Refactor Gitlab::Identifier

## What does this MR do?

This refactors `Gitlab::Identifier` so that it:

1. Has tests
2. Caches output in an instance variable to reduce queries
3. Uses only a single query to find a user by an SSH key, instead of 2

## Why was this MR needed?

This code was untested and would execute more SQL queries than needed.

See merge request !6680

This refactors Gitlab::Identifier so it uses fewer queries and is
actually tested. Queries are reduced by caching the output as well as
using 1 query (instead of 2) to find a user using an SSH key.

Update runner version only when updating contacted_at

## What does this MR do?

Improves how we update runners table, especially the version.

This is another round of improvements to reduce number of `ci_runners` updates.

I did make `contacted_at` to be updated more often (on average every 15 minutes).
We will also update version information in one go to solve: https://gitlab.com/gitlab-org/gitlab-ce/issues/22206

Improves: https://gitlab.com/gitlab-org/gitlab-ce/issues/22590
Solves: https://gitlab.com/gitlab-org/gitlab-ce/issues/22206

See merge request !6537

Skipped jobs should be considered successful

## What does this MR do?

If all jobs in previous stage are all skipped, the next stage should consider previous stage succeeded.

## Why was this MR needed?

Since for now we consider all manual jobs if skipped, should not block the next stage from running.

Closes #22598 

See also #20342 (because this merge request conflicts with it)

See merge request !6604

Fix small typo in using_docker_images.md, file is called `build_script` (using underscore)

## What does this MR do?

This MR fixes a very small typo in the using_docker_images.md documentation, a space was used in the filename `build_script` while it should be an underscore. Not sure of a MR is the best way to get this changed, trying it anyway :).

## Moving docs to a new location?

No

See merge request !6682

Remove lease from Event#reset_project_activity

## What does this MR do?

This removes the exclusive lease used by `Event#reset_project_activity` in favour of conditional UPDATE queries. See dbcc623a901cb3fb725976217416bafad73dbf69 for more information.

## Why was this MR needed?

Obtaining the lease can, for whatever reason, be _really_ slow. See https://gitlab.com/gitlab-org/gitlab-ce/issues/22473 for more information.

https://gitlab.com/gitlab-org/gitlab-ce/issues/22473

See merge request !6678

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

Per GitLab.com's performance metrics this method could take up to 5
seconds of wall time to complete, while only taking 1-2 milliseconds of
CPU time. Removing the Redis lease in favour of conditional updates
allows us to work around this.

A slight drawback is that this allows for multiple threads/processes to
try and update the same row. However, only a single thread/process will
ever win since the UPDATE query uses a WHERE condition to only update
rows that were not updated in the last hour.

Fixes gitlab-org/gitlab-ce#22473

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

* upstream/master:
  Fixed banzai test failures
  Removed puts code 🙈
  Adds v-pre to code blocks in comments

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

* upstream/master: (55 commits)
  Restrict failed login attempts for users with 2FA
  Update RuboCop to 0.43.0 and update configuration
  Use SELECT 1, instead SELECT COUNT(*) to ask for notes existency
  Simplify Mentionable concern instance methods
  Fix issues importing services via Import/Export
  deployment refs in own folder, new method for creating refs
  Update method name
  Save a fetchable ref per deployement
  GrapeDSL for Namespace endpoint
  Remove SCSS rules for short hex chars.
  Fix bug when trying to cache closed issues from external issue trackers
  Upgrade acts-as-taggable-on from 3.5.0 to 4.0.0.
  Remove useless code now that Member#add_user handles it
  Combine requestFileSuccess arguments into `opts`
  Append issue template to existing description
  Invert method's naming
  Fix a few things after the initial improvment to Members::DestroyService
  Improve Members::DestroyService
  Add Container Registry on/off status to admin area
  Enable Lint/StringConversionInInterpolation cop and autocorrect offenses
  ...

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