gitlab-org/gitlab-ce/commit/892dea67717c0efbd6a28f7639f34535ec0a8747

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

No.

## Why was this MR needed?

GitLab fails to import GitHub Wiki.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [X] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [X] Added for this feature/bug
  - [ ] All builds are passing
- [X] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [X] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [X] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Fixes #22225

See merge request !6665

Adds v-pre to code blocks in comments

## What does this MR do?

Allows users to comment on discussions with code that contains `{{`

Previously because of the discussion part being a Vue app it was being converted by Vue & therefore creating JS errors & the code not displaying correctly. This adds `v-pre` onto the code element to allow the user to write code that would contain `{{`

## What are the relevant issue numbers?

Closes #22911

See merge request !6674

If the GitHub project repository has wiki, we should not create
the default wiki. Otherwise the GitHub importer will fail because
the wiki repository already exist.

This bug was introduced here
https://gitlab.com/gitlab-org/gitlab-ce/commit/892dea67717c0efbd6a28f763
9f34535ec0a8747

Update RuboCop to 0.43.0 and update configuration

`Style/VariableNumber` is explicitly disabled because I don't think we
care if we name a variable `var_1` or `var1`.

See merge request !6670

Restrict failed login attempts from users with 2FA enabled.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/19799.

See merge request !6668

Copy logic from `Devise::Models::Lockable#valid_for_authentication?`, as
our custom login flow with two pages doesn't call this method. This will
increment the failed login counter, and lock the user's account once
they exceed the number of failed attempts.

Also ensure that users who are locked can't continue to submit 2FA
codes.

Save a fetchable ref per deployement

cc @DouweM @ayufan

See merge request !6618

Closes #22911

Ensure the 'fixed layout' preference is honored whenever possible

## What does this MR do?

Currently, when viewing any Merge Request the user's fixed-layout preference is overridden if they have set "Side-by-Side" view as their preference when viewing diffs.  This makes sense if they are currently viewing a diff, but this is confusing when their layout preference is overridden while they are on another tab (i.e. "Discussion" or "Builds").

This MR moves all responsibility for overriding the fixed layout from the Ruby page layout helper into frontend JavaScript where it is only applied when needed.

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

Check that nothing broke for users which have their layout preference set to "Fluid" as well as those which have it set to "Fixed".  I've already done this but double checking is always good idea 😄.

## Screenshots (if relevant)

![side-by-side-toggle-fixed](/uploads/033dc73e70b73da5692b75606733c938/side-by-side-toggle-fixed.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #22343 

## Other Notes

As @lbennett noted in #22343, this is something of a band-aid.  It fixed most of the issue, but we still need to have a discussion about whether or not is acceptable to override user layout preferences for "Side-by-Side" views in general.  At least this MR limits the scope of this behavior to a single tab within an MR or merge conflict page.

See merge request !6422

`Style/VariableNumber` is explicitly disabled because I don't think we
care if we name a variable `var_1` or `var1`.

Fix bug when trying to cache closed issues from external issue trackers

fixes #22446

See merge request !6619

Upgrade acts-as-taggable-on from 3.5.0 to 4.0.0.

## What does this MR do?

Upgrades the acts-as-taggable-on gem from 3.5.0 to 4.0.0.

Changelog: https://github.com/mbleigh/acts-as-taggable-on/blob/master/CHANGELOG.md#400--2016-08-08

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

That this works without the migrations, I don't believe the upgrade from 3.5.0 to 4.0.0 requires any migrations since [UPGRADING.md hasn't been updated since 3.5.0 was released](https://github.com/mbleigh/acts-as-taggable-on/blob/master/UPGRADING.md). It's kind of unclear, unfortunately.

## What are the relevant issue numbers?

Fixes #22082. Working toward Rails 5: #14286.

cc: @dzaporozhets

See merge request !6660

Simplify Mentionable concern instance methods

## What does this MR do?

Simplify arguments received by the instance methods on the concern so in the closer future will be easy to understand and change

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

## Why was this MR needed?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !6596

Improve `Members::DestroyService`

Part of #21979.

See merge request !6267

Append issue template to existing description

## What does this MR do?

When selecting an issue template after entering a description, append the template and leave the original content intact.

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

Not that I'm aware of.

## Why was this MR needed?

The issue template shouldn't override the issue content without warning.

## Screenshots

![](https://i.imgur.com/E16X2tc.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master`
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/21733

See merge request !6149

Todo issue due date

## What does this MR do?

Adds the text 'Due today' or 'Due [DATE]' next to issues in todos.
This does not add anyway to filter by due date - little steps.

## What are the relevant issue numbers?

#18218

See merge request !6351

GrapeDSL for Namespace endpoint

No changelog item as it doesn't change behaviour

Cherry-picked from !6330

See merge request !6632

Fix issues importing services via Import/Export

Prevents errors when initialising services that do not have any properties set yet - case that could happen when importing projects.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/22891

See merge request !6667

We remove some arguments that are rarely used or 
used just to simplify setups on specs.

Modified Mentionable#create_new_cross_references method 
we don’t need to calculate previous references to avoid the 
duplication because we do that at database level when 
creating references extracted from the current entity state.

MergeRequests won’t create cross_references for commits that are included so we change a spec to use a different merge request to make references to commits to other branches

Add Container Registry on/off status to admin area

## What are the relevant issue numbers?

Closes #22805

See merge request !6638

Remove SCSS rules for short hex chars.

## What does this MR do?
Remove CSS hex shorthands linter
## Are there points in the code the reviewer needs to double check?
That I did it right. 
## Why was this MR needed?
To remove SCSS linter for hex shorthands
## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/22920

cc @connorshea

See merge request !6663

Changed mr widget build status to pipeline status

## What does this MR do?

Changed mr widget build status to pipeline status with pipeline id, with a link to the pipeline.

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

Do we want the link to the pipeline?

/cc @dimitrieh 

## Screenshots (if relevant)

![Screen_Shot_2016-09-14_at_02.42.23](/uploads/94a860361ab70eccf966e519764c6ec5/Screen_Shot_2016-09-14_at_02.42.23.png)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #22006

See merge request !6335